RAIS Radionuclide Risk Calculator User's Guide

The purpose of this calculator is to assist Remedial Project Managers (RPMs), On Scene Coordinators (OSC’s), risk assessors and others involved in decision-making at hazardous waste sites and to determine whether levels of contamination found at the site may warrant further investigation or site cleanup, or whether no further investigation or action may be required.

The risk values presented on this site are radionuclide-specific values for individual contaminants in air, water, soil and biota that may warrant further investigation or site cleanup.

It should be noted that the risks in this calculator are based upon human health risk and do not address potential ecological risk. Some sites in sensitive ecological settings may also need to be evaluated for potential ecological risk. EPA's guidance "Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessment" contains an eight step process for using benchmarks for ecological effects in the remedy selection process. For ecological effects use the Ecological Benchmark tool on this site.

2.1 General Considerations

This portion of the risk assessment process is generally referred to as "Risk Characterization". This step incorporates the outcome of the previous activities and calculates the risk or hazard resulting from potential exposure to radionuclides via the pathways and routes of exposure determined appropriate for the source area.

The basic equation for calculating excess lifetime cancer risk is:

Risk = CDI × SF

where:

Risk = a unitless probability of an individual developing cancer over a lifetime;
CDI = chronic daily intake or dose [pCi, pCi-year/g, pCi-year/L, pCi-year/m³]
SF = slope factor, expressed in [risk/pCi or risk-g/pCi-year, risk-L/pCi-year, risk-m³/pCi-year]

The risk results are color coded to identify risk ranges and potential radionuclides of concern. The colors and the associated risk ranges are presented in the table below.

Excess Lifetime Cancer Risk
Risk Range	Risk < 0.000001	Risk > 0.000001	Risk > 0.0001
Color Code	No shading	Orange	Red

2.1.1 One-Hit Rule

The linear risk equation, listed above, are valid only at low risk levels (below estimated risks of 0.01). For sites where radiological exposure might be high (estimated risks above 0.01, an alternate calculation should be used. The one-hit equation, which is consistent with the linear low-dose model, should be used instead (RAGS, part A, ch. 8). The results presented on the RAIS use this rule. In the following instances, one-hit rule is used independently in our risk output tables:

Risk from a single exposure route for a single radionuclide.

Summation of single radionuclide risk (without one-hit rule applied to single radionuclide results) for multiple exposure routes (right of each row).

Summation of risk (without one-hit rule applied to single radionuclide results) from a single exposure route for multiple radionuclides (bottom of each column).

Summation of total risk (without one-hit rule applied to single radionuclide results or summations listed above) from multiple radionuclides across multiple exposure routes (bottom right hand cell).

2.2 Exposure Assumptions

Risks are based on default exposure parameters and factors that represent Reasonable Maximum Exposure (RME) conditions for long-term/chronic exposures and are based on the methods outlined in EPA’s Risk Assessment Guidance for Superfund, Part B Manual (1991) and Soil Screening Guidance documents (1996 and 2002).

Site-specific information may warrant modifying the default parameters in the equations and calculating site-specific risks. In completing such calculations, the user should answer some fundamental questions about the site. For example, information is needed on the contaminants detected at the site, the land use, impacted media and the likely pathways for human exposure.

Whether these generic risks or site-specific risks are used, it is important to clearly demonstrate the equations and exposure parameters used in deriving risks at a site. A discussion of the assumptions used in the risk calculations should be included in the decision document for a CERCLA site.

2.3 Slope Factors (SFs)

EPA classifies all radionuclides as Group A carcinogens ("carcinogenic to humans"). Group A classification is used only when there is sufficient evidence from epidemiologic studies to support a causal association between exposure to the agents and cancer. The appendix radionuclide table, from the Center for Radiation Protection Knowledge, lists ingestion, inhalation and external exposure cancer slope factors (risk coefficients for total cancer morbidity) for radionuclides in conventional units of picocuries (pCi). Ingestion and inhalation slope factors are central estimates in a linear model of the age-averaged, lifetime attributable radiation cancer incidence (fatal and nonfatal cancer) risk per unit of activity inhaled or ingested, expressed as risk/pCi. External exposure slope factors are central estimates of lifetime attributable radiation cancer incidence risk for each year of exposure to external radiation from photon-emitting radionuclides distributed uniformly in a thick layer of soil and are expressed as risk/yr per pCi/gram soil. External exposure slope factors can also be used which have units of risk/yr per pCi/cm² soil. When combined with site-specific media concentration data and appropriate exposure assumptions, slope factors can be used to estimate lifetime cancer risks to members of the general population due to radionuclide exposures. EPA currently provides guidance on inhalation risk assessment in RAGS Part F (Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment). This guidance only addresses chemicals. The development of inhalation slope factors for radionuclides differs from the guidance presented in RAGS Part F for development of inhalation unit risk (IUR) values for chemicals.

The SFs from the Center for Radiation Protection Knowledge differ from the values presented in HEAST. The SFs were calculated using ORNL's DCAL software in the manner of Federal Guidance Report 12 and 13. The radionuclides presented are those provided in the International Commission on Radiological Protection (ICRP) Publication 107. This document contains a revised database of nuclear decay data (energies and intensities of emitted radiations, physical half-lives and decay modes) for 1,252 naturally occurring and manmade radionuclides. ICRP Publication 107 supersedes the previous database, ICRP Publication 38 published in 1983. In addition to radionuclides in ICRP Publication 107, the assembled data files or tables contain entries that include the contribution of daughter products in secular equilibrium with their longer-lived parents. These entries are identified by the addition of "+D" and to the nuclide name where "+D" refers to a 100 year period of progeny ingrowth.

2.3.1 When To Use "+D" Risk Exposure Models

Several of the isotopes are listed with a '+D' designation. This designation indicates that the slope factor includes the contribution from ingrowth of daughter isotopes out to 100 years. The intention of this designation is to make realistic risks by including the contributions from their short-lived decay products. The +D designation indicates that the parent radionuclide is accompanied by its progeny. In general, the activity of chain members assumes progeny ingrowth of 100 years. There is one exception for the inhalation slope factor for Rn-222+D. EPA assumes a 50% equilibrium value for radon decay products (Po-218, Pb-214, Bi-214 and Po-214) in air. Before applying risks to a site, it should be determined if the isotopes present are in secular equilibrium. If the isotopes are found to be in secular equilibrium, the +D risks should be used for the parent isotope and the daughters included in the +D can be ignored. If the isotopes are not in secular equilibrium, risks should be applied individually for each daughter isotope. However, in the absence of empirical data, the "+D" values for radionuclides should be used unless there are compelling reasons not to.

For example, if analytical data from a site reveal that Ra-226, Rn-222 and Po-218 are detected at a site and that they are in secular equilibrium, the risk for Ra-226+D should be applied and the Rn-222 and Po-218 can be ignored.

Another example could concern a decay chain in secular equilibrium like Th-228. Even though the decay chain for Th-228 is long, there is no Th-228+D slope factor because the activity of any of the progeny after 100 years of chain ingrowth was less than 90% of the parent's activity. The general rule for non-branching chains is, if a parent has any progeny with greater than 90% of the parent's activity at 100 years, a +D is calculated. For branching chains, if any branch contributes over 90% of the branch fraction activity, at 100 years, a +D is calculated. An example of this would be Cs-137+D where the branching fraction is 94.4 % to Ba-137m and at 100 years Ba-137m contributes over 90% of the activity than the parent, Cs-137. In either chain type, if the total dose contribution of the progeny is insignificant relative to the parent's contribution, then no +D values are calculated.

In this case of Th-228, the risks for Th-228, Ra-224+D, Po-216, Pb-212, Bi-212+D and Tl-208 should be used. If no part of the decay chain is in secular equilibrium, the user should use each of the risks for isotopes in the decay chain that have slope factors (e.g., Ra-224, Rn-220, Po-216, Pb-212, Bi-212, Po-212, and Tl-208). If part of the decay chain is in secular equilibrium, then the user may use that particular +D slope factor that covers that part of the decay chain, while using the slope factors for the other radionuclides.

2.3.2 Associated Decay Chains for "+D" Risk Exposure Models

Selected radionuclides and radioactive decay chain products are designated with the suffix "+D" to indicate that cancer risk estimates for these radionuclides include the contributions from their short-lived decay products, assuming equal activity concentrations (i.e., secular equilibrium) with the principal or parent nuclide in the environment. For all radionuclides without the "+D" suffix, only intake or external exposure to the single radionuclide is considered. Most radionuclides with a +D designation include the entire decay chain to the stable terminal nuclide in the slope factors. The Center for Radiation Protection Knowledge provides a table of the 100 year progeny ingrowth for the isotopes in Table 2 of Appendix A of Calculations of Slope Factors and Dose Coefficients. This table provides the associated decay chain used in the slope factors. This table is reproduced below for common isotopes with the terminal nuclide added.

Principal Radionuclide (half-life in years)	Associated decay chain	Terminal Radionuclide	Half-life (yr)
Cs-137+D (30.2)	Ba-137m	Ba-137	stable
Pu-239+D (2.41E+04)	U-235m	U-235	7.04E+08
Ra-226+D (1.60E+03)	Rn-222, Po-218, Pb-214, At-218, Bi-214, Rn-218, Po-214, Tl-210	Pb-210	22
Ra-228+D (5.75E+00)	Ac-228	Th-228	2
Rn-222+D (1.05E-02)	Po-218	Pb-214	5.10E-05
Sr-90+D (28.8)	Y-90	Zr-90	stable
Th-232+D (1.41E+10)	Ra-228, Ac-228	Th-228	1.91E+00
U-235+D (7.04E+08)	Th-231	Pa-231	3.3E+04
U-238+D (4.47E+09)	Th-234, Pa-234m, Pa-234	U-234	2.4E+05

2.3.3 Metastable Isotopes

Most dose and risk coefficients are presented for radionuclides in their ground state. In the decay process, the newly formed nucleus may be in an excited state and emit radiation; e.g., gamma rays, to lose the energy of the state. The excited nucleus is said to be in a metastable state which is denoted by the chemical symbol and atomic number appended by "m"; e.g., Ba-137m. If additional higher energy metastable states are present then "n", "p", ... is appended. Metastable states have different physical half-lives and emit different radiations and thus unique dose and risk coefficients. In decay data tabulations of ICRP 107), if the half-life of a metastable state was less than 1 minute then the radiations emitted in de-excitation are included with those of the parent radionuclide. Click to see a graphical representation of the decay of Cs-137 to Ba-137.

Eu-152, in addition to its ground state has two metastable states: Eu-152m and Eu-152n. The half-lives of Eu-152, Eu-152m and Eu-152n are: 13.5 y, 9.31 m and 96 m, respectively and the energy emitted per decay is 1.30 MeV, 0.080 MeV, and 0.14 MeV, respectively.

2.4 Radionuclide-specific Parameters

Several radionuclide-specific parameters are needed for development of the risks. The parameters are selected from a hierarchy of sources.

2.4.1 Sources

Many sources are used to populate the database of radionuclide-specific parameters. They are briefly described below.

1. IAEA TRS 472 (IAEA). Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Terrestrial and Freshwater Environments. Technical Reports Series No. 472. International Atomic Energy Agency, Vienna. 2010. (IAEA TRS 364. Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments (Technical Reports Series No. 364), 1994 was used to supplement egg, poultry and swine transfer factors.) Spreadsheet of values.
2. NCRP 123 (NCRP). NCRP Report No. 123, Screening Models for Releases of Radionuclides to the Atmosphere, Surface Water, and Ground. National Council on Radiation Protection and Measurements. January 22, 1996. Spreadsheet of values.
3. EPA Radionuclide Soil Screening Level (SSL). Soil Screening Guidance for Radionuclides: User's Guide. Office of Solid Waste and Emergency Response (OSWER) Directive 9355.4-16A. October 2000. Spreadsheet of values.
4. RESRAD. User's Manual for RESRAD Version 6. Environmental Assessment Division, Argonne National Laboratory. July 2001. Spreadsheet of values.
5. BAES. A Review and Analysis of Parameters for Assessing Transport of Environmentally Released Radionuclides through Agriculture. C. F. Baes III, R. D. Sharp, A. L. Sjoreen, R.W. Shor. Oak Ridge National Laboratory 1984. Spreadsheet of values.
6. ICRP 107. Nuclear Decay Data for Dosimetric Calculations. International Commission on Radiological Protection Publication 107. Ann. ICRP 38 (3), 2008.
7. EPAKD. Understanding Variation in Partition Coefficient, Kd, Values. Volume II: Review of Geochemistry and Available Kd Values for Cadmium, Cesium, Chromium, Lead, Plutonium, Radon, Strontium, Thorium, Tritium (3H), and Uranium. Office of Air and Radiation. EPA 402-R-99-004B. August 1999. and Volume III: Review of Geochemistry and Available Kd Values for Americium, Arsenic, Curium, Iodine, Neptunium, Radium, and Technetium. Office of Air and Radiation. EPA 402-R-04-002C. July 2004. Spreadsheet of values.

2.4.2 Hierarchy by Parameter

Generally the hierarchies below are followed.

1. Half-life (yr), Decay mode, Atomic weight, Atomic number and Decay energy. ICRP 107.
2. Milk transfer factor (TF_dairy (day/L). IAEA, NCRP, RESRAD, BAES. TF_dairy is the volumetric activity density in milk (pCi/L) divided by the daily intake of radionuclide (pCi/day).
3. Beef transfer factor (TF_beef (day/kg). IAEA, NCRP, RESRAD, BAES. TF_beef is the mass activity density in beef (pCi/kg fresh weight) divided by the daily intake of radionuclide (in pCi/d).
4. Fish bioconcentration factor (BCF (L/kg). IAEA, RESRAD. BCF is the ratio of the radionuclide concentration in the fish tissue (pCi/kg fresh weight) from all exposure pathways relative to that in water (pCi/L).
5. Poultry transfer factor (TF_poultry (day/kg). IAEA, RESRAD. TF_poultry is the mass activity density in poultry (pCi/kg fresh weight) divided by the daily intake of radionuclide (in pCi/d).
6. Egg transfer factor (TF_egg (day/kg). IAEA, RESRAD. TF_egg is the mass activity density in egg (pCi/kg fresh weight) divided by the daily intake of radionuclide (in pCi/d).
7. Swine transfer factor (TF_swine (day/kg). IAEA, RESRAD. TF_swine is the mass activity density in swine (pCi/kg fresh weight) divided by the daily intake of radionuclide (in pCi/d).
8. Soil to water partition coefficient (K_d (mg/kg-soil per mg/L water or simplified = L/kg). EPAKD, IAEA, SSL, RESRAD, BAES. (K_d is the ratio of the mass activity density (pCi/kg) of the specified solid phase (usually on a dry mass basis) to the volumetric activity density (Bq/L) of the specified liquid phase.
9. Soil to plant transfer factor-wet (Bv_wet (pCi/g plant per pCi/g soil). IAEA, NCRP, SSL, RESRAD, BAES. The values for cereal grain are used from IAEA. (Bv_wet is the ratio of the activity concentration of radionuclide in the plant (pCi/kg wet mass) to that in the soil (pCi/kg dry mass). Note: Some Bv_wet values were derived from Bv_dry sources, assuming the ratio of dry mass to fresh mass was presented in the source documents.
10. Soil to plant transfer factor-dry (Bv_dry (pCi/g plant per pCi/g soil). IAEA, NCRP, SSL, RESRAD, BAES. The values for cereal grain are used. (Bv_dry is the ratio of the activity concentration of radionuclide in the plant (pCi/kg dry mass) to that in the soil (pCi/kg dry mass). Note: Some Bv_dry values were derived from Bv_wet sources, assuming the ratio of dry mass to fresh mass was presented in the source documents.


Bv_wet and Bv_dry can be determined using the following equations.


and:

The risk calculator provides generic concentrations in the absence of site-specific exposure assessments. These concentrations can be used for:

Prioritizing multiple sites within a facility or exposure units

Setting risk-based detection limits for contaminants of potential concern (COPCs)

Focusing future risk assessment efforts

When appropriate for the site, consideration as risk-based cleanup levels

3.1 Developing a Conceptual Site Model

When using risks, the exposure pathways of concern and site conditions should match those taken into account by the screening levels. (Note, however, that future uses may not match current uses. Future uses of a site should be logical as conditions which might occur at the site in the future.) Thus, it is necessary to develop a conceptual site model (CSM) to identify likely contaminant source areas, exposure pathways, and potential receptors. This information can be used to determine the applicability of screening levels at the site and the need for additional information. The final CSM diagram represents linkages among contaminant sources, release mechanisms, exposure pathways, and routes and receptors based on historical information. It summarizes the understanding of the contamination problem. A separate CSM for ecological receptors can be useful. Part 2 and Attachment A of the Soil Screening Guidance for Radionuclides: Users Guide (EPA 2000a) contains the steps for developing a CSM.

As a final check, the CSM should answer the following questions:

A conceptual site model for the land uses presented in this calculator is presented below.

Are there potential ecological concerns?

Is there potential for land use other than those listed in the risk calculator (i.e. , residential and industrial)?

Are there other likely human exposure pathways that were not considered in development of the risks?

Are there unusual site conditions (e.g. large areas of contamination, high fugitive dust levels, potential for indoor air contamination)?

The risks may need to be adjusted to reflect the answers to these questions.

3.2 Background Radiation

Natural background radiation should be considered prior to applying risks as cleanup levels. Background and site-related levels of radiation will be addressed as they are for other contaminants at CERCLA sites. For further information, see EPA's guidance "Role of Background in the CERCLA Cleanup Program", April 2002, (OSWER 9285.6-07P). It should be noted that certain ARARs specifically address how to factor background into cleanup levels. For example, some radiation ARAR levels are established as increments above background concentrations. In these circumstances, background should be addressed in the manner prescribed by the ARAR.

3.3 Potential Problems and Limitations

As with any risk based tool, the potential exists for misapplication. In most cases, this results from not understanding the intended use of the risks. In order to prevent misuse of the risks, the following should be avoided:

Applying risk levels to a site without adequately developing a conceptual site model that identifies relevant exposure pathways and exposure scenarios.

Use of risk levels as cleanup levels without the consideration of other relevant criteria such as ARARs.

Use of risk levels as cleanup levels without verifying numbers with a health physicist/risk assessor.

Use of outdated risk levels tables that have been superseded by more recent publications.

Not considering the effects from the presence of multiple isotopes.

The chronic daily intake (CDI) equations consider human exposure to individual contaminants in air, water, soil, sediment and biota. The technical discussion is aimed at producing risk results. The following text presents the land use equations and their exposure routes. The tables at the end of the users guide present the definitions of the variables and their default values. Any alternative values or assumptions used in developing risks on a site should be presented with supporting rationale in the decision documents.

The risk equations have evolved over time and are a combination of the following guidance documents:

Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part B, Development of Risk-based Preliminary Remediation Goals) (RAGS Part B).

U.S. EPA. 2005. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. Washington, DC. OSWER No. 5305W. EPA530-R-05-006

U.S. EPA. 2000a. Soil Screening Guidance for Radionuclides: User's Guide. Office of Emergency and Remedial Response and Office of Radiation and Indoor Air. Washington, DC. OSWER No. 9355.4-16A EPA/540-R-00-007

U.S. EPA. 2000b. Soil Screening Guidance for Radionuclides: Technical Background Document. Office of Emergency and Remedial Response and Office of Radiation and Indoor Air. Washington, DC. OSWER No. 9355.4-16

U.S. EPA 2002. Supplemental Guidance for Developing Soil Screening Levels for Superfund Sites. OSWER 9355.4-24. December 2002.

U.S. EPA 1994b. Radiation Site Cleanup Regulations: Technical Support Documents for the Development of Radiation Cleanup Levels for Soil - Review Draft. Office of Radiation and Indoor Air, Washington, DC. EPA 402-R-96-011A. PDF document View Appendix C here.

U.S. EPA. 1994c. Revised Draft Guidance for Performing Screening Level Risk Analyses at Combustion Facilities Burning Hazardous Wastes. Attachment C. Office of Emergency and Remedial Response. Office of Solid Waste. December 14.

U.S. EPA. 1996a. Soil Screening Guidance: User's Guide. Office of Emergency and Remedial Response. Washington, DC. OSWER No. 9355.4-23

U.S. EPA. 1996b. Soil Screening Guidance: Technical Background Document. Office of Emergency and Remedial Response. Washington, DC. OSWER No. 9355.4-17A

U.S. EPA. 1998. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. Office of Solid Waste, Washington, DC. EPA530-D-98-001A. A secure PDF can be downloaded here.

NCRP 1996. Screening Models for Releases of Radionuclides to Atmosphere, Surface Water, and Ground, Vols. 1 and 2, NCRP Report No. 123. National Council on Radiation Protection and Measurements.

4.1 Resident

4.1.1 Resident Soil

This receptor spends most, if not all, of the day at home except for the hours spent at work. The activities for this receptor involve typical home making chores (cooking, cleaning and laundering) as well as gardening. The resident is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust and consumption of home grown produce (100% of fruit and vegetables). Adults and children exhibit different ingestion rates for soil and produce. For example the child resident is assumed to ingest 200 mg per day while the adult ingests 100 mg per day. To take into account the different intake rate for children and adults, age adjusted intake equations were developed to account for changes in intake as the receptor ages.

Graphical Representation

Equations

The residential soil land use equations, presented here, contain the following exposure routes:

incidental ingestion of soil,

inhalation of particulates emitted from soil and

external exposure to ionizing radiation.

ingestion of soil from the direct ingestion of produce.

direct ingestion of produce.

4.1.2 Resident Soil Alternate External Exposure Analysis

This receptor spends most, if not all, of the day at home except for the hours spent at work. The activities for this receptor involve typical home making chores (cooking, cleaning and laundering) as well as gardening.

This analysis is designed to look at external exposure from contamination of different area sizes. Areas considered are 1 to 1,000,000 square meters. Isotope-specific area correction factor (ACF) were developed for this analysis.

Graphical Representation

Equations

Direct External Exposure to contamination at infinite depth

Direct External Exposure to contamination at 1 cm

Direct External Exposure to contamination at 5 cm

Direct External Exposure to contamination at 15 cm

Direct External Exposure to contamination dust

4.1.3 Resident Air

This receptor spends most, if not all, of the day at home except for the hours spent at work. The activities for this receptor involve typical home making chores (cooking, cleaning and laundering) as well as gardening. The resident is assumed to be exposed to contaminants via the following pathways: inhalation of ambient air and external radiation from contaminants in ambient air. To take into account the different inhalation rates for children and adults, age-adjusted intake equations were developed to account for changes in intake as the receptor ages.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The residential ambient air land use equation, presented here, contains the following exposure routes with half-life decay:

inhalation with decay.

submersion with decay.

Without Decay

The residential ambient air land use equation, presented here, contains the following exposure routes without half-life decay:

inhalation without decay.

submersion without decay.

4.1.4 Resident Tap Water

This receptor is exposed to radionuclides that are delivered into a residence. Ingestion of drinking water is an appropriate pathway for all radionuclides. Activities such as showering, laundering, and dish washing also contribute to inhalation. The inhalation exposure route is only calculated for C-14, H-3, Rn-220, and Rn-222 which volatilize. External exposure to immersion in tap water and exposure to produce irrigated with contaminated tap water are also considered. The submersion route is also included for radioactive gases in tapwater. This addition was based on research found in ORNL/TM-2023/3001 - Quantifying the Impact of the Exclusion of the Submersion Exposure Route in Soil and Tap Water Models in Existing Superfund Radionuclide Screening Level Calculators.

Graphical Representation

Equations

The tap water land use equation, presented here, contains the following exposure routes:

ingestion of water

inhalation of volatiles (The inhalation exposure route is only calculated for C-14, H-3, Rn-220, Rn-222, and Rn-222+D). Also, volatilization in the equation comes from household uses of water (e.g., showering, laundering, dish washing)

submersion in volatiles (The submersion exposure route is only calculated for C-14, H-3, Rn-220, Rn-222, and Rn-222+D). Also, volatilization in the equation comes from household uses of water (e.g., showering, laundering, dish washing)

immersion in water

ingestion of tap water from direct ingestion of produce.

direct ingestion of produce.

4.1.5 Consumption of Fish

The risk from consumption of fish is represented here. This is unlike the farmer scenario where the risk is calculated for soil levels protective of fish consumption. Further the ingestion rate is not age adjusted like the farmer scenario.

Graphical Representation

Equations

The consumption of fish equation, presented here, contains the following exposure routes:

Consumption of fish, concentration in fish.

consumption of fish. Concentration in Surface water.

Note: the consumption rate for fish is not age adjusted for this land use. Also the CDI calculated for fish is not for soil, like for the agricultural land uses, but is for fish tissue.

4.1.6 Soil to Groundwater

The soil to groundwater media uses the same water concentration determination equations for resident and indoor worker based on the respective soil concentration entered by the user for each land use. The graphical representation below illustrates the transport of contaminants from soil to groundwater for the resident land use. For more information about soil to groundwater, including equation images, please see section 4.9 of this user guide.

Graphical Representation

4.2 Indoor Worker

4.2.1 Indoor Worker Soil

This receptor spends most, if not all, of the workday indoors. Thus, an indoor worker has no direct contact with outdoor soils. This worker may, however, be exposed to contaminants through ingestion of contaminated soils that have been incorporated into indoor dust, external radiation from contaminants in soil, and the inhalation of contaminants present in indoor air. Risks calculated for this receptor are for both workers engaged in low intensity activities such as office work and those engaged in more strenuous activity (e.g., factory or warehouse workers).

Graphical Representation

Equations

The indoor worker soil land use equations, presented here, contain the following exposure routes:

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation.

4.2.2 Indoor Worker Soil Alternate External Exposure Analysis

This receptor spends most, if not all, of the workday indoors. Thus, an indoor worker has no direct contact with outdoor soils. A gamma shielding factor is applied for this scenario to account for shielding provided by floors and foundation slabs.

This analysis is designed to look at external exposure from contamination of different area sizes. Areas considered are 1 to 1,000,000 square meters. Isotope-specific area correction factor (ACF) were developed for this analysis.

Graphical Representation

Equations

Direct External Exposure to contamination at infinite depth

Direct External Exposure to contamination at 1 cm

Direct External Exposure to contamination at 5 cm

Direct External Exposure to contamination at 15 cm

Direct External Exposure to contamination dust

4.2.3 Indoor Worker Air

This is a long-term receptor exposed during the work day who is a full time employee working on-site who spends most, if not all, of the workday indoors. The indoor worker is assumed to be exposed to contaminants via the following pathways: inhalation of ambient air and external radiation from contaminants in ambient air.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The indoor worker ambient air land use equation, presented here, contains the following exposure routes with half-life decay:

inhalation and

submersion.

With Decay

The indoor worker ambient air land use equation, presented here, contains the following exposure routes with half-life decay:

inhalation and

submersion.

4.2.4 Indoor Worker Tap Water

This receptor spends most, if not all, of the workday indoors. This worker may be exposed to contaminants in tap water water. The worker may drink the water, take a shower, and inhale water vapors while showering or as part of industrial operations. Risks calculated for this receptor are for both workers engaged in low intensity activities such as office work and those engaged in more strenuous activity (e.g., factory or warehouse workers). The submersion route is also included for radioactive gases in tapwater. This addition was based on research found in ORNL/TM-2023/3001 - Quantifying the Impact of the Exclusion of the Submersion Exposure Route in Soil and Tap Water Models in Existing Superfund Radionuclide Screening Level Calculators.

The indoor worker tap water land use equation, presented here, contains the following exposure routes:

Graphical Representation

Equations

The tap water land use equation, presented here, contains the following exposure routes:

ingestion of water and

inhalation, (The inhalation exposure route is only calculated for C-14, H-3, Rn-220, Rn-222, and Rn-222+D). Also, volatilization in the equation comes from household uses of water (e.g., showering, laundering, dish washing)

submersion, (The submersion exposure route is only calculated for C-14, H-3, Rn-220, Rn-222, and Rn-222+D). Also, volatilization in the equation comes from household uses of water (e.g., showering, laundering, dish washing)

external exposure.

4.2.5 Soil to Groundwater

The soil to groundwater media uses the same water concentration determination equations for resident and indoor worker based on the respective soil concentration entered by the user for each land use. The graphical representation below illustrates the transport of contaminants from soil to groundwater for the indoor worker land use. For more information about soil to groundwater, including equation images, please see section 4.9 of this user guide.

Graphical Representation

4.3 Outdoor Worker

4.3.1 Outdoor Worker Soil

This is a long-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., moderate digging, landscaping) typically involve on-site exposures to surface soils. The outdoor worker is expected to have an elevated soil ingestion rate (100 mg per day) and is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust. The outdoor worker receives more exposure than the indoor worker under commercial/industrial conditions.

Graphical Representation

Equations

The outdoor worker soil land use equations, presented here, contain the following exposure routes:

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation.

4.3.2 Outdoor Worker Soil Alternate External Exposure Analysis

This is a long-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., moderate digging, landscaping) typically involve on-site exposures to surface soils.

This analysis is designed to look at external exposure from contamination of different area sizes. Areas considered are 1 to 1,000,000 square meters. Isotope-specific area correction factor (ACF) were developed for this analysis.

Graphical Representation

Equations

Direct External Exposure to contamination at infinite depth

Direct External Exposure to contamination at 1 cm

Direct External Exposure to contamination at 5 cm

Direct External Exposure to contamination at 15 cm

Direct External Exposure to contamination dust

4.3.3 Outdoor Worker Air

This is a long-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., moderate digging, landscaping) typically involve on-site exposures to surface soils. The outdoor worker is assumed to be exposed to contaminants via the following pathways: inhalation of ambient air and external radiation from contaminants in ambient air.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The outdoor worker ambient air land use equation, presented here, contains the following exposure routes with half-life decay:

inhalation and

submersion.

Without Decay

The outdoor worker ambient air land use equation, presented here, contains the following exposure routes without half-life decay:

inhalation and

submersion.

4.4 Composite Worker

4.4.1 Composite Worker Soil

This is a long-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., moderate digging, landscaping) typically involve on-site exposures to surface soils. The composite worker is expected to have an elevated soil ingestion rate (100 mg per day) and is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust . The composite worker combines the most protective exposure assumptions of the outdoor and indoor workers. The only difference between the outdoor worker and the composite worker is that the composite worker uses the more protective exposure frequency of 250 days/year from the indoor worker scenario.

Graphical Representation

Equations

The composite worker soil land use equations, presented here, contain the following exposure routes:

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation.

4.4.2 Composite Worker Soil Alternate External Exposure Analysis

This is a long-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., moderate digging, landscaping) typically involve on-site exposures to surface soils.

This analysis is designed to look at external exposure from contamination of different area sizes. Areas considered are 1 to 1,000,000 square meters. Isotope-specific area correction factor (ACF) were developed for this analysis.

Graphical Representation

Equations

Direct External Exposure to contamination at infinite depth

Direct External Exposure to contamination at 1 cm

Direct External Exposure to contamination at 5 cm

Direct External Exposure to contamination at 15 cm

Direct External Exposure to contamination dust

4.4.3 Composite Worker Air

This is a long-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., moderate digging, landscaping) typically involve on-site exposures to surface soils. The composite worker is assumed to be exposed to contaminants via the following pathways: inhalation of ambient air and external radiation from contaminants in ambient air. The composite worker combines the most protective exposure assumptions of the outdoor and indoor workers. The only difference between the outdoor worker and the composite worker is that the composite worker uses the more protective exposure frequency of 250 days/year from the indoor worker scenario.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The composite worker ambient air land use equations, presented here, contain the following exposure routes with half-life decay:

inhalation and

submersion.

Without Decay

The composite worker ambient air land use equation, presented here, contains the following exposure routes without half-life decay:

inhalation and

submersion.

4.5 Excavation Worker

4.5.1 Excavation Worker Soil

The excavation worker soil land use has been historically presented on the RAIS and despite the addition of the more recent construction worker scenarios in the following sections, the land use is presented for verification of previous risk assessments.

This is a short-term receptor exposed during the work day. The activities for this receptor (e.g., trenching, excavating) typically involve on-site exposures to surface soils. The excavation worker is expected to have an elevated soil ingestion rate (330 mg per day) and is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust. The only difference between the excavation worker and the constriction worker described in section 4.6 is that the excavation worker uses a wind-driven PEF.

Graphical Representation

Equations

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation.

4.5.2 Excavation Worker Air

This is a short-term receptor exposed during the work day during heavy construction activities outdoors. The activities for this receptor (e.g., trenching, excavating) typically involve on-site exposures to surface soils. The construction worker is assumed to be exposed to contaminants via the following pathways: inhalation of ambient air and external radiation from contaminants in ambient air.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The excavation worker ambient air land use equations, presented here, contain the following exposure routes with half-life decay:

inhalation and

external exposure to ionizing radiation

Without Decay

The composite worker ambient air land use equation, presented here, contains the following exposure routes without half-life decay:

inhalation and

external exposure to ionizing radiation

4.6 Construction Worker

4.6.1 Construction Worker Soil exposure to Unpaved Road Traffic

This is a short-term receptor exposed during the work day working around vehicles suspending dust in the air. The activities for this receptor (e.g., trenching, excavating) typically involve on-site exposures to surface soils. The construction worker is expected to have an elevated soil ingestion rate (330 mg per day) and is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust. The only difference between this construction worker and the one described in section 4.12 is that this construction worker uses a different PEF.

The construction worker land use is described in the supplemental soil screening guidance. This land use is limited to an exposure duration of 1 year and is thus, subchronic. Other unique aspects of this scenario are that the PEF is based on mechanical disturbance of the soil. Two types of mechanical soil disturbance are addressed: standard vehicle traffic (e.g., trenching, excavating) and other than standard vehicle traffic (e.g. wind, grading, dozing, tilling and excavating). In general, the intakes and contact rates are all greater than the outdoor worker. Exhibit 5-1 in the supplemental soil screening guidance presents the exposure parameters.

Graphical Representation

Equations

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation.

4.6.2 Construction Worker Soil Exposure to Other Than Unpaved Road Traffic

This is a short-term receptor exposed during the work day working around heavy vehicles suspending dust in the air. The activities for this receptor (e.g., dozing, grading, tilling, dumping, excavating) typically involve on-site exposures to surface soils. The construction worker is expected to have an elevated soil ingestion rate (330 mg per day) and is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust. The only difference between this construction worker and the one described in section 4.6.1 is that this construction worker uses a different PEF.

The construction land use is described in the supplemental soil screening guidance. This land use is limited to an exposure duration of 1 year and is thus, subchronic. Other unique aspects of this scenario are that the PEF is based on mechanical disturbance of the soil. Two types of mechanical soil disturbance are addressed: standard vehicle traffic (e.g., trenching, excavating) and other than standard vehicle traffic (e.g. wind, grading, dozing, tilling and excavating). In general, the intakes and contact rates are all greater than the outdoor worker. Exhibit 5-1 in the supplemental soil screening guidance presents the exposure parameters.

Graphical Representation

Equations

The construction worker soil land use equations, presented here, contain the following exposure routes:

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation

4.6.3 Construction Worker Soil Alternate External Exposure Analysis

This is a short-term receptor exposed during the work day who is a full time employee working on-site and who spends most of the workday conducting maintenance activities outdoors. The activities for this receptor (e.g., trenching, excavating, wind, grading, dozing, and tilling) typically involve on-site exposures to surface soils.

This analysis is designed to look at external exposure from contamination of different area sizes. Areas considered are 1 to 1,000,000 square meters. Isotope-specific area correction factor (ACF) were developed for this analysis.

Graphical Representation

Equations

Direct External Exposure to contamination at infinite depth

Direct External Exposure to contamination at 1 cm

Direct External Exposure to contamination at 5 cm

Direct External Exposure to contamination at 15 cm

Direct External Exposure to contamination dust

4.6.4 Construction Worker Air

This is a short-term receptor exposed during the work day during heavy construction activities outdoors. The activities for this receptor (e.g., trenching, excavating, wind, grading, dozing, and tilling) typically involve on-site exposures to surface soils. The construction worker is assumed to be exposed to contaminants via the following pathways: inhalation of ambient air and external radiation from contaminants in ambient air.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The construction worker ambient air land use equations, presented here, contain the following exposure routes with half-life decay:

inhalation and

submersion.

Without Decay

The composite worker ambient air land use equation, presented here, contains the following exposure routes without half-life decay:

inhalation and

submersion.

4.7 Recreator

4.7.1 Recreator Soil

This receptor spends time outside involved in recreational activities. The recreator is assumed to be exposed to contaminants via the following pathways: incidental ingestion of soil, external exposure, and inhalation of fugitive dust. The exposure time and frequency are reasonable estimates based on weekend activities during the warmest 9 months of the year equating to about 75 days per year.

Graphical Representation

Equations

The recreational soil land use equations, presented here, contain the following exposure routes:

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

external exposure to ionizing radiation.

consumption of fowl - back-calculated to soil

consumption of game - back-calculated to soil

4.7.2 Recreator Soil Alternate External Exposure Analysis

This receptor spends time outside involved in recreational activities.

This analysis is designed to look at external exposure from contamination of different area sizes. Areas considered are 1 to 1,000,000 square meters. Isotope-specific area correction factors (ACF) were developed for this analysis.

Graphical Representation

Equations

Direct External Exposure to contamination at infinite depth

Direct External Exposure to contamination at 1 cm

Direct External Exposure to contamination at 5 cm

Direct External Exposure to contamination at 15 cm

Direct External Exposure to contamination dust

4.7.3 Recreator Air

This receptor spends time involved in recreational activities.

Two ambient air exposure conditions are offered for this scenario. The first scenario includes a half-life decay function and the second scenario does not. In situations where the contaminant in the air is not being replenished (e.g., an accidental one-time air release from a factory), equations for the first scenario should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil, or an operating factory or landfill cap), equations for the second scenario should be used.

Graphical Representation

Equations

With Decay

The recreator ambient air land use equation, presented here, contains the following exposure routes with half-life decay:

inhalation and

submersion.

Without Decay

The recreator ambient air land use equation, presented here, contains the following exposure routes without half-life decay:

inhalation and

submersion.

4.7.4 Recreator Consumption of Fowl and Game

This receptor spends time involved in recreational hunting of waterfowl and land game.

Graphical Representation

Equations

The consumption of fowl and game equations, presented here, contain the following exposure routes:

consumption of fowl - direct

consumption of land game - direct

4.7.5 Recreator Surface Water

This receptor is exposed to radionuclides that are present in surface water. Ingestion of water and immersion in water are appropriate pathways for all radionuclides. Inhalation is not considered due to mixing with outdoor air. The exposure time and events per day are reasonable estimates.

Graphical Representation

Equations

The surface water land use equation, presented here, contains the following exposure route:

ingestion of surface water.

immersion in surface water.

consumption of fowl - back-calculated to water

consumption of game - back-calculated to water

4.8 Farmer

4.8.1 Farmer Direct Consumption of Agricultural Products

The farmer scenario should be considered an extension of the resident scenario and evaluate consumption of farm products for a subsistence farmer. Like the resident, the farmer assumes the receptor will be exposed via the consumption of home grown produce (100% of fruit and vegetables are from the farm). In addition to produce, 100% of consumption of the following are also considered to be from the farm: beef, milk, fish, swine, egg and poultry. All feed (100%) for farm products is considered to have been grown on contaminated portions of the site. For these farm products, risks are provided for the farm product itself (produce, beef, milk, etc.). Also like the resident, age-adjusted intake equations were developed for all of the consumption equations to account for changes in intake as the receptor ages.

Graphical Representation

Agricultural Biota, Soil and Water Graphic and Supporting Text

Equations

consumption of produce. The exposed and root vegetable consumption rates were combined to represent total vegetable consumption. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11.

consumption of poultry. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of eggs. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of beef. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of milk. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. No adjustment for losses U.S. EPA 1998. Home produced dairy total was converted to fluid milk by a factor of 82% (82% of total dairy consumed is fluid milk. )

consumption of swine. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of fish. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss as was done in U.S. EPA 1998.

4.8.2 Farmer Direct Exposure and Consumption of Agricultural Products - Back Calculated to Soil

The farmer scenario should be considered an extension of the resident scenario and evaluate consumption of farm products for a subsistence farmer. Like the resident, the farmer scenario assumes the receptor will be exposed via the following pathways: incidental ingestion of soil, external radiation from contaminants in soil, inhalation of fugitive dust and consumption of home grown produce (100% of fruit and vegetables are from the farm). In addition to produce, 100% of consumption of the following are also considered to be from the farm: beef, milk, fish, swine, egg and poultry. All feed (100%) for farm products is considered to have been grown on contaminated portions of the site. For these farm products, risks are provided for soil which may contribute contaminants to the products. Also like the resident, age-adjusted intake equations were developed for all of the ingestion/consumption equations to account for changes in intake as the receptor ages.

Graphical Representation

Equations

incidental ingestion of soil,

inhalation of particulates emitted from soil,

external exposure to ionizing radiation, and

consumption of produce. The exposed and root vegetable consumption rates were combined to represent total vegetable consumption. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11.

consumption of eggs. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of poultry. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of fish. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss as was done in U.S. EPA 1998.

consumption of beef. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of milk. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. No adjustment for losses U.S. EPA 1998. Home produced dairy total was converted to fluid milk by a factor of 82% (82% of total dairy consumed is fluid milk. )

consumption of swine. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

4.8.3 Farmer Direct Exposure and Consumption of Agricultural Products - Back Calculated to Water

The farmer scenario should be considered an extension of the resident scenario and evaluate consumption of farm products for a subsistence farmer. Like the resident, the farmer scenario assumes the receptor will be exposed via the following pathways: ingestion of tap water, external radiation from contaminants in tap water, inhalation of gases in tap water and consumption of home grown produce (100% of fruit and vegetables are from the farm). The inhalation exposure route is only calculated for C-14, H-3, Rn-220, and Rn-222 which volatilize. The submersion route is also included for radioactive gases in tapwater. This addition was based on research found in ORNL/TM-2023/3001 - Quantifying the Impact of the Exclusion of the Submersion Exposure Route in Soil and Tap Water Models in Existing Superfund Radionuclide Screening Level Calculators. In addition to produce, 100% of consumption of the following are also considered to be from the farm: beef, milk, fish, swine, egg and poultry. All water (100%) for farm products is considered to have been provided from contaminated portions of the site. For these farm products, risks are provided for the water which may contribute contaminants to the products. Also like the resident, age-adjusted intake equations were developed for all of the ingestion/consumption equations to account for changes in intake as the receptor ages.

Graphical Representation

Equations

ingestion of tap water,

inhalation, (The inhalation exposure route is only calculated for C-14, H-3, Rn-220, Rn-222, and Rn-222+D). Also, volatilization in the equation comes from household uses of water (e.g., showering, laundering, dish washing)

submersion, (The submersion exposure route is only calculated for C-14, H-3, Rn-220, Rn-222, and Rn-222+D). Also, volatilization in the equation comes from household uses of water (e.g., showering, laundering, dish washing)

immersion in water

consumption of produce. The exposed and root vegetable consumption rates were combined to represent total vegetable consumption. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11.

consumption of eggs. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of poultry. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of fish. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss as was done in U.S. EPA 1998.

consumption of beef. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

consumption of milk. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. No adjustment for losses U.S. EPA 1998. Home produced dairy total was converted to fluid milk by a factor of 82% (82% of total dairy consumed is fluid milk. )

consumption of swine. Intake rates from the Exposure Factors Handbook were averaged over age groups to determine adult and child intake rates. Where no intake rate was given for an age group, the mean value was substituted and the intake rate from the 6 to 11 age group was assumed to be the same for ages 7 to 11. There was no adjustment for preparation or cooking loss U.S. EPA 1998.

4.9 Soil to Groundwater

The soil migration to groundwater risk scenario is used to determine risk from groundwater exposure based on concentration in soil. Migration of contaminants from soil to groundwater can be envisioned as a two-stage process: (1) release of contaminant from soil to soil leachate and (2) transport of the contaminant through the underlying soil and aquifer to a receptor well. The soil to groundwater scenario considers both of these fate and transport mechanisms. The groundwater concentration is determined using a known concentration in soil, radionuclide specific Kd, and a dilution attenuation factor to obtain a risk. The soil to groundwater media option is included in both resident and indoor worker land use scenarios as they both model tap water risk.

Resident Graphical Representation

Indoor Worker Graphical Representation

Equations

The user has the option to choose from two calculation methods. The first method employs the default partitioning equation for migration to groundwater. The dilution attenuation factor defaults to 20 for a 0.5-acre source. If the user has all of the parameters needed to calculate a dilution attenuation factor, you may use the Method 2 (mass-limit equation for migration to groundwater). The groundwater concentration, determined with either of these equations, is used to calculate the tap water chronic daily intake equations presented in secion 4.1.4.

Method 1. Partitioning Equation for Migration to Groundwater

Method 2. Mass-Limit Equation for Migration to Groundwater

4.9.1 Determination of the Dilution Attenuation Factor

The default risk/hazard values are based on a dilution attenuation factor of 1. If one wishes to use the calculator to calculate risks or hazards using the SSL guidance for a source up to 0.5 acres, then a dilution attenuation factor of 20 can be used. If all of the parameters needed to calculate a site-specific dilution attenuation factor are known, they may be entered.

DAF Graphical Representation

dilution attenuation factor.

4.10 Supporting Equations and Parameter Discussion

There are three parts of the above land use equations that require further explanation. The first is explanation of two inhalation variables: the particulate emission factor (PEF) and the volatilization factor (VF). The second is the use of the radionuclide decay constant (λ). The third is the explanation of the area correction factor (ACF).

4.10.1 Particulate Emission Factor (PEF) and Volatilization Factor (VF)

Inhalation of isotopes adsorbed to respirable particles (PM10) was assessed using a default PEF equal to 1.36 x 109 m³/kg. This equation relates the contaminant concentration in soil with the concentration of respirable particles in the air due to fugitive dust emissions from contaminated soils. The generic PEF was derived using default values that correspond to a receptor point concentration of approximately 0.76 µg/m³. The relationship is derived by Cowherd (1985) for a rapid assessment procedure applicable to a typical hazardous waste site, where the surface contamination provides a relatively continuous and constant potential for emission over an extended period of time (e.g. years). This represents an annual average emission rate based on wind erosion that should be compared with chronic health criteria; it is not appropriate for evaluating the potential for more acute exposures. Definitions of the input variables are in Section 5.

With the exception of specific heavy metals, the PEF does not appear to significantly affect most soil screening levels. The equation forms the basis for deriving a generic PEF for the inhalation pathway. For more details regarding specific parameters used in the PEF model, refer to Soil Screening Guidance: Technical Background Document. The use of alternate values on a specific site should be justified and presented in an Administrative Record if considered in CERCLA remedy selection.

Note: the generic PEF evaluates wind-borne emissions and does not consider dust emissions from traffic or other forms of mechanical disturbance that could lead to greater emissions than assumed here.

EPA derived a default volatilization factor (VF) value of 17 m³/kg for tritium. The VF replaces the PEF in the risk equations when tritium is being addressed. This VF value is based on a steady-state model that assumes, on average, tritium in soil pore water and tritium in air (as tritiated water vapor) will be distributed in the environment in proportion to the average water content in soil and air. EPA assumes a mean atmospheric humidity of 6 grams of water per cubic meter of air (g/m³) nationwide (Etnier 1980) and an average soil moisture content of 10% (i.e., 100 grams of water per kilogram of soil). Given these assumptions, EPA calculates the VF term for tritium as

VFH-3 = 100 g H2O/kg soil ÷ 6 g H2O/m³ air

= 17 m³ air/kg soil

= 17 m³/kg

EPA believes that this value is appropriate for the average case, both outdoors and indoors. However, site managers can derive a site-specific VF term for tritium that may be more appropriate for a specific site, considering local atmospheric humidity and soil moisture content.

4.10.2 Unpaved Road Vehicle Traffic Particulate Emission Factor (PEF_sc)

The equation to calculate the subchronic particulate emission factor (PEF_sc) is significantly different from the residential and non-residential PEF equations. The PEF_sc focuses exclusively on emissions from truck traffic on unpaved roads, which typically contribute the majority of dust emissions during construction. This equation requires estimates of parameters such as the number of days with at least 0.01 inches of rainfall, the mean vehicle weight, and the sum of fleet vehicle distance traveled during construction.

The number of days with at least 0.01 inches of rainfall can be estimated using Exhibit 5-2 in the supplemental soil screening guidance. Mean vehicle weight (W) can be estimated by assuming the numbers and weights of different types of vehicles. For example, assuming that the daily unpaved road traffic consists of 20 two-ton cars and 10 twenty-ton trucks, the mean vehicle weight would be:

W = [(20 cars x 2 tons/car) + (10 trucks x 20 tons/truck)]/30 vehicles = 8 tons

The sum of the fleet vehicle kilometers traveled during construction (∑ VKT) can be estimated based on the size of the area of surface soil contamination, assuming the configuration of the unpaved road, and the amount of vehicle traffic on the road. For example, if the area of surface soil contamination is 0.5 acres (or 2,024 m²) and one assumes that this area is configured as a square with the unpaved road segment dividing the square evenly, the road length would be equal to the square root of 2,024 m², 45 m (or 0.045 km). Assuming that each vehicle travels the length of the road once per day, 5 days per week for a total of 6 months, the total fleet vehicle kilometers traveled would be:

∑ VKT = 30 vehicles x 0.045 km/day x (52 wks/yr / 2) x 5 days/wk = 175.5 km

4.10.3 Other Than Unpaved Road Vehicle Traffic Particulate Emission Factor (PEF'_sc)

Other than emissions from unpaved road traffic, the construction worker may also be exposed to particulate matter emissions from wind erosion, excavation soil dumping, dozing, grading, and tilling or similar operations PEF'_sc. These operations may occur separately or concurrently and the duration of each operation may be different. For these reasons, the total unit mass emitted from each operation is calculated separately and the sum is normalized over the entire area of contamination and over the entire time during which construction activities take place. Equation E-26 in the supplemental soil screening guidance was used.

4.10.4 Radionuclide Decay Constant (λ)

The decay constant term (λ), which is based on the half-life of the isotope, is used for some media in nearly all land uses. λ = 0.693/half-life in years (where, 0.693=ln(2)). The term (1 - e^-λt) takes into account the number of half-lives that will occur within the exposure duration to calculate an appropriate value. The intention of the +D term is to generate realistic risks by including the contributions from their short-lived decay products, assuming equal activity concentrations (i.e. , secular equilibrium) with the principal or parent nuclide in the environment. (Note that there is one exception to the assumption of secular equilibrium. For the inhalation slope factor for Rn-222+D reported in the table, EPA assumes a 50% equilibrium value for radon decay products (Po-218, Pb-214, Bi-214and Po-214) in air. ) In most cases, site-specific analytical data should be used to establish the actual degree of equilibrium between each parent radionuclide and its decay products in each media sampled. However, in the absence of empirical data, the "+D" values for radionuclides should be used unless there are compelling reasons not to do so. Definitions of the input variables are in Section 5.

4.10.5 Area Correction Factor

The RAGS/HHEM Part B model assumes that an individual is exposed to a source geometry that is effectively an infinite slab. The concept of an infinite slab means that the thickness of the contaminated zone and its aerial extent are so large that it behaves as if it were infinite in its physical dimensions. In practice, soil contaminated to a depth greater than about 15 cm and with an aerial extent greater than about 1,000 m² will create a radiation field comparable to that of an infinite slab. (U.S. EPA. 2000a)

To accommodate the fact that in most residential settings the assumption of an infinite slab source will result in overly conservative SSLs, an adjustment for source area is considered to be an important modification to the RAGS/HHEM Part B model. Thus, an area correction factor, ACF, has been added to the calculation of SSLs. (U.S. EPA. 2000a)

For further description of the ACF, follow the link here.

4.10.6 Gamma Shielding Factor

CDIs in this guidance are calculated without any shielding between them and the source (soil). In this case, a default soil gamma shielding factor for outdoor exposure to ionizing radiation (GSF_o is established at 1.0 (0% shielding). It is common to have some shielding (soil cover) over contaminated soil. When the calculator is ran in site-specific mode the user must select a soil cover depth. Due to shielding, covering the contaminated area with soil will produce lower dose and risk coefficients that are stated in the Federal Guidance Report (FGR) 12 and 13. Therefore, gamma shielding factors are needed to apply the published EPA risk values to the buried contamination scenarios. Outdoor gamma shielding factors (GSF_o) are derived by modeling various thicknesses of clean soil covering ground soil contamination. The gamma shielding factor is defined as the ratio of the dose corresponding to covered contamination to that of an unshielded surface source in soil. The MCNP output was used to derive kerma values one meter above the soil surface for various scenarios ranging from 0 cm soil cover to 100 cm soil cover in 10 cm increments while using source thicknesses of ground plane, 1, 5 and 15 cm source volumes as well as infinite source volume. Radioisotopes published in ICRP 107 were considered, along with decay chains of several radioisotopes. The Center for Radiation Protection Knowledge has provided GSF_o values here and an appendix containing +D and +E values.

A default gamma shielding factor for indoor exposure to ionizing radiation (GSF_i is established at 0.4 (60% shielding)

A default gamma shielding factor for exposure to ionizing radiation in air (GSF_a is established at 1 (0% shielding)

4.10.7 Mass Loading Factor (MLF) Conversion

4.10.8 Modeling Parameters for Animals and Animal Products

Pasture Mass Loading Factor (MLF_pasture)

The plant mass loading factor is defined as the ratio of the mass of soil on vegetation per mass of dry vegetation (Hinton, 1992). The mass loading factor is strictly the amount of soil that is resuspended and then remains on the plant which differs from incidental ingestion of soil by an animal.

Transfer Factor (TF)

The ratio of contaminant concentration in animal tissue (mg contaminant/kg tissue, wet weight) to daily intake (mg contaminant/day) is defined as the biotransfer factor (TF). It is a measure of how much of what the animal ingests is actually transferred to tissue. The TF (day/kg) is multiplied by a species-specific fodder ingestion rate (kg/day) and by the contaminant concentration in food (Rupp + Res) to obtain an estimate of the concentration in meat (mg contaminant/kg tissue). TFs are radionuclide- and species-specific.

Fodder Intake Rate (Q_p)

Animal fodder intake rates are sometimes reported as wet weight and sometimes as dry weight. Since the soil to plant transfer factors (BV) for plants are reported on a dry weight basis, daily food intake rates should also be in dry weight.

Soil Intake Rate (Q_s)

Soil ingestion by animals can be a significant exposure route. Animals may ingestion soil incidentally during grazing, grooming activities, or deliberately in search of minerals.

Water Intake Rate (Q_w)

Animal water ingestion rates vary by species, dry matter intake, body size, productivity, and environmental condition.

Fraction of Time Animal is On-Site (f_p)

This parameter accounts for the period of time which an animal is likely to be exposed to contaminants on the site. For livestock, this is the time on pasture. In some geographic regions, animals are only on pasture for a portion of the year. Site-specific values are desirable as grazing practices vary considerably with geographic region.

Fraction of Animal's Food from Site when On-Site (f_s)

Supplemental feeding of livestock on pasture is a common management practice, therefore, a parameter to account for the fraction of an animal's daily food ingestion that comes from a site has been included in the exposure model.

Fraction of Animal's Water from Site when On-Site (f_w)

The fraction of an animal’s daily water intake that is obtained from water at a site. Generally, animals are assumed to obtain 100% of their water from the site unless site conditions or management practices are known to influence access to site-related water.

The tables below present the definitions of the variables and their default values. This calculator follows the recommendations in the OSWER Directive concerning use of exposure parameters from the 2011 Exposure Factors Handbook. Any alternative values or assumptions used in remedy evaluation or selection on a CERCLA site should be presented with supporting rationale in Administrative Records.

Table 1. Slope Factors (SFs)

Symbol	Definition (units)	Default	Reference
SFs	Soil Ingestion Slope Factor - population (risk/pCi)	Isotope-specific	ORNL 2014c
SFsa	Soil Ingestion Slope Factor - adult only (risk/pCi)	Isotope-specific	ORNL 2014c
SFf	Food Ingestion Slope Factor (risk/pCi)	Isotope-specific	ORNL 2014c
SFw	Water Ingestion Slope Factor (risk/pCi)	Isotope-specific	ORNL 2014c
SFi	Slope Factor - inhalation (risk/pCi)	Isotope-specific	ORNL 2014c
SFext-sv	Slope Factor - external exposure (risk/yr per pCi/g)	Isotope-specific	ORNL 2014c
SFext-sv1	Slope Factor - external exposure (risk/yr per pCi/g)	Isotope-specific	ORNL 2014c
SFext-sv5	Slope Factor - external exposure (risk/yr per pCi/g)	Isotope-specific	ORNL 2014c
SFext-sv15	Slope Factor - external exposure (risk/yr per pCi/g)	Isotope-specific	ORNL 2014c
SFext-gp	Slope Factor - external exposure (risk/yr per pCi/cm2)	Isotope-specific	ORNL 2014c
SFsub	Slope Factor - submersion (risk/yr per pCi/cm3)	Isotope-specific	ORNL 2014c
SFimm	Slope Factor - immersion (risk/yr per pCi/L)	Isotope-specific	ORNL 2014c

Table 2. Miscellaneous Variables

Symbol	Definition (units)	Default	Reference
Csoil	Concentration of contaminant in soil (pCi/g)	User-input
Cg-water	concentration of contaminant in groundwater (pCi/L)	User-input
Cs-water	concentration of contaminant in surface water (pCi/L)	User-input
Cair	concentration of contaminant in air (pCi/m3)	User-input
Cfish	concentration of contaminant in fish (pCi/g)	User-input
Cproduce	concentration of contaminant in produce (pCi/g)	User-input
Cmilk	concentration of contaminant in milk (pCi/g)	User-input
Cbeef	concentration of contaminant in beef (pCi/g)	User-input
Cpoultry	Concentration of contaminant in poultry (pCi/g)	User-input
Cegg	Concentration of contaminant in egg (pCi/g)	User-input
Cswine	Concentration of contaminant in swine (pCi/g)	User-input
Cgame	Concentration of contaminant in game (pCi/g)	User-input
Cfowl	Concentration of contaminant in fowl (pCi/g)	User-input
λ	decay constant = 0.693/half-life (year-1) where 0.693 = ln(2)	Isotope-specific	Developed for Radionuclide Soil Screening calculator
K	Andelman Volatilization Factor (L/m3)	0.5	U.S. EPA 1991b (pg. 20)
ACFext-sv	Area Correction Factor - soil volume (unitless)	Isotope-specific	ORNL 2014a
ACFext-sv1	Area Correction Factor - sv1 (unitless)	Isotope-specific	ORNL 2014a
ACFext-sv5	Area Correction Factor - sv5 (unitless)	Isotope-specific	ORNL 2014a
ACFext-sv15	Area Correction Factor - sv15 (unitless)	Isotope-specific	ORNL 2014a
ACFext-gp	Area Correction Factor - ground plane (unitless)	Isotope-specific	ORNL 2014a
GSFi	Gamma Shielding Factor - Indoor (unitless)	0.4	U.S. EPA 2000a. (pg. 2-22). U.S. EPA 2000b. (pg. 2-18)
GSFext-sv	Gamma Shielding Factor - soil volume (unitless)	Isotope-specific	ORNL 2014a
GSFext-sv1	Gamma Shielding Factor - sv1 (unitless)	Isotope-specific	ORNL 2014b
GSFext-sv5	Gamma Shielding Factor - sv5 (unitless)	Isotope-specific	ORNL 2014b
GSFext-sv15	Gamma Shielding Factor - sv15 (unitless)	Isotope-specific	ORNL 2014b
GSFext-gp	Gamma Shielding Factor - ground plane (unitless)	Isotope-specific	ORNL 2014b
GSFa	Gamma Shielding Factor - Air (unitless)	1	Developed for Radionuclide Soil Screening calculator

Table 3. Resident Soil

Symbol	Definition (units)	Default	Reference
CDIres-sol-ing	Resident Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIres-sol-inh	Resident Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIres-sol-ext	Resident Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIres-sol-sv	Resident Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIres-sol-sv1	Resident Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIres-sol-sv5	Resident Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIres-sol-sv15	Resident Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIres-sol-gp	Resident Soil Radionuclide External (pCi-year/cm2)	Contaminant-specific	Determined in this calculator
tres	Time - resident (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
CFres-produce	Produce Contaminated Fraction - resident (unitless)	0.25	U.S. EPA 1990. U.S. EPA. 1998. (pg. C-9)
Bvwet	Soil to Plant Transfer Factor - wet (pCi/g-fresh plant per pCi/g-dry soil)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Rupv	Wet root uptake for produce multiplier (unitless)	Radionuclide-specific (=Bvwet)	Hierarchy selection in Section 2.3.2
Res	Soil resuspension multiplier (dimensionless)	=MLF (pasture or produce)	Hinton 1992
IFSres-adj	Resident Ingestion Fraction - age-adjusted (mg)	1,120,000	Calculated using the age-adjusted intake factors equation.
IRSres-a	Resident Soil Ingestion Rate - adult (mg/day)	100	U.S. EPA 1991a (pg. 15)
IRSres-c	Resident Soil Ingestion Rate - child (mg/day)	200	U.S. EPA 1991a (pg. 15)
IFAres-adj	Resident Inhalation Rate - age-adjusted (m3)	161,100	Calculated using the age-adjusted intake factors equation.
IRAres-a	Resident Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRAres-c	Resident Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
IFVres-adj	Resident Vegetable Ingestion Fraction - age-adjusted (g)	989,870	Calculated using the age-adjusted intake factors equation
IRVres-a	Resident Vegetable Ingestion Rate - adult (g/day)	128.9	U.S. EPA 2011 (Table 13-10)
IRVres-c	Resident Vegetable Ingestion Rate - child (g/day)	41.7	U.S. EPA 2011 (Table 13-10)
IFFres-adj	Resident Fruit Ingestion Fraction - age-adjusted (g)	1,462,510	Calculated using the age-adjusted intake factors equation
IRFres-a	Resident Fruit Ingestion Rate - adult (g/day)	188.5	U.S. EPA 2011 (Table 13-5)
IRFres-c	Resident Fruit Ingestion Rate - child (g/day)	68.1	U.S. EPA 2011 (Table 13-5)
EFres	Resident Exposure Frequency - (days/year)	350	U.S. EPA 1991a (pg. 15)
EFres-a	Resident Exposure Frequency - adult (days/year)	350	U.S. EPA 1991a (pg. 15)
EFres-c	Resident Exposure Frequency - child (days/year)	350	U.S. EPA 1991a (pg. 15)
EDres	Resident Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
EDres-a	Resident Exposure Duration - adult (years)	20	EDres (26 years) - EDres-c (6 years)
EDres-c	Resident Exposure Duration - child (years)	6	U.S. EPA 1991a, Pages 6 and 15
ETres	Resident Exposure Time (hours/day)	24	24 Hours per 24 hour Day
ETres-a	Resident Exposure Time - adult (hours/day)	24	24 Hours per 24 hour Day
ETres-c	Resident Exposure Time - child (hours/day)	24	24 Hours per 24 hour Day
ETres-i	Resident Exposure Time - indoor (hours/day)	16.416	U.S. EPA 2011 (Table 16-16 50th%)
ETres-o	Resident Exposure Time - outdoor (hours/day)	1.752	U.S. EPA 2011 (Table 16-20 50th%))

Table 4. Indoor Worker Soil

Symbol	Definition (units)	Default	Reference
CDIind-sol-ing	Indoor Worker Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIind-sol-inh	Indoor Worker Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIind-sol-ext	Indoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIind-sol-sv	Indoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIind-sol-sv1	Indoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIind-sol-sv5	Indoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIind-sol-sv15	Indoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIind-sol-gp	Indoor Worker Soil Radionuclide External (pCi-year/cm2)	Contaminant-specific	Determined in this calculator
tind	Time - indoor worker (years)	25	U.S. EPA 1991a (pg. 15)
IRSind	Indoor Worker Soil Ingestion Rate (mg/day)	50	U.S. EPA 2001 (pg. 4-3)
IRAind	Indoor Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFind	Indoor Worker Exposure Frequency (days/year)	250	U.S. EPA 1991a (pg. 15)
EDind	Indoor Worker Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETind	Indoor Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 5. Outdoor Worker Soil

Symbol	Definition (units)	Default	Reference
CDIout-sol-ing	Outdoor Worker Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIout-sol-inh	Outdoor Worker Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIout-sol-ext	Outdoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIout-sol-sv	Outdoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIout-sol-sv1	Outdoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIout-sol-sv5	Outdoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIout-sol-sv15	Outdoor Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIout-sol-gp	Outdoor Worker Soil Radionuclide External (pCi-year/cm2)	Contaminant-specific	Determined in this calculator
tout	Time - outdoor worker (years)	25	U.S. EPA 1991a (pg. 15)
IRSout	Outdoor Worker Soil Ingestion Rate (mg/day)	100	U.S. EPA 1991a (pg. 15)
IRAout	Outdoor Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFout	Outdoor Worker Exposure Frequency (days/year)	225	U.S. EPA 1991a (pg. 15)
EDout	Outdoor Worker Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETout	Outdoor Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 6. Composite Worker Soil

Symbol	Definition (units)	Default	Reference
CDIcom-sol-ing	Composite Worker Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIcom-sol-inh	Composite Worker Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIcom-sol-ext	Composite Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcom-sol-sv	Composite Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcom-sol-sv1	Composite Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcom-sol-sv5	Composite Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcom-sol-sv15	Composite Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcom-sol-gp	Composite Worker Soil Radionuclide External (pCi-year/cm2)	Contaminant-specific	Determined in this calculator
tcom	Time - worker (years)	25	U.S. EPA 1991a (pg. 15)
IRScom	Composite Worker Soil Ingestion Rate (mg/day)	100	U.S. EPA 1991a (pg. 15)
IRAcom	Composite Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFcom	Composite Worker Exposure Frequency (days/year)	250	U.S. EPA 1991a (pg. 15)
EDcom	Composite Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETcom	Composite Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 7. Excavation Worker Soil

Symbol	Definition (units)	Default	Reference
CDIexc-sol-ing	Excavation Worker Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIexc-sol-inh	Excavation Worker Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIexc-sol-ext	Excavation Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
texc	Time - excavation worker (years)	1	U.S. EPA 2002 Exhibit 5-1
IRSexc	Excavation Worker Soil Ingestion Rate (mg/day)	330	U.S. EPA 2002 (Exhibit 1-2)
IRAexc	Excavation Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFexc	Excavation Worker Exposure Frequency (days/year)	20	Based on 5 days per week for 4 weeks
EDexc	Excavation Worker Exposure Duration (years)	1	U.S. EPA 2002 Exhibit 5-1
ETexc-o	Excavation Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 8. Construction Worker Soil

Symbol	Definition (units)	Default	Reference
CDIcon-sol-ing	Construction Worker Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIcon-sol-inh	Construction Worker Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIcon-sol-ext	Construction Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcon-sol-sv	Construction Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcon-sol-sv1	Construction Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcon-sol-sv5	Construction Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcon-sol-sv15	Construction Worker Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIcon-sol-gp	Construction Worker Soil Radionuclide External (pCi-year/cm2)	Contaminant-specific	Determined in this calculator
tcon	Time - construction worker (years)	1	U.S. EPA 2002 Exhibit 5-1
IRScon	Construction Worker Soil Ingestion Rate (mg/day)	330	U.S. EPA 2002 (Exhibit 1-2)
IRAcon	Construction Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFcon	Construction Worker Exposure Frequency (days/year)	250	U.S. EPA 2002 Exhibit 5-1
EWcon	Construction Worker Exposure Frequency (weeks/year)	50	U.S. EPA 2002 Exhibit 5-1
DWcon	Construction Worker Exposure Frequency (days/week)	5	U.S. EPA 2002 Exhibit 5-1
EDcon	Construction Worker Exposure Duration (years)	1	U.S. EPA 2002 Exhibit 5-1
ETcon	Construction Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 9. Recreator Soil/Sediment

Symbol	Definition (units)	Default	Reference
CDIrec-sol-ing	Recreator Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIrec-sol-inh	Recreator Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIrec-sol-ext	Recreator Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIrec-sol-sv	Recreator Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIrec-sol-sv1	Recreator Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIrec-sol-sv5	Recreator Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIrec-sol-sv15	Recreator Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIrec-sol-gp	Recreator Soil Radionuclide External (pCi-year/cm2)	Contaminant-specific	Determined in this calculator
CDIrec-sol-fowl-ing	Recreator Fowl Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIrec-sol-game-ing	Recreator Game Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
trec	Time - recreator (years)	Site-specific	Site-specific
IFSrec-adj	Recreator Ingestion Fraction - age-adjusted (mg)	240,000	Calculated using the age-adjusted intake factors equation.
IRSrec-a	Recreator Soil Ingestion Rate - adult (mg/day)	100	U.S. EPA 1991a (pg. 15)
IRSrec-c	Recreator Soil Ingestion Rate - child (mg/day)	200	U.S. EPA 1991a (pg. 15)
IFArec-adj	Recreator Inhalation Fraction - age-adjusted (m3)	1,437.5	Calculated using the age-adjusted intake factors equation.
IRArec-a	Recreator Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRArec-c	Recreator Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
EFrec	Recreator Exposure Frequency - (days/year)	75	reasonable estimate. See 4.7.1
EFrec-a	Recreator Exposure Frequency - adult (days/year)	75	reasonable estimate. See 4.7.1
EFrec-c	Recreator Exposure Frequency - child (days/year)	75	reasonable estimate. See 4.7.1
EDrec	Recreator Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
EDrec-a	Recreator Exposure Duration - adult (years)	20	EDres (26 years) - EDres-c (6 years)
EDrec-c	Recreator Exposure Duration - child (years)	6	U.S. EPA 1991a, Pages 6 and 15
ETrec	Recreator Exposure Time (hours/day)	1	reasonable estimate. See 4.7.1
ETrec-a	Recreator Exposure Time - adult (hours/day)	1	reasonable estimate. See 4.7.1
ETrec-c	Recreator Exposure Time - child (hours/day)	1	reasonable estimate. See 4.7.1
IRGLrec-game	Recreator Land Game Ingestion Rate (g/day)	Site-specific	Site-specific
IRGFrec-fowl	Recreator Fowl Ingestion Rate (g/day)	Site-specific	Site-specific
CFrec-game	Game Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFrec-fowl	Fowl Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
Bvdry	Soil to Plant Transfer Factor - dry (pCi/g-dry plant per pCi/g-dry soil)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Rupp	Dry root uptake for pasture multiplier (dimensionless)	Radionuclide-specific (=Bvdry)	Hierarchy selection in Section 2.3.2
TFbeef	Game Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFpoultry	Fowl Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Qp-game	Game Fodder Intake Rate (kg/day)	Site-specific	Site-specific
Qp-fowl	Fowl Fodder Intake Rate (kg/day)	Site-specific	Site-specific
Qs-game	Game Soil Intake Rate (kg/day)	Site-specific	Site-specific
Qs-fowl	Fowl Soil Intake Rate (kg/day)	Site-specific	Site-specific
fp-game	Fraction of Time Animal is On-Site - game (unitless)	1	Assumes 100%
fp-fowl	Fraction of Time Animal is On-Site - fowl (unitless)	1	Assumes 100%
fs-game	Fraction of Animal's Food from Site when On-Site - game (unitless)	1	Assumes 100%
fs-fowl	Fraction of Animal's Food from Site when On-Site - fowl (unitless)	1	Assumes 100%

Table 10. Farmer Soil

Symbol	Definition (units)	Default	Reference
CDIfar-sol-ing	Farmer Soil Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-inh	Farmer Soil Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-ext	Farmer Soil Radionuclide External (pCi-year/g)	Contaminant-specific	Determined in this calculator
CDIfar-sol-produce-ing	Farmer Produce Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-poultry-ing	Farmer Poultry Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-egg-ing	Farmer Egg Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-beef-ing	Farmer Beef Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-dairy-ing	Farmer Dairy Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-swine-ing	Farmer Swine Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-sol-fsh-ing	Farmer Fish Radionuclide Back-calculated Concentration in Soil Ingestion (pCi)	Contaminant-specific	Determined in this calculator
ρm	Density of milk (kg/L)	1.03	Milk Composition & Synthesis Resource Library
tfar	Time - farmer (years)	40	U.S. EPA 2005 (pg. C-24/C-26)
Bvwet	Soil to Plant Transfer Factor - wet (pCi/g-fresh plant per pCi/g-dry soil)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Bvdry	Soil to Plant Transfer Factor - dry (pCi/g-dry plant per pCi/g-dry soil)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Rupv	Dry root uptake for produce multiplier (unitless)	Radionuclide-specific (=Bvwet)	Hierarchy selection in Section 2.3.2
Rupp	Dry root uptake for pasture multiplier (dimensionless)	Radionuclide-specific (=Bvdry)	Hierarchy selection in Section 2.3.2
Res	Soil resuspension multiplier (dimensionless)	=MLF (pasture or produce)	Hinton 1992
TFbeef	Beef Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFdairy	Dairy Transfer Factor (day/L)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFswine	Swine Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFpoultry	Poultry Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFegg	Egg Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
MLFproduce	Produce Plant Mass Loading Factor (unitless)	0.26 x 0.052 = 0.0135	Hinton, 1992. U.S. EPA SSG 1996 table G-1. Dry weight to wet weight conversion equation from section 4.10.7.
MLFpasture	Pasture Plant Mass Loading Factor (unitless)	0.25	Hinton, T. G. 1992
Qp-beef	Beef Fodder Intake Rate (kg/day)	11.77	U.S. EPA 2005 (pg. B-138)
Qp-dairy	Dairy Fodder Intake Rate (kg/day)	20.3	U.S. EPA 2005 (pg. B-145)
Qp-swine	Swine Fodder Intake Rate (kg/day)	4.7	U.S. EPA 2005 (pg. B-152)
Qp-poultry	Poultry Fodder Intake Rate (kg/day)	0.2	U.S. EPA 2005 (pg. B-158/164)
Qs-beef	Beef Soil Intake Rate (kg/day)	0.5	U.S. EPA 2005 (pg. B-139)
Qs-dairy	Dairy Soil Intake Rate (kg/day)	0.4	U.S. EPA 2005 (pg. B-146)
Qs-swine	Swine Soil Intake Rate (kg/day)	0.37	U.S. EPA 2005 (pg. B-153)
Qs-poultry	Poultry Soil Intake Rate (kg/day)	0.022	U.S. EPA 2005 (pg. B-159/165)
fp-beef	Fraction of Time Animal is On-Site - beef (unitless)	1	Developed for this calculator
fp-dairy	Fraction of Time Animal is On-Site - dairy (unitless)	1	Developed for this calculator
fp-swine	Fraction of Time Animal is On-Site - swine (unitless)	1	Developed for this calculator
fp-poultry	Fraction of Time Animal is On-Site - poultry (unitless)	1	Developed for this calculator
fs-beef	Fraction of Animal's Food from Site when On-Site - beef (unitless)	1	Developed for this calculator
fs-dairy	Fraction of Animal's Food from Site when On-Site - dairy (unitless)	1	Developed for this calculator
fs-swine	Fraction of Animal's Food from Site when On-Site - swine (unitless)	1	Developed for this calculator
fs-poultry	Fraction of Animal's Food from Site when On-Site - poultry (unitless)	1	Developed for this calculator
IFSfar-adj	Farmer Soil Ingestion Fraction - age-adjusted (mg)	1,610,000	Calculated using the age-adjusted intake factors equation.
IRSfar-a	Farmer Soil Ingestion Rate - adult (mg/day)	100	U.S. EPA 1991a (pg. 15)
IFAfar-adj	Farmer Inhalation Rate - age-adjusted (m3)	259,000	Calculated using the age-adjusted intake factors equation.
IRAfar-a	Farmer Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRAfar-c	Farmer Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
IRSfar-c	Farmer Soil Ingestion Rate - child (mg/day)	200	U.S. EPA 1991a (pg. 15)
EFfar	Farmer Exposure Frequency (days/year)	350	U.S. EPA 1991a (pg. 15)
EFfar-a	Farmer Exposure Frequency - adult (days/year)	350	U.S. EPA 1991a (pg. 15)
EFfar	Farmer Exposure Frequency - child (days/year)	350	U.S. EPA 1991a (pg. 15)
EDfar	Farmer Exposure Duration (years)	40	U.S. EPA 2005 (Table 6-3)
EDfar-a	Farmer Exposure Duration - adult (years)	34	U.S. EPA 1994a
EDfar-c	Farmer Exposure Duration - child (years)	6	U.S. EPA 2005 (Table 6-3)
ETfar	Farmer Exposure Time - (hours/day)	24	24 Hours per 24 hour Day
ETfar-a	Farmer Exposure Time - Adult (hours/day)	24	24 Hours per 24 hour Day
ETfar-c	Farmer Exposure Time - Child (hours/day)	24	24 Hours per 24 hour Day
ETfar-i	Farmer Exposure Time - indoor (hours/day)	10.008	1440 hrs/day - (ETfar-o + ETfar-a)
ETfar-away	Farmer Exposure Time - away (hours/day)	1.83	U.S. EPA 2011 (Tables 16-20 and 16-24 total of time in vehicles, near vehicles and outdoors other than near residence 25th%)
ETfar-o	Farmer Exposure Time - outdoor (hours/day)	12.168	U.S. EPA 2011 (Table 16-20 95th%))

Table 11. Resident Tap Water

Symbol	Definition (units)	Default	Reference
CDIres-wat-ing	Resident Tap Water (Groundwater) Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIres-wat-sub	Resident Tap Water (Groundwater) Radionuclide Submersion (pCi)	Contaminant-specific	Determined in this calculator
CDIres-wat-inh	Resident Tap Water (Groundwater) Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIres-wat-imm	Resident Tap Water (Groundwater) Radionuclide Immersion (pCi-year/L)	Contaminant-specific	Determined in this calculator
Irrrup	root uptake from irrigation multiplier (L/kg)	Isotope-specific	Calculated
Irrres	resuspension from irrigation multiplier (L/kg)	Isotope-specific	Calculated
Irrdep	aerial deposition from irrigation multiplier (L/kg)	Isotope-specific	Calculated
Bvwet	Soil to Plant Transfer Factor - wet (pCi/g-fresh plant per pCi/g-dry soil)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
F	Irrigation Period (unitless)	0.25	Personal communication
If	Interception Fraction (unitless)	0.42	Miller, C. W. 1980
Ir	Irrigation Rate (L/m2)	3.62	Personal communication
λHL	Soil Leaching Rate (1/day)	0.000027	NCRP 1996
λi	decay (1/day)	0.693/TR - radionuclides	NCRP 1996
λE	Decay for Removal on Produce (1/day)	λi + (0.693/tw)	NCRP 1996
λB	Effective Rate for Removal (1/day)	λHL - λi	NCRP 1996
T	Translocation Factor (unitless)	1	NCRP 1996
tb	Long Term Deposition and Buildup (day)	10950	NCRP 1996
tv	Above Ground Exposure Time (day)	60	NCRP 1996
tw	Weathering Half-life (day)	14	NCRP 1996
Yv	Plant Yield - wet (kg/m2)	2	NCRP 1996
P	Area Density for Root Zone (kg/m2)	240	Hoffman, F. O., R. H. Gardner, and K. F. Eckerman. 1982; Peterson, H. T., Jr. 1983; McKone, T. E. 1994
MLFproduce	Produce Plant Mass Loading Factor (unitless)	0.26 x 0.052 = 0.0135	Hinton, 1992. U.S. EPA SSG 1996 table G-1. Dry weight to wet weight conversion equation from section 4.10.7.
IFWres-adj	Resident Tap Water Ingestion Rate - age-adjusted (L)	19,138	Calculated using the age-adjusted intake factors equation.
IRWres-a	Resident Tap Water Ingestion - adult (L/day)	2.5	U.S. EPA 2011a, Tables 3-15 and 3-33; weighted average of 90th percentile consumer-only ingestion of drinking water (21+)
IRWres-c	Resident Tap Water Ingestion - child (L/day)	0.78	U.S. EPA 2011a, Tables 3-15 and 3-33; weighted average of 90th percentile consumer-only ingestion of drinking water (birth to < years)
IFAres-adj	Resident Inhalation Rate - age-adjusted (m3)	161,100	Calculated using the age-adjusted intake factors equation.
DFAres-adj	Resident Immersion Factor - age-adjusted (hours)	6104	Calculated using the age-adjusted intake factors equation.
IRAres-a	Resident Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRAres-c	Resident Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
IFVres-adj	Resident Vegetable Ingestion Fraction - age-adjusted (g)	989,870	Calculated using the age-adjusted intake factors equation
IRVres-a	Resident Vegetable Ingestion Rate - adult (g/day)	128.9	U.S. EPA 2011 (Table 13-10)
IRVres-c	Resident Vegetable Ingestion Rate - child (g/day)	41.7	U.S. EPA 2011 (Table 13-10)
IFFres-adj	Resident Fruit Ingestion Fraction - age-adjusted (g)	1,462,510	Calculated using the age-adjusted intake factors equation
IRFres-a	Resident Fruit Ingestion Rate - adult (g/day)	188.5	U.S. EPA 2011 (Table 13-5)
IRFres-c	Resident Fruit Ingestion Rate - child (g/day)	68.1	U.S. EPA 2011 (Table 13-5)
EFres	Resident Exposure Frequency - (days/year)	350	U.S. EPA 1991a (pg. 15)
EFres-a	Resident Exposure Frequency - adult (days/year)	350	U.S. EPA 1991a (pg. 15)
EFres-c	Resident Exposure Frequency - child (days/year)	350	U.S. EPA 1991a (pg. 15)
EDres	Resident Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
EDres-a	Resident Exposure Duration - adult (years)	20	EDres (26 years) - EDres-c (6 years)
EDres-c	Resident Exposure Duration - child (years)	6	U.S. EPA 1991a, Pages 6 and 15
ETevent-res-a	Resident Tap Water Exposure Time - Adult (hours/event)	0.71	U.S. EPA 1997a
ETevent-res-c	Resident Tap Water Exposure Time - Child (hours/event)	0.54	U.S. EPA 1997a
EVres-a	Number of bathing events per day - adult resident (events/day)	1	U.S. EPA 2004 Exhibit 3-2
EVres-c	Number of bathing events per day - child resident (events/day)	1	U.S. EPA 2004 Exhibit 3-2

Table 12. Indoor Worker Tap Water

Symbol	Definition (units)	Default	Reference
CDIind-wat-ing	Indoor Worker Tap Water Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIind-wat-inh	Indoor Worker Tap Water Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIind-wat-imm	Indoor Worker Tap Water Radionuclide Immersion (pCi/L-year)	Contaminant-specific	Determined in this calculator
IRWind	Indoor Worker Tap Water Ingestion (L/day)	1.25	U.S. EPA 2014, FAQ 13
EFind	Indoor Worker Exposure Frequency (days/year)	250	U.S. EPA 1991a (pg. 15)
EDind	Indoor Worker Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETind	Indoor Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day
ETevent-ind	Indoor Worker Tap Water Exposure Time - adult (hours/event)	0.71	U.S. EPA 1997a
EVind	Number of bathing events per day - Indoor Worker (events/day)	1	U.S. EPA 2004 Exhibit 3-2

Table 13. Recreator Surface Water

Symbol	Definition (units)	Default	Reference
CDIrec-wat-ing	Recreator Surface Water Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIrec-wat-imm	Recreator Surface Water Radionuclide Immersion (pCi-year/L)	Contaminant-specific	Determined in this calculator
CDIrec-wat-fowl-ing	Recreator Fowl Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIrec-wat-game-ing	Recreator Game Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
IFWrec-adj	Recreator Surface Water Ingestion - age-adjusted (L)	131.4	Calculated using the age-adjusted intake factors equation.
IRWrec-a	Recreator Surface water Ingestion - adult (L/hour)	0.11	Time weighted average was calculated based on the upper percentile from Table 3.7 of EFH 2019
IRWrec-c	Recreator Surface water Ingestion - child (L/hour)	0.12	Table 3.5 in EFH 2011
DFArec-adj	Recreator Immersion Factor - age-adjusted (hours)	1,170	Calculated using the age-adjusted intake factors equation.
EFrec	Recreator Exposure Frequency - (days/year)	45	Region 4 Bulletin
EFrec-c	Recreator Exposure Frequency - child (days/year)	45	Region 4 Bulletin
EFrec-a	Recreator Exposure Frequency - adult (days/year)	45	Region 4 Bulletin
EDrec	Recreator Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
EDrec-a	Recreator Exposure Duration - adult (years)	20	EDres (26 years) - EDres-c (6 years)
EDrec-c	Recreator Exposure Duration - child (years)	6	U.S. EPA 1991a, Pages 6 and 15
ETevent-rec-a	Number of bathing events per day - adult recreator (events/day)	1	reasonable estimate. See 4.7.5
ETevent-rec-c	Number of hours per bathing event - child recreator (hours/event)	1	reasonable estimate. See 4.7.5
EVrec-a	Number of hours per bathing event - child recreator (hours/event)	1	reasonable estimate. See 4.7.5
EVrec-c	Number of bathing events per day - child recreator (events/day)	1	reasonable estimate. See 4.7.5
IRGLrec-game	Recreator Land Game Ingestion Rate (g/day)	Site-specific	Site-specific
IRGFrec-fowl	Recreator Fowl Ingestion Rate (g/day)	Site-specific	Site-specific
TFbeef	Game Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFpoultry	Fowl Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Qw-game	Game Water Intake Rate (L/day)	Site-specific	Site-specific
Qw-fowl	Fowl Water Intake Rate (L/day)	Site-specific	Site-specific
fw-game	Fraction of Animal's Water from Site when On-Site - game (unitless)	1	Assumes 100%
fw-fowl	Fraction of Animal's Water from Site when On-Site - fowl (unitless)	1	Assumes 100%

Table 14. Farmer Tap Water

Symbol	Definition (units)	Default	Reference
CDIfar-wat-ing	Farmer Tap Water (Groundwater) Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-inh	Farmer Tap Water (Groundwater) Radionuclide Inhalation (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-imm	Farmer Tap Water (Groundwater) Radionuclide Immersion (pCi-year/L)	Contaminant-specific	Determined in this calculator
CDIfar-wat-produce-ing	Farmer Produce Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-poultry-ing	Farmer Poultry Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-egg-ing	Farmer Egg Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-beef-ing	Farmer Beef Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-dairy-ing	Farmer Dairy Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-swine-ing	Farmer Swine Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-wat-fsh-ing	Farmer Fish Radionuclide Back-calculated Concentration in Water Ingestion (pCi)	Contaminant-specific	Determined in this calculator
ρm	Density of milk (kg/L)	1.03	Milk Composition & Synthesis Resource Library
BCF	Fish Transfer Factor (L/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFbeef	Beef Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFdairy	Dairy Transfer Factor (day/L)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFswine	Swine Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFpoultry	Poultry Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
TFegg	Egg Transfer Factor (day/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
Qw-beef	Beef Water Intake Rate (L/day)	53	U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
Qw-dairy	Dairy Water Intake Rate (L/day)	92	U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
Qw-swine	Swine Water Intake Rate (L/day)	11.4	NEC, Swine Nutrition Guide (pg. 19). U.S. EPA 1998 (pg B-180)
Qw-poultry	Poultry Water Intake Rate (L/day)	0.4	U.S. EPA 2005 (pg. B-159/165), NRC 1994 pg. 15 (Qw = 2 × Qp)
Irrrup	root uptake from irrigation multiplier	Isotope-specific	Calculated
Irrres	resuspension from irrigation multiplier	Isotope-specific	Calculated
Irrdep	Aerial deposition from irrigation multiplier	Isotope-specific	Calculated
Bvwet	Soil to Plant Transfer Factor - wet (pCi/g-fresh plant per pCi/g-dry soil)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
F	Irrigation Period (unitless)	0.25	Personal communication
If	Interception Fraction (unitless)	0.42	Miller, C. W. 1980
Ir	Irrigation Rate (L/m2)	3.62	Personal communication
λHL	Soil Leaching Rate (1/day)	0.000027	NCRP 1996
λi	decay (1/day)	0.693/TR - radionuclides	NCRP 1996
λE	Decay for Removal on Produce (1/day)	λi + (0.693/tw)	NCRP 1996
λB	Effective Rate for Removal (1/day)	λHL - λi	NCRP 1996
T	Translocation Factor (unitless)	1	NCRP 1996
tb	Long Term Deposition and Buildup (day)	10950	NCRP 1996
tv	Above Ground Exposure Time (day)	60	NCRP 1996
tw	Weathering Half-life (day)	14	NCRP 1996
Yv	Plant Yield - wet (kg/m2)	2	NCRP 1996
P	Area Density for Root Zone (kg/m2)	240	Hoffman, F. O., R. H. Gardner, and K. F. Eckerman. 1982; Peterson, H. T., Jr. 1983; McKone, T. E. 1994
MLFproduce	Produce Plant Mass Loading Factor (unitless)	0.26 x 0.052 = 0.0135	Hinton, 1992. U.S. EPA SSG 1996 table G-1. Dry weight to wet weight conversion equation from section 4.10.7.
IFWfar-adj	Farmer Water Ingestion Fraction - age-adjusted (L)	31,388	Calculated using the age-adjusted intake factors equation.
IRWfar-a	Farmer Water Ingestion Rate - adult (L/day)	2.5	U.S. EPA 2011a, Tables 3-15 and 3-33; weighted average of 90th percentile consumer-only ingestion of drinking water (21+)
IRWfar-c	Farmer Water Ingestion Rate - child (L/day)	0.78	U.S. EPA 2011a, Tables 3-15 and 3-33; weighted average of 90th percentile consumer-only ingestion of drinking water (birth to < years)
IFAfar-adj	Farmer Inhalation Rate - age-adjusted (m3)	259,000	Calculated using the age-adjusted intake factors equation.
DFAfar-adj	Farmer Immersion Factor - age-adjusted (hours)	9583	Calculated using the age-adjusted intake factors equation.
IRAfar-a	Farmer Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRAfar-c	Farmer Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
EFfar	Farmer Exposure Frequency (days/year)	350	U.S. EPA 1991a (pg. 15)
EFfar-a	Farmer Exposure Frequency - adult (days/year)	350	U.S. EPA 1991a (pg. 15)
EFfar	Farmer Exposure Frequency - child (days/year)	350	U.S. EPA 1991a (pg. 15)
EDfar	Farmer Exposure Duration (years)	40	U.S. EPA 2005 (Table 6-3)
EDfar-a	Farmer Exposure Duration - adult (years)	34	U.S. EPA 1994a
EDfar-c	Farmer Exposure Duration - child (years)	6	U.S. EPA 2005 (Table 6-3)
ETevent-far-c	Farmer Tap Water Exposure Time - Child (hours/day)	0.54	U.S. EPA 1997a
ETevent-far-a	Farmer Tap Water Exposure Time - Adult (hours/day)	0.71	U.S. EPA 1997a
EVfar-a	Number of bathing events per day - adult farmer (events/day)	1	U.S. EPA 2004 Exhibit 3-2
EVfar-c	Number of bathing events per day - child farmer (events/day)	1	U.S. EPA 2004 Exhibit 3-2

Table 15. Resident Air

Symbol	Definition (units)	Default	Reference
CDIres-air-inh-decay	Resident Air Radionuclide Inhalation w/ Decay (pCi)	Contaminant-specific	Determined in this calculator
CDIres-air-sub-decay	Resident Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIres-air-inh-nodecay	Resident Air Radionuclide Inhalation w/out Decay (pCi)	Contaminant-specific	Determined in this calculator
CDIres-air-sub-nodecay	Resident Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
tres	Time - resident (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
IFAres-adj	Resident Inhalation Rate - age-adjusted (m3)	161,100	Calculated using the age-adjusted intake factors equation.
IRAres-a	Resident Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRAres-c	Resident Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
EFres	Resident Exposure Frequency - (days/year)	350	U.S. EPA 1991a (pg. 15)
EFres-c	Resident Exposure Frequency - child (days/year)	350	U.S. EPA 1991a (pg. 15)
EFres-a	Resident Exposure Frequency - adult (days/year)	350	U.S. EPA 1991a (pg. 15)
EDres	Resident Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
EDres-a	Resident Exposure Duration - adult (years)	20	EDres (26 years) - EDres-c (6 years)
EDres-c	Resident Exposure Duration - child (years)	6	U.S. EPA 1991a, Pages 6 and 15
ETres	Resident Exposure Time (hours/day)	24	24 Hours per 24 hour Day
ETres-a	Resident Exposure Time - adult (hours/day)	24	24 Hours per 24 hour Day
ETres-c	Resident Exposure Time - child (hours/day)	24	24 Hours per 24 hour Day

Table 16. Indoor Worker Air

Symbol	Definition (units)	Default	Reference
CDIind-air-inh-decay	Indoor Worker Air Radionuclide Inhalation w/ Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIind-air-sub-decay	Indoor Worker Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIind-air-inh-nodecay	Indoor Worker Air Radionuclide Inhalation w/out Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIind-air-sub-nodecay	Indoor Worker Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
IRAind	Indoor Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFind	Indoor Worker Exposure Frequency (days/year)	250	U.S. EPA 1991a (pg. 15)
EDind	Indoor Worker Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETind	Indoor Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 17. Outdoor Worker Air

Symbol	Definition (units)	Default	Reference
CDIout-air-inh-decay	Outdoor Worker Air Radionuclide Inhalation w/ Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIout-air-sub-decay	Outdoor Worker Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIout-air-inh-nodecay	Outdoor Worker Air Radionuclide Inhalation w/out Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIout-air-sub-nodecay	Outdoor Worker Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
tout	Time - outdoor worker (years)	25	U.S. EPA 1991a (pg. 15)
IRAout	Outdoor Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFout	Outdoor Worker Exposure Frequency (days/year)	225	U.S. EPA 1991a (pg. 15)
EDout	Outdoor Worker Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETout	Outdoor Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 18. Composite Worker Air

Symbol	Definition (units)	Default	Reference
CDIcom-air-inh-decay	Composite Worker Air Radionuclide Inhalation w/ Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIcom-air-sub-decay	Composite Worker Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIcom-air-inh-nodecay	Composite Worker Air Radionuclide Inhalation w/out Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIcom-air-sub-nodecay	Composite Worker Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
tcom	Time - worker (years)	25	U.S. EPA 1991a (pg. 15)
IRAcom	Composite Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFcom	Composite Worker Exposure Frequency (days/year)	250	U.S. EPA 1991a (pg. 15)
EDcom	Composite Exposure Duration (years)	25	U.S. EPA 1991a (pg. 15)
ETcom	Composite Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 19. Excavation Worker Air

Symbol	Definition (units)	Default	Reference
CDIexc-air-inh-decay	Excavation Worker Air Radionuclide Inhalation w/ Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIexc-air-sub-decay	Excavation Worker Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIexc-air-inh-nodecay	Excavation Worker Air Radionuclide Inhalation w/out Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIexc-air-sub-nodecay	Excavation Worker Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
texc	Time - excavation worker (years)	1	U.S. EPA 2002 Exhibit 5-1
IRAexc	Excavation Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFexc	Excavation Worker Exposure Frequency (days/year)	20	Based on 5 days per week for 4 weeks
EDexc	Excavation Worker Exposure Duration (years)	1	U.S. EPA 2002 Exhibit 5-1
ETexc-o	Excavation Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 20. Construction Worker Air

Symbol	Definition (units)	Default	Reference
CDIcon-air-inh-decay	Construction Worker Air Radionuclide Inhalation w/ Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIcon-air-sub-decay	Construction Worker Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIcon-air-inh-nodecay	Construction Worker Air Radionuclide Inhalation w/out Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIcon-air-sub-nodecay	Construction Worker Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
tcon	Time - construction worker (years)	1	U.S. EPA 2002 Exhibit 5-1
IRAcon	Construction Worker Inhalation Rate (m3/day; based on a rate of 2.5m3/hour for 24 hours)	60	U.S. EPA 1997a (pg. 5-11)
EFcon	Construction Worker Exposure Frequency (days/year)	250	U.S. EPA 2002 Exhibit 5-1
EWcon	Construction Worker Exposure Frequency (weeks/year)	50	U.S. EPA 2002 Exhibit 5-1
DWcon	Construction Worker Exposure Frequency (days/week)	5	U.S. EPA 2002 Exhibit 5-1
EDcon	Construction Worker Exposure Duration (years)	1	U.S. EPA 2002 Exhibit 5-1
ETcon	Construction Worker Exposure Time (hours/day)	8	Eight Hours per 24 hour Day

Table 21. Recreator Air

Symbol	Definition (units)	Default	Reference
CDIrec-air-inh-decay	Recreator Worker Air Radionuclide Inhalation w/ Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIrec-air-sub-decay	Recreator Worker Air Radionuclide Submersion w/ Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
CDIrec-air-inh-nodecay	Recreator Worker Air Radionuclide Inhalation w/out Decay (pCi/m3)	Contaminant-specific	Determined in this calculator
CDIrec-air-sub-nodecay	Recreator Air Radionuclide Submersion w/out Decay (pCi-year/m3)	Contaminant-specific	Determined in this calculator
trec	Time - recreator (years)	Site-specific	Site-specific
IFArec-adj	Recreator Inhalation Fraction - age-adjusted (m3)	1,437.5	Calculated using the age-adjusted intake factors equation.
IRArec-a	Recreator Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRArec-c	Recreator Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
EFrec	Recreator Exposure Frequency - (days/year)	75	Reasonable estimate. See 4.7.3
EFrec-a	Recreator Exposure Frequency - adult (days/year)	75	Reasonable estimate. See 4.7.3
EFrec-c	Recreator Exposure Frequency - child (days/year)	75	Reasonable estimate. See 4.7.3
EDrec	Recreator Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
EDrec-a	Recreator Exposure Duration - adult (years)	20	EDres (26 years) - EDres-c (6 years)
EDrec-c	Recreator Exposure Duration - child (years)	6	U.S. EPA 1991a, Pages 6 and 15
ETrec	Recreator Exposure Time (hours/day)	1	Reasonable estimate. See 4.7.3
ETrec-a	Recreator Exposure Time - adult (hours/day)	1	Reasonable estimate. See 4.7.3
ETrec-c	Recreator Exposure Time - child (hours/day)	1	Reasonable estimate. See 4.7.3

Table 22. Resident Fish Consumption

Symbol	Definition (units)	Default	Reference
CDIres-fsh-ing	Resident Fish Radionuclide (pCi)	Contaminant-specific	Determined in this calculator
CDIres-fshw-ing	Resident Surface Water Fish Radionuclide (pCi)	Contaminant-specific	Determined in this calculator
BCF	Fish Transfer Factor (L/kg)	Radionuclide-specific	Hierarchy selection in Section 2.3.2
IRFres	Resident Fish Ingestion Rate (g/day)	54	U.S. EPA 1991a (page 15)
EFres	Resident Exposure Frequency - (days/year)	350	U.S. EPA 1991a (pg. 15)
EDres	Resident Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.

Table 23. Recreator Game and Fowl Consumption

Symbol	Definition (units)	Default	Reference
CDIrec-fowl-ing	Recreator Fowl Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIrec-game-ing	Recreator Game Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CFrec-game	Game Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFrec-fowl	Fowl Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
EFrec	Recreator Exposure Frequency - (days/year)	Site-specific	Site-specific
EDrec	Recreator Exposure Duration (years)	26	U.S. EPA 2011a, Table 16-108; 90th percentile or current residence time.
IRGLrec-game	Recreator Land Game Ingestion Rate (g/day)	Site-specific	Site-specific
IRGFrec-fowl	Recreator Fowl Ingestion Rate (g/day)	Site-specific	Site-specific

Table 24. Farmer Direct Ingestion

Symbol	Definition (units)	Default	Reference
CDIfar-produce-ing	Farmer Produce Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-poultry-ing	Farmer Poultry Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-egg-ing	Farmer Egg Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-beef-ing	Farmer Beef Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-dairy-ing	Farmer Dairy Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-swine-ing	Farmer Swine Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CDIfar-fsh-ing	Farmer Fish Radionuclide Ingestion (pCi)	Contaminant-specific	Determined in this calculator
CFfar-produce	Produce Contaminated Fraction - farmer (unitless)	1	U.S. EPA 1994c. U.S. EPA. 1998. (pg. C-9)
CFfar-poultry	Poultry Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFfar-egg	Egg Contaminated Fraction - Farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFfar-beef	Beef Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFfar-dairy	Dairy Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFfar-swine	Swine Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
CFfar-fish	Fish Contaminated Fraction - farmer (unitless)	1	Developed for Radionuclide Soil Screening calculator
IFVfar-adj	Farmer Vegetable Ingestion Fraction - age-adjusted (g)	1,583,400	Calculated using the age-adjusted intake factors equation
IRVfar-a	Farmer Vegetable Ingestion Rate - adult (g/day)	125.7	U.S. EPA 2011 (Table 13-10)
IRVfar-c	Farmer Vegetable Ingestion Rate - child (g/day)	41.7	U.S. EPA 2011 (Table 13-10)
IFFfar-adj	Farmer Fruit Ingestion Rate - age-adjusted (g)	2,246,930	Calculated using the age-adjusted intake factors equation
IRFfar-a	Farmer Fruit Ingestion Rate - adult (g/day)	176.8	U.S. EPA 2011 (Table 13-5)
IRFfar-c	Farmer Fruit Ingestion Rate - child (g/day)	68.1	U.S. EPA 2011 (Table 13-5)
IFPfar-adj	Farmer Poultry Ingestion Fraction - age-adjusted (g)	1,318,100	Calculated using the age-adjusted intake factors equation
IRPfar-a	Farmer Poultry Ingestion Rate - adult (g/day)	106.6	U.S. EPA 2011 (Table 13-52)
IRPfar-c	Farmer Poultry Ingestion Rate - child (g/day)	23.6	U.S. EPA 2011 (Table 13-52)
IFEfar-adj	Farmer Egg Ingestion Rate - age-adjusted (g)	658,455	Calculated using the age-adjusted intake factors equation
IREfar-a	Farmer Egg Ingestion Rate - adult (g/day)	53.4	U.S. EPA 2011 (Table 13-40)
IREfar-c	Farmer Egg Ingestion Rate - child (g/day)	10.95	U.S. EPA 2011 (Table 13-40)
IFBfar-adj	Farmer Beef Ingestion Fraction - age-adjusted (g)	2,202,410	Calculated using the age-adjusted intake factors equation
IRBfar-a	Farmer Beef Ingestion Rate - adult (g/day)	178.0	U.S. EPA 2011 (Table 13-33)
IRBfar-c	Farmer Beef Ingestion Rate - child (g/day)	40.1	U.S. EPA 2011 (Table 13-33)
IFDfar-adj	Farmer Dairy Ingestion Fraction - age-adjusted (g)	6,036,590	Calculated using the age-adjusted intake factors equation
IRDfar-a	Farmer Dairy Ingestion Rate - adult (g/day)	445.6	U.S. EPA 2011 (Table 11-4)
IRDfar-c	Farmer Dairy Ingestion Rate - child (g/day)	349.5	U.S. EPA 2011 (Table 11-4)
IFSWfar-adj	Farmer Swine Ingestion Fraction - age-adjusted (g)	1,203,860	Calculated using the age-adjusted intake factors equation
IRSWfar-a	Farmer Swine Ingestion Rate - adult (g/day)	97.9	U.S. EPA 2011 (Table 13-51)
IRSWfar-c	Farmer Swine Ingestion Rate - child (g/day)	18.5	U.S. EPA 2011 (Table 13-51)
IFFIfar-adj	Farmer Fish Ingestion Fraction - age-adjusted (g)	1,918,140	Calculated using the age-adjusted intake factors equation
IRFIfar-a	Farmer Fish Ingestion Rate - adult (g/day)	155.4	U.S. EPA 2011 (Table 13-20)
IRFIfar-c	Farmer Fish Ingestion Rate - child (g/day)	32.8	U.S. EPA 2011 (Table 13-20)

Table 25. Soil to Groundwater SSL Factor Variables

Symbol	Definition (units)	Default	Reference
Cw	Target soil leachate concentration (pCi/L)	Nonzero MCL or RSL × DAF	U.S. EPA. 2002 Equation 4-14
DAF	Dilution attenuation factor (unitless)	20 (or site-specific)	U.S. EPA. 2002 Equation 4-11
EDgw	Exposure duration	70	U.S. EPA. 2002 Equation 4-14
I	Infiltration Rate (m/year)	0.18	U.S. EPA. 2002 Equation 4-11
L	Source length parallel to ground water flow (m)	Site-specific	U.S. EPA. 2002 Equation 4-11
i	Hydraulic gradient (m/m)	Site-specific	U.S. EPA. 2002 Equation 4-11
K	Aquifer hydraulic conductivity (m/year)	Site-specific	U.S. EPA. 2002 Equation 4-11
θw	Water-filled soil porosity (Lwater/Lsoil)	0.3	U.S. EPA. 2002 Equation 4-10
θa	Air-filled soil porosity (Lair/Lsoil)	= n-θw	U.S. EPA. 2002 Equation 4-10
n	Total soil porosity(Lpore/Lsoil)	= 1-(ρb/ρs)	U.S. EPA. 2002 Equation 4-10
ρs	Soil particle density (Kg/L)	2.65	U.S. EPA. 2002 Equation 4-10
ρb	Dry soil bulk density (kg/L)	1.5	U.S. EPA. 2002 Equation 4-10
Kd	soil-water partition coefficient (L/kg)	= Koc*foc for organics	U.S. EPA. 2002 Equation 4-10
da	Aquifer thickness (m)	Site-specific	U.S. EPA. 2002 Equation 4-10
ds	Depth of source (m)	Site-specific	U.S. EPA. 2002 Equation 4-10
d	Mixing zone depth (m)	Site-specific	U.S. EPA. 2002 Equation 4-12

Table 26. Wind Particulate Emission Factor Variables

Symbol	Definition (units)	Default	Reference
PEF	Particulate Emission Factor Wind - Minneapolis (m3/kg)	1.36 x 109(region-specific)	U.S. EPA 2002 Exhibit D-2
Q/Cwind	Inverse of the Mean Concentration at the Center of a 0.5-Acre-Square Source (g/m2-s per kg/m3)	93.77 (region-specific)	U.S. EPA 2002 Exhibit D-2
V	Fraction of Vegetative Cover (unitless)	0.5	U.S. EPA. 2002 Equation 4-5
Um	Mean Annual Wind Speed (m/s)	4.69	U.S. EPA. 2002 Equation 4-5
Ut	Equivalent Threshold Value of Wind Speed at 7m (m/s)	11.32	U.S. EPA. 2002 Equation 4-5
F(x)	Function Dependent on Um/Ut (unitless)	0.194	U.S. EPA. 2002 Equation 4-5
A	Dispersion constant unitless	PEF and region-specific	U.S. EPA 2002 Exhibit D-2
As	Areal extent of the site or contamination (acres)	0.5 (range 0.5 to 500 )	U.S. EPA 2002 Exhibit D-2
B	Dispersion constant unitless	PEF and region-specific	U.S. EPA 2002 Exhibit D-2
C	Dispersion constant unitless	PEF and region-specific	U.S. EPA 2002 Exhibit D-2

Table 27. Mechanical Particulate Emission Factor Variables from Vehicle Traffic

Symbol	Definition (units)	Default	Reference
PEFsc	Particulate Emission Factor - subchronic (m3/kg)	(Site-specific)	U.S. EPA 2002 Equation 5-5
Q/Csr	Inverse of the ratio of the 1-h geometric mean concentration to the emission flux along a straight road segment bisecting a square site (g/m2-s per kg/m3)	23.02 (for 0.5 acre site)	U.S. EPA 2002 Equation 5-5
FD	Dispersion correction factor (unitless)	0.185	U.S. EPA 2002 Equation 5-5
T	Total time over which construction occurs (s)	7,200,000	U.S. EPA 2002 Equation 5-5
AR	Surface area of contaminated road segment (m2)	(AR = LR x WR x 0.092903m2 /ft2 )	U.S. EPA 2002 Equation 5-5
LR	Length of road segment (ft)	Site-specific	U.S. EPA 2002 Equation 5-5
WR	Width of road segment (ft)	20	U.S. EPA 2002 Equation E-18
W	Mean vehicle weight (tons)	(Number of cars x tons/car + number of trucks x tons/truck) / total vehicles)	U.S. EPA 2002 Equation 5-5
p	Number of days with at least 0.01 inches of precipitation (days/year)	Site-specific	U.S. EPA 2002 Exhibit 5-2
∑VKT	Sum of fleet vehicle kilometers traveled during the exposure duration (km)	∑VKT = total vehicles x distance (km/day) x frequency (weeks/year) x (days/year)	U.S. EPA 2002 Equation 5-5
A	Dispersion constant unitless	12.9351	U.S. EPA 2002 Equation 5-6
As	Areal extent of site surface soil contamination (acres)	0.5 (range 0.5 to 500)	U.S. EPA 2002 Equation 5-6
B	Dispersion constant unitless	5.7383	U.S. EPA 2002 Equation 5-6
C	Dispersion constant unitless	71.7711	U.S. EPA 2002 Equation 5-6

Table 28. Mechanical Particulate Emission Factor Variables from other than Vehicle Traffic

Symbol	Definition (units)	Default	Reference
PEF'sc	Particulate Emission Factor - subchronic (m3/kg)	(Site-specific)	U.S. EPA 2002 Equation E-26
Q/Csa	Inverse of the ratio of the 1-h geometric mean air concentration and the emission flux at the center of the square emission source (g/m2-s per kg/m3)	Site-specific	U.S. EPA 2002 Equation E-15
FD	Dispersion correction factor (unitless)	0.185	U.S. EPA 2002 Equation E-16
A	Dispersion constant unitless	2.4538	U.S. EPA 2002 Equation E-15
B	Dispersion constant unitless	17.5660	U.S. EPA 2002 Equation E-15
C	Dispersion constant unitless	189.0426	U.S. EPA 2002 Equation E-15
As	Areal extent of site surface soil contamination (acres)	(range 0.5 to 500)	U.S. EPA 2002 Equation E-15
J'T (g/m2-s)	Total time-averaged PM10 unit emission flux for construction activities other than traffic on unpaved roads	Site-specific	U.S. EPA 2002 Equation E-25
MPCwind	Unit mass emitted from wind erosion (g)	Site-specific	U.S. EPA 2002 Equation E-20
V	Fraction of Vegetative Cover (unitless)	0	U.S. EPA 2002 Equation E-20
Um	Mean Annual Wind Speed (m/s)	4.69	U.S. EPA 2002 Equation E-20
Ut	Equivalent Threshold Value of Wind Speed at 7m (m/s)	11.32	U.S. EPA 2002 Equation E-20
F(x)	Function Dependent on Um/Ut (unitless)	0.194	U.S. EPA 2002 Equation E-20
Asurf	Areal extent of site surface soil contamination (m2)	(range 0.5 to 500)	U.S. EPA 2002 Equation E-20
ED	Exposure duration (years)	Site-specific	U.S. EPA 2002 Equation E-20
Mexcav	Unit mass emitted from excavation soil dumping (g)	Site-specific	U.S. EPA 2002 Equation E-21
0.35	PM10 particle size multiplier (unitless)	0.35	U.S. EPA 2002 Equation E-21
Um	Mean annual wind speed during construction (m/s)	4.69	U.S. EPA 2002 Equation E-21
Mm-excav	Gravimetric soil moisture content (%)	12 (mean value for municipal landfill cover)	U.S. EPA 2002 Equation E-21
ρsoil	In situ soil density (includes water) (Mg/m3)	1.68	U.S. EPA 2002 Equation E-21
Aexcav	Areal extent of excavation (m2)	(range 0.5 to 500)	U.S. EPA 2002 Equation E-21
dexcav	Average depth of excavation (m)	Site-specific	U.S. EPA 2002 Equation E-21
NA-dump	Number of times soil is dumped (unitless)	2	U.S. EPA 2002 Equation E-21
Mdoz	Unit mass emitted from dozing operations (g)	Site-specific	U.S. EPA 2002 Equation E-22
0.75	PM10 scaling factor (unitless)	0.75	U.S. EPA 2002 Equation E-22
sdoz	Soil silt content (%)	6.9	U.S. EPA 2002 Equation E-22
Mm-doz	Gravimetric soil moisture content (%)	7.9 (mean value for overburden)	U.S. EPA 2002 Equation E-22
∑VKTdoz	Sum of dozing kilometers traveled (km)	Site-specific	U.S. EPA 2002 Equation E-22
Sdoz	Average dozing speed (kph)	11.4 (mean value for graders)	U.S. EPA 2002 Equation E-22
NA-doz	Number of times site is dozed (unitless)	Site-specific	U.S. EPA 2002 Equation E-22
Bd	Dozer blade length (m)	Site-specific	U.S. EPA 2002 Page E-28
Mgrade	Unit mass emitted from grading operations (g)	Site-specific	U.S. EPA 2002 Equation E-23
0.60	PM10 scaling factor (unitless)	0.60	U.S. EPA 2002 Equation E-23
∑VKTgrade	Sum of grading kilometers traveled (km)		U.S. EPA 2002 Equation E-23
Sgrade	Average grading speed (kph)	11.4 (mean value for graders)	U.S. EPA 2002 Equation E-23
NA-grade	Number of times site is graded (unitless)	Site-specific	U.S. EPA 2002 Equation E-23
Bg	Grader blade length (m)	Site-specific	U.S. EPA 2002 Page E-28
Mtill	Unit mass emitted from tilling operations (g)	Site-specific	U.S. EPA 2002 Equation E-24
still	Soil silt content (%)	18	U.S. EPA 2002 Equation E-24
Ac-till	Areal extent of tilling (acres)	Site-specific	U.S. EPA 2002 Equation E-24
Ac-grade	Areal extent of grading (acres)	Site-specific	Necessary to solve ∑VKTgrade in U.S. EPA 2002 Equation E-23
Ac-doz	Areal extent of dozing (acres)	Site-specific	Necessary to solve ∑VKTdoz in U.S. EPA 2002 Equation E-22
NA-till	Number of times soil is tilled (unitless)	2	U.S. EPA 2002 Equation E-24

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ANL 1993. Manual for Implementing Residual Radioactive Materials Guidelines Using RESRAD, Version 5.0. Argonne National Laboratory, Argonne, IL. ANL/EAD/LD-2

Calabrese E.J., Barnes R., Stanek III E.J., Pastides H., Gilbert CE, Veneman P., Wang XR, Lasztity A., and Kostecki P.T. How much soil do young children ingest: an epidemiologic study. Regul Toxicol Pharmacol 1989: 10(2):123-137.

Davis, S; Waller, P; Buschbom, R; Ballou, J; White, P. (1990). Quantitative estimates of soil ingestion in normal children between the ages of 2 and 7 years: Population-based estimates using aluminum, silicon, and titanium as soil tracer elements. Arch Environ Health 45: 112-122.

Etnier 1980. Till, J. E., H. R. Meyer, E. L. Etnier, E. S. Bomar, R. D. Gentry, G. G. Killough, P. S. Rohwer, V. J. Tennery, and C. C. Travis Tritium-An Analysis of Key Environmental and Dosimetric Questions. ORNL/TM-6990. pg 15.

Hinton, T. G. 1992. Contamination of plants by resuspension: a review, with critique of measurement methods. Sci. Total Environ. 121:171-193

IAEA 1994. Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments. International Atomic Energy Agency

ICRP 2008. Nuclear Decay Data for Dosimetric Calculations. ICRP Publication 107. Ann. ICRP 38 (3).

MILLER Ch. W. (1980): An analysis of measured values for the fraction of a radiocative aerosol intercepted by vegetation. Health Physics, 38: 705 - 712.

NEC. Swine Nutrition Guide. Cooperative Extension Service / South Dakota State University and University of Nebraska / U.S. Department of Agriculture. Nebraska Cooperative Extension EC 95-273-C.

The pig water ingestion numbers are derived from the USDA "Swine Nutrition Guide" and the EPA Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities, found here. USDA assumes a pig consumes 1/4 to 1/3 gallons of water for every pound of dry feed. The midpoint of this range (7/24 gallons of water per 1 lbs. of dry feed) was used with the default dry feed, (4.7 kg) from the U.S. EPA, to come up with 3 gallons (11.4 L) per day default water intake.

NCRP 1996. Screening Models for Releases of Radionuclides to Atmosphere, Surface Water, and Ground, Vols. 1 and 2, NCRP Report No. 123. National Council on Radiation Protection and Measurements. http://www.ncrp.com/rpt123.html

NRC 1994. Nutrient Requirements of Poultry: Ninth Revised Edition, 1994. Washington, DC: The National Academies Press, 1994.

ORNL 2014a. Area Correction Factors for Contaminated Soil for Use in Risk and Dose Assessment Models and appendix. Center for Radiation Protection Knowledge. September 2014.

ORNL 2014b. Gamma Shielding Factors for Soil Covered Contamination for Use in Risk and Dose Assessment Models and appendix. Center for Radiation Protection Knowledge. September 2014.

ORNL 2014c. Calculation of Slope Factors and Dose Coefficients and appendix. Center for Radiation Protection Knowledge. September 2014.

U.S. EPA 1988. U.S. Environmental Protection Agency (U.S. EPA). Superfund Exposure Assessment Manual (SEAM). Office of Solid Waste and Emergency Response. OSWER Directive 9285.5-1. EPA/540/1-881001.

U.S. EPA 1989. U.S. Environmental Protection Agency (U.S. EPA). Risk assessment guidance for Superfund. Volume I: Human health evaluation manual (Part A). Interim Final. Office of Emergency and Remedial Response. EPA/540/1-89/002.

U.S. EPA 1990. Interim Final Methodology for Assessing Health Risks Associated with Indirect Exposure to Combustor Emissions. Environmental Criteria and Assessment Office. ORD. EPA-600-90-003. January.

U.S. EPA 1991a. U.S. Environmental Protection Agency (U.S. EPA). Human health evaluation manual, supplemental guidance: "Standard default exposure factors". OSWER Directive 9285.6-03.

U.S. EPA 1991b. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part B, Development of Risk-Based Preliminary Remediation Goals). Office of Emergency and Remedial Response. EPA/540/R-92/003. December 1991

U.S. EPA. 1993. External Exposure to Radionuclides in Air, Water, and Soil. Federal Guidance Report No. 12. Office of Radiation and Indoor Air, Washington, DC. EPA 402-R-93-081. http://www.epa.gov/radiation/federal/index.html

U.S. EPA. 1994a. Estimating Exposure to Dioxin-like Components - Volume III: Site-Specific Assessment Procedure. Review Draft. Office of Research and Development. Washington D.C. EPA/600/6-88/005Cc. June. (Also see U.S. EPA. 1994c for direct link to Table) http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=34762

U.S. EPA 1994b. Radiation Site Cleanup Regulations: Technical Support Documents for the Development of Radiation Cleanup Levels for Soil - Review Draft. Office of Radiation and Indoor Air, Washington, DC. EPA 402-R-96-011A. PDF document View Appendix C here.

U.S. EPA. 1994c. Revised Draft Guidance for Performing Screening Level Risk Analyses at Combustion Facilities Burning Hazardous Wastes. Attachment C, Draft Exposure Assessment Guidance for RCRA Hazardous Waste Combustion Facilities. Office of Emergency and Remedial Response. Office of Solid Waste. December 14. http://www.epa.gov/osw/hazard/tsd/td/combust/finalmact/ssra/05hhrapapc.pdf

U.S. EPA. 1996a. Soil Screening Guidance: User's Guide. Office of Emergency and Remedial Response. Washington, DC. OSWER No. 9355.4-23 http://www.epa.gov/superfund/health/conmedia/soil/index.htm

U.S. EPA. 1996b. Soil Screening Guidance: Technical Background Document. Office of Emergency and Remedial Response. Washington, DC. OSWER No. 9355.4-17A http://www.epa.gov/superfund/health/conmedia/soil/index.htm

U.S. EPA. 1997a. Exposure Factors Handbook. Office of Research and Development, Washington, DC. EPA/600/P-95/002Fa.

U.S. EPA. 1997b. Parameter Guidance Document. National Center for Environmental Assessment, NCEA-0238.

U.S. EPA. 1998. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. Office of Solid Waste, Washington, DC. EPA530-D-98-001A. A secure PDF can be downloaded here.

U.S. EPA. 1999a. Data Collection for the Hazardous Waste Identification Rule. Office of Solid Waste, Washington, DC. http://www.epa.gov/osw/hazard/wastetypes/wasteid/hwirwste/risk.htm The section on cattle fodder, soil and water intakes is here.

U.S. EPA 1999b. Volume II, "Review of Geochemistry and Available Kd Values for Cadmium, Cesium, Chromium, Lead, Plutonium, Radon, Strontium, Thorium, Tritium (3H), and Uranium. Office of Radiation and Indoor Air. Washington, DC. EPA 402-R-99-004B, August 1999. http://www.epa.gov/cgi-bin/claritgw?op-Display&document=clserv:OAR:0232;&rank=4&template=epa

U.S. EPA 1999c. Cancer Risk Coefficients for Environmental Exposure to Radionuclides. Federal Guidance Report No. 13. Office of Radiation and Indoor Air. EPA 402-R-99-001. September 1999. http://www.epa.gov/radiation/federal/index.html

U.S. EPA. 2000a. Soil Screening Guidance for Radionuclides: User's Guide. Office of Emergency and Remedial Response and Office of Radiation and Indoor Air. Washington, DC. OSWER No. 9355.4-16A http://www.epa.gov/superfund/health/contaminants/radiation/radssg.htm

U.S. EPA. 2000b. Soil Screening Guidance for Radionuclides: Technical Background Document. Office of Emergency and Remedial Response and Office of Radiation and Indoor Air. Washington, DC. OSWER No. 9355.4-16 http://www.epa.gov/superfund/health/contaminants/radiation/radssg.htm

U.S. EPA 2002. Role of Background in the CERCLA Cleanup Program. Office of Solid Waste and Emergency Response, April 26, 2002, OSWER 9285.6-07P

U.S. EPA 2002. Supplemental Guidance for Developing Soil Screening Levels for Superfund Sites. OSWER 9355.4-24. December 2002. http://www.epa.gov/superfund/health/conmedia/soil/index.htm

U.S. EPA 2002. Simulating Transport in the Unsaturated Zone: Evaluation and Sensitivity Analyses of Select Computer Models.

U.S. EPA 2004. Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment) Final. OSWER 9285.7-02EP.July 2004.

U.S. EPA. 2005. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. Office of Solid Waste, Washington, DC. http://www.epa.gov/osw/hazard/tsd/td/combust/risk.htm. The pdf is available here.

U.S. EPA. 2011. Exposure Factors Handbook 2011 Edition (Final). National Center for Environmental Assessment, Office of Research and Development. Washington D.C.

U.S. EPA. 2014. OSWER Directive 9200.1-120 and FAQ. Office of Solid Waste and Emergency Response, Washington, DC.

van Wijnen J.H., Clausing P., and Brunekreef B. Estimated soil ingestion by children. Environ Res 1990: 51(2): 147-162.

Pinder, J. E. ,. I., and K. W. McLeod. 1989. Mass loading of soil particles on plant surfaces, Health Phys. 57:935-942.

U.S. EPA. 2018. Region 4 Human Health Risk Assessment Supplemental Guidance. EPA Region 4. March, 2018.

U.S. EPA. 2019. Exposure Factors Handbook Chapter 3 Updates. Office of Research and Development, Washington, DC. EPA/600/R-090/052F