Note

The RAIS presents this updated PRG calculator in response to the following: incorporating chemical-specific parameters from the lastest EPI release, addition of air as a media, and conversion to a new database structure. The previous RAIS PRG calculator presented PRGs for radionuclides and chemcials together. Recent development of chemical and radionuclide exposure equations has necessitated that the RAIS separate the chemicals and the radionuclides. To calculate PRGs for chemicals, use the RAIS Preliminary Remediation Goals (PRGs) for Chemicals calculator.

Currently the agricultural equations for the RAIS chemical and radionuclide PRG calculators are identical. The EPA's Preliminary Remediation Goals for Radionuclide Calculator offers more biota choices but with a different plant/soil/water uptake method. The EPA's resident soil equation includes ingestion of produce and the RAIS radionuclide equation does not.

1. Introduction

The purpose of this calculator is to provide a PRG calculation tool to assist risk assessors, remedial project managers, and others involved with risk assessment and decision-making in developing PRGs. This database is based on Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part B, Development of Risk-based Preliminary Remediation Goals) (RAGs Part B). RAGs Part B provides guidance on calculating risk-based PRGs. Initially used at the scoping phase of a project using readily available information, risk-based PRGs may be modified based on site-specific data gathered during the RI/FS study. PRG development and screening should assist staff in streamlining the consideration of remedial alternatives.

The recommended approach for developing remediation goals is to identify PRGs at scoping, modify them as needed at the end of the RI or during the FS based on site-specific information from the baseline risk assessment, and ultimately select remediation levels in the Record of Decision (ROD). In order to set radionuclide-specific PRGs in a site-specific context, however, assessors must answer fundamental questions about the site. Information on the radionuclides that are present onsite, the specific contaminated media, land-use assumptions, and the exposure assumptions behind pathways of individual exposure is necessary in order to develop radionuclide-specific PRGs. The PRG calculator provides the ability to modify the standard default PRG exposure parameters to calculate site-specific PRGs.

This database tool presents standardized risk-based PRGs and variable risk-based PRG calculation equations for radioactive contaminants. Ecological effects are not considered in the calculator for radionuclides PRGs.

Non-carcinogenic effects are not considered for radionuclide analytes, except for uranium for which both carcinogenic and non-carcinogenic effects are considered. To determine PRGs for the chemical toxicity of uranium, and for other chemicals, go to the RAIS Preliminary Remediation Goals (PRGs) for Chemicals website.

The standardized PRGs are based on default exposure parameters and incorporate exposure factors that present RME conditions. This database tool presents PRGs in both activity and mass units. Once this database tool is used to retrieve standard PRGs or calculate site-specific PRGs, it is important to clearly demonstrate the equations and exposure parameters used in the calculations. Discussion of the assumptions that go into the PRGs calculated should be included in the document where the PRGs are presented, such as a Remedial Investigation (RI) Report or Feasibility Study.

This website combines current EPA SFs with “standard” exposure factors to estimate contaminant concentrations in environmental media (air, soil, biota and water) that are protective of humans (including sensitive groups) over a lifetime. Sufficient knowledge about a given site may warrant the use of site-specific assumptions, which may differ from the defaults. Exceeding a PRG usually suggests that further evaluation of the potential risks is appropriate. The PRG concentrations presented on this website can be used to screen pollutants in environmental media, trigger further investigation, and provide initial cleanup goals, if applicable. PRGs should be applied in accordance with guidance from EPA Regions.

2. Understanding the PRG Website

2.1 General Considerations

PRGs are isotope concentrations that correspond to certain levels of risk in air, soil, water and biota. Slope factors (SFs) for a given radionuclide represent the risk equivalent per unit intake (i.e. , ingestion or inhalation) or external exposure of that radionuclide. In risk assessments these SFs are used in calculations with radionuclide concentrations and exposure assumptions to estimate cancer risk from exposure to radioactive contamination. The calculations may be rearranged to generate PRGs for a specified level of risk. SFs may be specified for specific body organs or tissues of interest, or as a weighted sum of individual organ dose, termed the effective dose equivalent. These SFs may be multiplied by the total activity of each radionuclide inhaled or ingested per year, or the external exposure concentration to which a receptor may be exposed, to estimate the risk to the receptor. Cancer slope factors used are from HEAST.

The PRGs are generated with standard exposure route equations using EPA SFs and exposure parameters.

2.2 Slope Factors (SFs)

EPA classifies all radionuclides as Group A carcinogens. The radionuclide table from HEAST 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. 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.

2.3 PRG in Context of Superfund Modeling Framework

This PRG calculator focuses on the application of generic and simple site-specific approaches that are part of a larger framework for calculating concentration levels for complying with risk based criteria. Generic PRGs for a 1 × 10^-06 cancer risk standard are provided by running the PRG Search section of this calculator with the "Defaults" option.

PRGs are calculated from the same equations presented in the site-specific portion of the calculator, but are based on a number of default assumptions chosen to be protective of human health for most site conditions. Generic PRGs can be used in place of site-specific PRG levels; however, in general, they are expected to be more conservative than site-specific levels. The site manager should weigh the cost of collecting the data necessary to develop site-specific PRGs with the potential for deriving a higher PRG that provides an appropriate level of protection.

3. Using the PRG Calculator

The PRG calculator provides generic concentrations in the absence of site-specific exposure assessments. Screening 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 PRGs, 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:

• Are there potential ecological concerns?
• Is there potential for land use other than those listed in the PRG calculator (i.e. , residential and industrial)?
• Are there other likely human exposure pathways that were not considered in development of the PRGs?
• Are there unusual site conditions (e.g. large areas of contamination, high fugitive dust levels, potential for indoor air contamination)?

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

3.2 Radionuclide Background

Natural background radiation should be considered prior to applying PRGs 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

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

• Applying PRG levels to a site without adequately developing a conceptual site model that identifies relevant exposure pathways and exposure scenarios.
• Use of PRG levels as cleanup levels without the consideration of other relevant criteria such as ARARs.
• Use of PRG levels as cleanup levels without verifying numbers with a health physicist/risk assessor.
• Use of outdated PRG levels tables that have been superseded by more recent publications.
• Not considering the effects from the presence of multiple isotopes.

4. Technical Support Documentation

The PRGs consider human exposure to contaminated soils, water and biota. The equations and technical discussion are aimed at developing compliance levels for risk-based PRGs. The following text presents the land use equations and their exposure routes. Table 1 presents the definitions of the variables and their default values. Any alternative values or assumptions used in remedy evaluation or selection on a CERCLA site should be presented with supporting rationale in Administrative Records.

Users should note that if a route of exposure (e.g., ingesting produce in the residential soil exposure scenario) is considered to be unreasonable at their site, both currently and in the future, they may eliminate the route in the site-specific option by entering zero for the ingestion rate of that route.

4.1 Residential Soil

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

external exposure to ionizing radiation and

Total.

4.2 Outdoor Worker Soil

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

external exposure to ionizing radiation and

Total.

4.3 Excavation/Construction Outdoor Worker Soil

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

external exposure to ionizing radiation and

Total.

4.4 Indoor Worker Soil

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

external exposure to ionizing radiation and

Total.

4.5 Recreational Soil/Sediment

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

external exposure to ionizing radiation and

Total.

4.6 Tapwater

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

ingestion of water,

inhalation of volatiles and

Total.

4.7 Recreation Surface Water

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

ingestion of water

4.8 Ambient Air

4.8.1 Resident

The ambient air land use equation, presented here, contains the following exposure route:

inhalation

4.8.2 Outdoor Worker

The ambient air land use equation, presented here, contains the following exposure route:

inhalation

4.8.3 Indoor Worker

The ambient air land use equation, presented here, contains the following exposure route:

inhalation

4.8.4 Excavation/Construction Worker

The ambient air land use equation, presented here, contains the following exposure route:

inhalation

4.9 Ingestion of Fish

4.9.1 Concentration in Fish

The ingestion of fish equation, presented here, contains the following exposure route:

consumption of fish.

4.9.2 Concentration in Surface Water

The ingestion of fish equation, presented here, contains the following exposure route:

consumption of fish.

Note: the consumption rate for fish is not age adjusted for this land use.

4.10 Agriculture

4.10.1 Concentration in Fruit and Vegetables

The ingestion of fruits and vegetables equation, presented here, contains the following exposure route:

consumption of fruits and vegetables.

4.10.2 Back-calculated Concentration in Water Only for Fruits and Vegetables

consumption of fruits and vegetables.

4.10.3 Back-calculated Concentration in Soil Only for Fruits and Vegetables

consumption of fruits and vegetables.

4.10.4 Back-calculated Concentration in Soil and Water for Fruits and Vegetables

consumption of fruits and vegetables.

4.10.5 Concentration in Milk

consumption of milk.

4.10.6 Back-calculated Concentration in Water Only for Milk

consumption of milk.

4.10.7 Back-calculated Concentration in Soil Only for Milk

consumption of milk.

4.10.8 Back-calculated Concentration in Soil and Water for Milk

consumption of milk.

4.10.9 Concentration in Beef

The ingestion of beef equation, presented here, contains the following exposure route:

consumption of beef.

4.10.10 Back-calculated Concentration in Water Only for Beef

consumption of beef.

4.10.11 Back-calculated Concentration in Soil Only for Beef

consumption of beef.

4.10.12 Back-calculated Concentration in Soil and Water for Beef

consumption of beef.

4.11 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).

4.11.1 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 ug/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 Table 1.

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 PRG 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.

4.11.2 Radionuclide Decay Constant

The residential soil, outdoor worker, indoor worker, and agricultural soil land uses (all the soil related land uses) have a decay constant term which is based on the halflife of the isotope (λ). λ = Decay constant (0.693/halflife) yr-1. The intention of this term is to make realistic PRGs 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-214 and 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. The term (1 - e^-λt) takes into account the number of halflives that will occur within the ED to calculate an appropriate value. Definitions of the input variables are in Table 1.

4.11.3 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.

Table 1. Standard Default Factors

Symbol	Definition (units)	Default	Reference
PRGs
PRGres-sol-rad-ing	Resident Soil Radionuclide Ingestion (mg/kg)	Contaminant-specific	Determined in this calculator
PRGres-sol-rad-inh	Resident Soil Radionuclide Inhalation (mg/kg)	Contaminant-specific	Determined in this calculator
PRGres-sol-rad-ext	Resident Soil Radionuclide External (mg/kg)	Contaminant-specific	Determined in this calculator
PRGres-sol-rad-tot	Resident Soil Radionuclide Total (mg/kg)	Contaminant-specific	Determined in this calculator
PRGow-sol-rad-ing	Outdoor Worker Soil Radionuclide Ingestion (mg/kg)	Contaminant-specific	Determined in this calculator
PRGow-sol-rad-inh	Outdoor Worker Soil Radionuclide Inhalation (mg/kg)	Contaminant-specific	Determined in this calculator
PRGow-sol-rad-ext	Outdoor Worker Soil Radionuclide External (mg/kg)	Contaminant-specific	Determined in this calculator
PRGow-sol-rad-tot	Outdoor Worker Soil Radionuclide Total (mg/kg)	Contaminant-specific	Determined in this calculator
PRGew-sol-rad-ing	Excavation/Construction Worker Soil Radionuclide Ingestion (mg/kg)	Contaminant-specific	Determined in this calculator
PRGew-sol-rad-inh	Excavation/Construction Worker Soil Radionuclide Inhalation (mg/kg)	Contaminant-specific	Determined in this calculator
PRGew-sol-rad-ext	Excavation/Construction Worker Soil Radionuclide External (mg/kg)	Contaminant-specific	Determined in this calculator
PRGew-sol-rad-tot	Excavation/Construction Worker Soil Radionuclide Total (mg/kg)	Contaminant-specific	Determined in this calculator
PRGiw-rad-ing	Indoor Worker Soil Radionuclide Ingestion (mg/kg)	Contaminant-specific	Determined in this calculator
PRGiw-rad-inh	Indoor Worker Soil Radionuclide Inhalation (mg/kg)	Contaminant-specific	Determined in this calculator
PRGiw-sol-rad-ext	Indoor Worker Soil Radionuclide External (mg/kg)	Contaminant-specific	Determined in this calculator
PRGiw-rad-tot	Indoor Worker Soil Radionuclide Total (mg/kg)	Contaminant-specific	Determined in this calculator
PRGrec-sol-rad-ing	Recreation Soil Radionuclide Ingestion (mg/kg)	Contaminant-specific	Determined in this calculator
PRGrec-sol-rad-inh	Recreation Soil Radionuclide Inhalation (mg/kg)	Contaminant-specific	Determined in this calculator
PRGrec-sol-rad-ext	Recreation Soil Radionuclide External (mg/kg)	Contaminant-specific	Determined in this calculator
PRGrec-sol-rad-tot	Recreation Soil Radionuclide Total (mg/kg)	Contaminant-specific	Determined in this calculator
PRGwater-rad-ing	Resident Tapwater (Groundwater) Radionuclide Ingestion (ug/L)	Contaminant-specific	Determined in this calculator
PRGwater-rad-inh	Resident Tapwater (Groundwater) Radionuclide Inhalation (ug/L)	Contaminant-specific	Determined in this calculator
PRGwater-rad-tot	Resident Tapwater (Groundwater) Radionuclide Total (ug/L)	Contaminant-specific	Determined in this calculator
PRGrec-water-rad-ing	Recreation Surface Water Radionuclide Ingestion (ug/L)	Contaminant-specific	Determined in this calculator
PRGres-air-rad	Resident Air Radionuclide (ug/m3)	Contaminant-specific	Determined in this calculator
PRGow-air-rad	Outdoor Worker Air Radionuclide (ug/m3)	Contaminant-specific	Determined in this calculator
PRGiw-air-rad	Indoor Worker Air Radionuclide (ug/m3)	Contaminant-specific	Determined in this calculator
PRGew-air-rad	Excavation/Construction Worker Air Radionuclide (ug/m3)	Contaminant-specific	Determined in this calculator
PRGres-fsh-rad-ing	Resident Fish Radionuclide (mg/kg)	Contaminant-specific	Determined in this calculator
PRGres-fshw-rad-ing	Resident Surface Water Fish Radionuclide (mg/kg)	Contaminant-specific	Determined in this calculator
PRGag-prod-rad-ing	Agriculture Fruits and Vegetables Radionuclide Ingestion	Contaminant-specific	Determined in this calculator
PRGw-ag-prod-rad-ing	Agriculture Fruits and Vegetables Radionuclide Back-calculated Concentration in Water Ingestion	Contaminant-specific	Determined in this calculator
PRGs-ag-prod-rad-ing	Agriculture Fruits and Vegetables Radionuclide Back-calculated Concentration in Soil Ingestion	Contaminant-specific	Determined in this calculator
PRGsw-ag-prod-rad-ing	Agriculture Fruits and Vegetables Radionuclide Back-calculated Concentration in Soil and Water Ingestion	Contaminant-specific	Determined in this calculator
PRGag-milk-rad-ing	Agriculture Milk Radionuclide Ingestion	Contaminant-specific	Determined in this calculator
PRGw-ag-milk-rad-ing	Agriculture Milk Radionuclide Back-calculated Concentration in Water Ingestion	Contaminant-specific	Determined in this calculator
PRGs-ag-milk-rad-ing	Agriculture Milk Radionuclide Back-calculated Concentration in Soil Ingestion	Contaminant-specific	Determined in this calculator
PRGsw-ag-milk-rad-ing	Agriculture Milk Radionuclide Back-calculated Concentration in Soil and Water Ingestion	Contaminant-specific	Determined in this calculator
PRGag-beef-rad-ing	Agriculture Beef Radionuclide Ingestion	Contaminant-specific	Determined in this calculator
PRGw-ag-beef-rad-ing	Agriculture Beef Radionuclide Back-calculated Concentration in Water Ingestion	Contaminant-specific	Determined in this calculator
PRGs-ag-beef-rad-ing	Agriculture Beef Radionuclide Back-calculated Concentration in Soil Ingestion	Contaminant-specific	Determined in this calculator
PRGsw-ag-beef-rad-ing	Agriculture Beef Radionuclide Back-calculated Concentration in Soil and Water Ingestion	Contaminant-specific	Determined in this calculator
Slope Factors
SFs	Ingestion Slope Factor - soil (risk/pCi)	contaminant-specific	HEAST
SFf	Ingestion Slope Factor - food (risk/pCi)	contaminant-specific	HEAST
SFw	Ingestion Slope Factor - water (risk/pCi)	contaminant-specific	HEAST
SFi	Slope Factor - inhalation (risk/pCi)	contaminant-specific	HEAST
SFX	Slope Factor - external exposure (risk/yr per pCi/g)	contaminant-specific	HEAST
Dose and Decay Constant Variables
TR	Target Risk	1 × 10-06
tres	Time - resident (years)	30	U.S. EPA 1991a (pg. 15)
trec	Time - recreation (years)	30	U.S. EPA 1991a (pg. 15)
tow	Time - outdoor worker (years)	25	U.S. EPA 1991a (pg. 15)
tiw	Time - indoor worker (years)	25	U.S. EPA 1991a (pg. 15)
tew	Time - excavation/construction worker (years)	25	U.S. EPA 1991a (pg. 15)
tag	Time - Agriculture (years)	30	U.S. EPA 1991a (pg. 15)
λ	Decay Constant	= 0.693/halflife	Developed for Radionuclide Soil Screening calculator
Miscellaneous Variables
DFi	Dilution Factor - indoor (unitless)	0.4	U.S. EPA 2000a. (pg. 2-20). U.S. EPA 2000b. (pg. 2-13)
ACF	Area Correction Factor (unitless)	0.9	U.S. EPA 2000a. (pg. 2-22). U.S. EPA 2000b. (pg. 5-1)
GSF	Gamma Shielding Factor (unitless)	0.4	U.S. EPA 2000a. (pg. 2-22). U.S. EPA 2000b. (pg. 2-18)
BCF	Fish Bioconcentration Factor (L/kg)	Contaminant-specific
K	Andelman Volatilization Factor (L/m3)	0.5	U.S. EPA 1991b (pg. 20)
CFp	Fraction of Produce Consumed that is Contaminated	1	U.S. EPA 1998
CFm	Fraction of Milk Consumed that is Contaminated	1	U.S. EPA 1998
CFp	Fraction of Beef Consumed that is Contaminated	1	U.S. EPA 1998
Inhalation, Ingestion, and Consumption Rates
IRSc	Resident Soil Ingestion Rate - Child (mg/day)	200	U.S. EPA 1991a (pg. 15)
IRSa	Resident Soil Ingestion Rate - Adult (mg/day)	100	U.S. EPA 1991a (pg. 15)
IFSadj	Resident Soil Ingestion Rate - Age-adjusted (mg/day)	120	Calculated using the age-adjusted intake factors equation
IFAadj	Inhalation Rate -resident -age-adjusted (m3/day)	18	Calculated using the age adjusted intake factors equation
IRAa	Inhalation Rate - adult (m3/day)	20	U.S. EPA 1991a (pg. 15)
IRAc	Inhalation Rate - child (m3/day)	10	U.S. EPA 1997a (pg. 5-11)
IRAiw	Inhalation Rate - indoor worker (m3/day; based on a rate of 2.5m3/hr for 24hr)	60	U.S. EPA 1997a (pg. 5-11)
IRAow	Inhalation Rate - outdoor worker (m3/day; based on a rate of 2.5m3/hr for 24hr)	60	U.S. EPA 1997a (pg. 5-11)
IRAew	Inhalation Rate - excavation/construction worker (m3/day; based on a rate of 2.5m3/hr for 24hr)	60	U.S. EPA 1997a (pg. 5-11)
IRWc	Drinking Water Ingestion Rate - Child (L/day)	1	U.S. EPA 1989 (Exhibit 6-11)
IRWa	Drinking Water Ingestion Rate - Adult (L/day)	2	U.S. EPA 1989 (Exhibit 6-11)
IFWadj	Drinking Water Ingestion Rate - Age-adjusted (L/day)	1.8	Calculated using the age-adjusted intake factors equation
IFWrec	Recreation Water Ingestion Rate (L/hr)	0.05	U.S. EPA Region 4
IRFa	Fish Ingestion Rate (g/day)	54	U.S. EPA 1991a (pg. 15)
IRow	Soil Ingestion Rate - outdoor worker (mg/day)	100	U.S. EPA 2001 (pg. 4-3)
IRiw	Soil Ingestion Rate - indoor worker (mg/day)	50	U.S. EPA 1991a (pg. 15)
IRew	Soil Ingestion Rate - excavation/construction worker (mg/day)	330	U.S. EPA 2002
IRPfr-c	Produce Ingestion Rate - Fruit - Child (mg/day)	14.8	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPfr-a	Produce Ingestion Rate - Fruit - Adult (mg/day)	56.2	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPfr-adj	Produce Ingestion Rate - Fruit - Age-adjusted (mg/day)	47.92	Calculated using the aged adjusted intake factors equation
IRPvg-c	Produce Ingestion Rate - Vegetables - Child (mg/day)	10.4	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPvg-a	Produce Ingestion Rate - Vegetables - Adult (mg/day)	28.5	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPvg-adj	Produce Ingestion Rate - Vegetables - Age-adjusted (mg/day)	24.88	Calculated using the aged adjusted intake factors equation
IRMc	Milk Ingestion Rate - Child (mg/day)	265	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRMa	Milk Ingestion Rate - Adult (mg/day)	615	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRMadj	Milk Ingestion Rate - Age-adjusted (mg/day)	545	Calculated using the aged adjusted intake factors equation
IRBc	Beef Ingestion Rate - Child (mg/day)	12.9	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRBa	Beef Ingestion Rate - Adult (mg/day)	138	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRBadj	Beef Ingestion Rate - Age-adjusted (mg/day)	112.98	Calculated using the aged adjusted intake factors equation
Irrrup	root uptake from irrigation multiplier (L/kg)	contaminant-specific	Calculated
Irrres	resuspension from irrigation multiplier (L/kg)	contaminant-specific	Calculated
Irrdep	aerial deposition from irrigation multiplier (L/kg)	contaminant-specific	Calculated
Rupp	dry root uptake for pasture multiplier (unitless)	=BVdry
Rupv	wet root uptake for vegetables multiplier (unitless)	=BVwet
Qp-b	Beef Fodder Intake Rate (kg/day)	11.77	U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
Qp-m	Dairy Fodder Intake Rate (kg/day)	16.9	U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
Qw-dairy	Dairy Water Intake Rate (kg/day)	92	U.S. EPA 1999a (pg 10-23).
Qw-beef	Beef Water Intake Rate (kg/day)	53	U.S. EPA 1999a (pg 10-23).
Qs-m	Dairy Soil Intake Rate (kg/day)	0.41	U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
Qs-b	Beef Soil Intake Rate (kg/day)	0.39	U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
fp-b	fraction of year animal is on site (unitless)	1
fp-m	fraction of year animal is on site (unitless)	1
fs-b	fraction of animal's food is from site (unitless)	1
fs-m	fraction of animal's food is from site (unitless)	1
Fm	Milk Transfer Factor (day/kg)	Contaminant-specific	ANL. 1993. NCRP 1996.
Fb	Beef Transfer Factor (day/kg)	Contaminant-specific	ANL. 1993. NCRP 1996.
Ir	Irrigation rate (L/m2-day)	3.62	Personnal communication
F	irrigation period (unitless)	0.25 (based on 3 months per year)	Personnal communication
λB	effective rate for removal (1/day)	λi + λHL	NCRP 1989
λE	decay for removal on produce (1/day)	λi + (0.693/tw)	NCRP 1989
λHL	soil leaching rate (1/day)	0.000027	NCRP 1989
λi	decay (1/day)	0.693/TR - radionuclides, 0 - non-radionuclides	NCRP 1989
tW	weathering half -life (day)	14	NCRP 1989
TR	half-life (days)	Contaminant-specific
MLFpasture	Pasture plant mass loading factor (unitless)	0.25	Hinton, T. G. 1992
MLFprodude	Produce plant mass loading factor (unitless)	0.26	Pinder, J. E., and K. W. McLeod. 1989
tb	long term deposition and buildup (day)	10950	NCRP 1985
tv	above ground exposure time (day)	60	NCRP 1985
If	interception fraction (unitless)	0.42	Miller, C. W. 1980
Yv	plant yield (wet) (kg/m2)	2	NCRP 1985
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
T	translocation factor (unitless)	1	NCRP 1984
Res	= MLF (produce or pasture)
Exposure Frequency, Exposure Duration, and Exposure Time Variables
EFr	Exposure Frequency - residential (days/yr)	350	U.S. EPA 1991a (pg. 15)
EFrec	Exposure Frequency - recreation (days/yr)	75	U.S. EPA 1991a (pg. 15)
EFrec-w	Water Exposure Frequency - recreation (days/yr)	45	U.S. EPA 1991a (pg. 15)
EFag	Exposure Frequency - agricultural (days/yr)	350	U.S. EPA 1991a (pg. 15)
EFiw	Exposure Frequency - indoor worker (days/yr)	250	U.S. EPA 1991a (pg. 15)
EFow	Exposure Frequency - outdoor worker (days/yr)	225	U.S. EPA 1991a (pg. 15)
EFew	Exposure Frequency - excavation/construction worker (days/yr)	20	one month of the worker year, or approximately 20 days per year
EDr	Exposure Duration - resident (yr)	30	U.S. EPA 1991a (pg. 15)
EDag	Exposure Duration - agricultural (yr)	40	U.S. EPA 1994a U.S. EPA 1998 (Table C-1-7)
EDc	Exposure Duration - child resident (yr)	6	U.S. EPA 1991a (pg. 15)
EDrec	Exposure Duration - recreation (yr)	30	U.S. EPA 1991a (pg. 15)
EDow	Exposure Duration - outdoor worker (yr)	25	U.S. EPA 1991a (pg. 15)
EDiw	Exposure Duration - indoor worker(yr)	25	U.S. EPA 1991a (pg. 15)
EDew	Exposure Duration - excavation/construction worker (yr)	1	U.S. EPA 1991a (pg. 15)
ETiwi	Exposure Time - indoor worker (indoor) (hr/hr)	0.33	Eight Hours per 24 hr Day
ETiwo	Exposure Time - indoor worker (outdoor) (hr/hr)	0
ETowi	Exposure Time - outdoor worker (indoor) (hr/hr)	0
ETowo	Exposure Time - outdoor worker (outdoor) (hr/hr)	0.33	Eight Hours per 24 hr Day
ETewi	Exposure Time - excavation/construction worker (indoor) (hr/hr)	0
ETewo	Exposure Time - excavation/construction worker (outdoor) (hr/hr)	0.33	Eight Hours per 24 hr Day
ETres	Exposure Time - resident (hr/day)	24
ETri	Exposure Time - resident (indoor) (hr/hr)	0.683	U.S. EPA 2000a. (pg. 2-22). U.S. EPA 2000b. (pg. 2-17). U.S. EPA 1997a (Table 15-131)
ETro	Exposure Time - resident (outdoor) (hr/hr)	0.073	U.S. EPA 2000a. (pg. 2-22). U.S. EPA 2000b. (pg. 2-17). U.S. EPA 1997a (Table 15-132)
ETrec	Exposure Time - recreation (hr/day)	1
Particulate Emission Factor Variables
PEF	Particulate Emission Factor - Minneapolis (m3/kg)	1.36 x 109	U.S. EPA 1996a (pg. 23), U.S. EPA 1996b (pg. 31)
Q/C	Inverse of the Mean Concentration at the Center of a 0.5-Acre-Square Source (g/m2-s per kg/m3)	93.77	U.S. EPA 1996a (pg. 23), U.S. EPA 1996b (pg. 31)
V	(fraction of vegetative cover) unitless	0.5	U.S. EPA 1999b, U.S. EPA 1996a (pg. 23), U.S. EPA 1996b (pg. 31)
Um	mean annual wind speed) m/s	4.69	U.S. EPA 1999b, U.S. EPA 1996a (pg. 23), U.S. EPA 1996b (pg. 31)
Ut	equivalent threshold value of wind speed at 7m) m/s	11.32	U.S. EPA 1991b, U.S. EPA 1996a (pg. 23), U.S. EPA 1996b (pg. 32)
F(x)	function dependent on Um/Ut) unitless	0.194	U.S. EPA 1991b, U.S. EPA 1996a (pg. 23), U.S. EPA 1996b (pg. 31)

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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

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.

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

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. " USDA assumes a pig consumes 1/4 to 1/3 gallon of water for every pound of dry feed. The midpoint of this range (7/24 gallons of water) was used with the default dry feed (4.7 kg) to come up with 11.4 gallons 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

U.S. EPA. 1988. Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion. Federal Guidance Report No. 11. Office of Radiation Programs, Washington, DC. EPA-520/1-88-020. http://homer.hsr.ornl.gov/vlab/FedGR11.html

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://homer.hsr.ornl.gov/VLAB/FedGR12.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.

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. http://www.epa.gov/radiation/docs/cleanup/402-r-96-011a.html 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.

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. 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 http://www.epa.gov/epaoswer/hazwaste/combust/risk.htm

U.S. EPA. 1999a. Data Collection for the Hazardous Waste Identification Rule. Office of Solid Waste, Washington, DC. http://www.epa.gov/epaoswer/hazwaste/id/hwirwste/risk.htm

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.

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/

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

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.