Note

The RAIS presents this updated risk calculator in response to the following: incorporating RAGS Part Edermal guidance, incorporating chemical-specific parameters from the lastest EPIrelease, addition of air as a media, addition of ATSDR toxicity values, addition of California EPA toxicity values and conversion to a new database structure. The previous RAIS risk calculator presented risks 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 risks for radionuclides, use the RAIS Risk Exposure Models for Radionuclides calculator.

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

1. Introduction

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 chemical-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" http://www.epa.gov/superfund/programs/risk/ecorisk/ecorisk.htmcontains an eight step process for using benchmarks for ecological effects in the remedy selection process. For ecological effects use the Ecological Benchmarktool on this site.

2. Understanding the Calculator Results

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 chemicals 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 [mg/kg-day; risk/pCi]
SF = slope factor, expressed in [(mg/kg-day)^-1; pCi/risk]

The basic equation for calculating systemic toxicity (i.e., noncarcinogenic hazard) is:

Noncancer Hazard Quotient = CDI/RfD

where:

CDI = chronic daily intake for the toxicant, expressed in mg/kg-day
RfD = chronic reference dose for the toxicant, expressed in mg/kg-day

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 (1996and 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 Toxicity Values

In a 2003 memo, EPA Superfund revised its hierarchy of human health toxicity values, providing three tiers of toxicity values. Three tier 3 sources were identified in that guidance, but it was acknowledged that additional tier 3 sources may exist. The 2003 guidance did not attempt to rank or put the identified tier 3 sources into a hierarchy of their own; however, when developing this calculator for the RAIS, a hierarchy was needed for all sources. The toxicity values used in this calculator are consistent with the 2003 guidance. Toxicity values from the following sources, in the order in which they are presented below, are used as the defaults in this calculator.

EPA’s Integrated Risk Information System (IRIS)

Federal Register. Thursday December 7, 2000. Part II, Environmental Protection Agency. 40 CFR Parts 9, 141, and 142 - National Primary Drinking Water Regulations; Radionuclides; Final Rule. p 76713.

World Health Organization toxicity equivalence factors (TEFs).  Van den Berg et al. (2006)presents the WHO 2005 TEFs for carcinogenic dioxins and furans and polychlorinated biphenyls. Ahlborg et al. (1994) presents the WHO 1994 TEFs for carcinogenic polychlorinated biphenyls 170 and 180 in Toxic equivalency factors for dioxin-like PCBs: Report on a WHO-ECEH and IPCS consultation, December 1993. Chemosphere, Vol. 28, No. 6, 1049-1067. Polycyclic aromatic hydrocarbon TEFs are presented in Provisional Guidance for Quantitative Risk Assessment of Polycyclic Aromatic Hydrocarbons.

The Provisional values (PROV) derived by EPA’s Superfund Health Risk Technical Support Center (STSC) for the EPA Superfund program.

The California Environmental Protection Agency/Office of Environmental Health Hazard Assessment’s toxicity values- http://www.oehha.ca.gov/risk/ChemicalDB/index.asp

The Agency for Toxic Substances and Disease Registry (ATSDR) minimal risk levels (MRLs)- http://www.atsdr.cdc.gov/mrls/index.html

Other sources such as NCEA that were provided to the RAIS for use on the Oak Ridge Reservation.

The EPA Superfund program’s Health Effects Assessment Summary. (Note that the HEASTwebsite is not open to users outside of EPA, but access can be obtained for use on Superfund sites by contacting Dave Crawford at Crawford.Dave@epa.gov).

Values withdrawn from IRIS or HEAST.

When using toxicity values other than tier 1, users are encouraged to carefully review the basis for the value, and to document its use in decision documentation on a site.

2.3.1 Noncancer Toxicity Values - Reference Doses

Noncancer toxicity values are reference doses and reference concentrations. The current, or recently completed, EPA toxicity assessments used in these screening tables (IRIS and PROV) define a reference dose, or RfD, as an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be derived from a NOAEL, LOAEL, or benchmark dose, or using categorical regression, with uncertainty factors generally applied to reflect limitations of the data used. RfDs are generally the toxicity value used most often in evaluating noncancer health effects at Superfund sites. Various types of RfDs are available depending on the exposure route (oral or inhalation), the critical effect (developmental or other), and the length of exposure being evaluated (chronic or subchronic). Some of the risks in this calculator also use Agency for Toxic Substances and Disease Registry (ATSDR) chronic oral minimal risk levels (MRLs) as oral chronic RfDs. The HEAST RfDs used in these risks were based upon then current EPA toxicity methodologies, but did not use the more recent benchmark dose or categorical regression methodologies.

2.3.1.1 Chronic Oral Reference Doses

A chronic oral RfD is defined as an estimate (with uncertainty spanning perhaps an order of magnitude or greater) of a daily oral exposure level for the human population, including sensitive subpopulations, that is likely to be without an appreciable risk of deleterious effects during a lifetime. Chronic oral RfDs are specifically developed to be protective for long-term exposure to a compound. As a guideline for Superfund program risk assessments, chronic oral RfDs generally should be used to evaluate the potential noncarcinogenic effects associated with exposure periods greater than 7 years (approximately 10 percent of a human lifetime). Chronic oral reference doses and ATSDR chronic oral MRLs are expressed in units of mg/kg-day.

2.3.1.2 Subchronic Oral Reference Doses

EPA has begun developing subchronic oral RfDs, which are useful for characterizing potential noncarcinogenic effects associated with shorter-term exposures by the oral route. As a guideline for Superfund program risk assessments, subchronic oral RfDs should generally be used to evaluate the potential noncarcinogenic effects of exposure periods between two weeks and seven years. Such short-term exposures can result when a particular activity is performed for a limited number of years or when a chemical with a short half-life degrades to negligible concentrations within several months. Subchronic oral reference doses and ATSDR intermediate oral MRLs are expressed in units of mg/kg-day.

2.3.2 Reference Concentrations - Reference Concentrations

The current, or recently completed, EPA toxicity assessments used in these screening tables (IRIS and PPRTV assessments) define a reference concentration (RfC) as an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be derived from a NOAEL, LOAEL, or benchmark concentration, or using categorical regression with uncertainty factors generally applied to reflect limitations of the data used. Various types of RfCs are available depending on the exposure route (oral or inhalation), the critical effect (developmental or other), and the length of exposure being evaluated (chronic or subchronic). These screening tables also use ATSDR chronic inhalation MRLs as chronic RfCa, intermediate inhalation MRLs as subchronic RfCa and California Environmental Protection Agency (chronic) Reference Exposure Levels (RELs) as chronic RfCs. These screening tables may also use some RfCs from EPA’s HEAST tables.

2.3.2.1 Chronic Inhalation Reference Concentrations

The chronic inhalation reference concentration is generally used for continuous or near continuous inhalation exposures that occur for 7 years or more. EPA chronic inhalation reference concentrations are expressed in units of mg/m³. Cal EPA RELs are presented in µg/m³and have been converted to mg/m³for use in these screening tables. Some ATSDR inhalation MRLs are derived in parts per million (ppm) and some in mg/m³. For use in this table, all were converted into mg/m³.

2.3.2.2 Subchronic Inhalation Reference Concentrations

The subchronic inhalation reference concentration is generally used for inhalation exposures that are between 2 weeks and 7 years. Subchronic inhalation reference concentrations are expressed in units of mg/m³. As noted above, some ATSDR (intermediate) inhalation MRLs were derived in ppm and converted for use in this table into mg/m³.

2.3.3 Cancer Toxicity Values

Slope factors and unit risk values are used to assess cancer risk. A slope factor and the accompanying weight-of-evidence determination are the toxicity data most commonly used to evaluate potential human carcinogenic risks. Generally, the slope factor is a plausible upper-bound estimate of the probability of a response per unit intake of a chemical over a lifetime. The slope factor is used in risk assessments to estimate an upper-bound lifetime probability of an individual developing cancer as a result of exposure to a particular level of a potential carcinogen. Slope factors should always be accompanied by the weight-of-evidence classification to indicate the strength of the evidence that the agent is a human carcinogen. The ATSDR does not derive cancer toxicity values (e.g. slope factors or inhalation unit risks). Some slope factors used in these screening tables were derived by the California Environmental Protection Agency, whose methodologies are quite similar to those used by EPA’s IRIS and PPRTV assessments.

2.3.3.1 Oral Slope Factors

The oral slope factor evaluates the probability of an individual developing cancer from oral exposure to contaminant levels over a lifetime. Oral slope factors are expressed in units of (mg/kg-day)^-1

2.3.3.2 Inhalation Unit Risk

The IUR is defined as the upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 µg/m³in air. Inhalation unit risk toxicity values are expressed in units of (µg/m³)^-1.

2.3.4 Toxicity Equivalence Factors

Some chemicals are members of the same family and exhibit similar toxicological properties; however, they differ in the degree of toxicity. Therefore, a toxicity equivalence factor (TEF) must first be applied to adjust the measured concentrations to a toxicity equivalent concentration.

The following table contains the various dioxin-like toxicity equivalency factors for Dioxins, Furans and PCBs (Van den Berg et al. (2006)), which are the World Health Organization 2005 values.

* Di-ortho values come from Ahlborg, U.G., et al. (1994), which are the WHO 1994 values from Toxic equivalency factors for dioxin-like PCBs: Report on WHO-ECEH and IPCS consultation, December 1993 Chemosphere, Volume 28, Issue 6, March 1994, Pages 1049-1067.

Carcinogenic polycyclic aromatic hydrocarbons

Provisional Guidance for Quantitative Risk Assessment of Polycyclic Aromatic Hydrocarbons(EPA/600/R-93/089, July 1993), recommends that a toxicity equivalency factor (TEF) be used to convert concentrations of carcinogenic polycyclic aromatic hydrocarbons (cPAHs) to an equivalent concentration of benzo(a)pyrene when assessing the risks posed by these substances. These TEFs are based on the potency of each compound relative to that of benzo(a)pyrene. For the toxicity value database, these TEFs have been applied to the toxicity values. Although this is not in complete agreement with the direction in the aforementioned documents, this approach was used so that toxicity values could be generated for each cPAH. Additionally, it should be noted that computationally it makes little difference whether the TEFs are applied to the concentrations of cPAHs found in environmental samples or to the toxicity values as long as the TEFs are not applied to both. However, if the adjusted toxicity values are used, the user will need to sum the risks from all cPAHs as part of the risk assessment to derive a total risk from all cPAHs. A total risk from all cPAHs is what is derived when the TEFs are applied to the environmental concentrations of cPAHs and not to the toxicity values.

The following table presents the TEFs for cPAHs recommended in Provisional Guidance for Quantitative Risk Assessment of Polycyclic Aromatic Hydrocarbons.

Toxicity Equivalency Factors for Carcinogenic Polycyclic Aromatic Hydrocarbons

2.4 Chemical-specific Parameters

Several chemical specific parameters are needed for development of the SLs. Different hierarchies are used for organic and inorganic compounds.

2.4.1 Organic Compounds

1. Values were taken from http://www.epa.gov/opptintr/exposure/pubs/episuite.htm. These programs estimate various chemical-specific properties. The calculations for these SL tables use the experimental values for a property over the estimated values.

2. EPA Soil Screening Level (SSL) Exhibit C-1.

3. WATER8, which has been replaced with WATER9.

4. Syracuse Research Corporation (SRC). 2005. CHEMFATEDatabase. SRC. Syracuse, NY. Accessed July 2005.

5. Syracuse Research Corporation (SRC). 2005. PHYSPROPDatabase. SRC. Syracuse, NY. Accessed July 2005.

2.4.2 Inorganic Compounds

For unitless Henry's Law (ammonia, chlorine, cyanogen, cyanogen chloride, hydrogen cyanide only):

1. Syracuse Research Corporation (SRC). 2005. PHYSPROP Database. SRC. Syracuse, NY.
   (http://www.syrres.com/esc/physdemo.htm).

2. Yaws' Handbook of Thermodynamic and Physical Properties of Chemical Compounds. Knovel, 2003.
   (http://www.knovel.com).

For Kd (soil-water partition coefficient):

1. EPA Soil Screening Level (SSL) Table C.4 (http://www.epa.gov/superfund/health/conmedia/soil/index.htm).

2. Baes, C.F. 1984. Oak Ridge National Laboratory. A Review and Analysis of Parameters for Assessing Transport of Environmentally Released Radionuclides through Agriculture. http://homer.ornl.gov/baes/documents/ornl5786.html. Values are also found in Superfund Chemical Data Matrix (SCDM)
   (http://www.epa.gov/superfund/sites/npl/hrsres/tools/scdm.htm).

For molecular weights:

1. EPI (http://www.epa.gov/oppt/exposure/pubs/episuite.htm)

2. Syracuse Research Corporation (SRC). 2005. PHYSPROP Database. SRC. Syracuse, NY.
   ( http://www.syrres.com/esc/physdemo.htm).

For Vapor Pressure:

1. NIOSH Pocket Guide to Chemical Hazards (NPG), NIOSH Publication No. 97-140, February 2004.
   (http://www.cdc.gov/niosh/npg/npg.html).

2. 2) Syracuse Research Corporation (SRC). 2005. CHEMFATE Database. SRC. Syracuse, NY.
   ( http://www.syrres.com/esc/chemfate.htm).

3. Syracuse Research Corporation (SRC). 2005. PHYSPROP Database. SRC. Syracuse, NY.
   ( http://www.syrres.com/esc/physdemo.htm).

For diffusivity in air and water, if desired at all, for the gasses and mercuric compounds:

1. WATER 9, (EPA 2001). See section 4.9.2.

3. Using the Risk Calculator

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

• Prioritizing multiple sites or operable units or areas of concern within a facility or exposure units
• Setting risk-based detection limits for contaminants of potential concern (COPCs)
• Focusing future site investigation and risk assessment efforts
• Identifying contamination which may warrant cleanup
• Identifying sites, or portions of sites, which warrant no further action or investigation

Risks are provided for multiple exposure pathways and for chemicals with both carcinogenic and noncarcinogenic effects. Site specific risks can be calculated and may be appropriate based upon site specific considerations.

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 calculator. (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 risks 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 Superfund: Users Guide (EPA 1996) contains the steps for developing a CSM.

• Are there potential ecological concerns?
• Is there potential for land use other than those used in the PRG calculations (i.e., residential and commercial/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 risk equations may need to be adjusted to reflect the answers to these questions.

3.2 Background

Natural background concentrations should be considered prior to calculating risks. Background levels 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).

3.3 Potential Problems

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

• Applying risks to a site without adequately developing a conceptual site model that identifies relevant exposure pathways and exposure scenarios.
• Not considering the effects from the presence of multiple contaminants, where appropriate.
• Use of the risks without adequate consideration of the other NCP remedy selection criteria on CERCLA sites.
• Use of outdated equations or toxicity values.

4. Technical Support Documentation

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. Table 1presents 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.

4.1 Residential Soil

4.1.1 Noncancer

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.1.2 Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.1.3 Mutagenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.1.4 Vinyl Chloride - Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.2 Outdoor Worker Soil

4.2.1 Noncancer

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

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

dermal exposure.

4.2.2 Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

dermal exposure.

4.3 Excavation/Construction Outdoor Worker Soil

4.3.1 Noncancer

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

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

dermal exposure.

4.3.2 Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

dermal exposure.

4.4 Indoor Worker Soil

4.4.1 Noncancer

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

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

4.4.2 Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil, and

4.5 Recreational Soil

4.5.1 Noncancer

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.5.1 Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.5.3 Mutagenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.5.4 Vinyl Chloride - Carcinogenic

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

incidental ingestion of soil,

inhalation of particulates emitted from soil,

dermal contact with soil.

4.6 Tapwater

4.6.1 Noncarcinogenic

The tapwater CDI equations, presented here, contain the following exposure routes:

ingestion of water,

dermal contact with water and

inhalation of volatiles

4.6.2 Carcinogenic

The tapwater CDI equations, presented here, contain the following exposure routes:

ingestion of water,

dermal contact with water and

inhalation of volatiles

4.6.3 Mutagenic

The tapwater CDI equations, presented here, contain the following exposure routes:

ingestion of water,

dermal contact with water and

inhalation of volatiles

4.6.4 Vinyl Chloride - Carcinogenic

The tapwater CDI equations, presented here, contain the following exposure routes:

ingestion of water,

dermal contact with water and

inhalation of volatiles

4.7 Recreation Surface Water

4.7.1 Noncarcinogenic

The surface water CDI equations, presented here, contain the following exposure routes:

ingestion of water and

dermal contact with water

4.7.2 Carcinogenic

The surface water CDI equations, presented here, contain the following exposure routes:

ingestion of water and

dermal contact with water

4.8 Ambient Air

4.8.1 Resiedent

4.8.1.1 Noncarcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.1.2 Carcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.1.3 Mutagenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.1.4 Vinyl Chloride - Carcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.2 Outdoor Worker

4.8.2.1 Noncarcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.2.2 Carcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.3 Indoor Worker

4.8.3.1 Noncarcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.3.2 Carcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.8.4 Excavation/Construction Worker

4.8.4.1 Noncarcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.6.4.2 Carcinogenic

The Ambient air CDI equation, presented here, contains the following exposure routes:

inhalation of volatiles

4.9 Ingestion of Fish

4.9.1 Concentration in Fish

4.9.1.1 Noncarcinogenic

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

consumption of fish.

4.9.1.2 Carcinogenic

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

consumption of fish.

4.9.2 Concentration in Surface Water

4.9.2.1 Noncarcinogenic

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

consumption of fish.

4.9.2.2 Carcinogenic

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

4.10.1.1 Noncarcinogenic

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

consumption of fruits and vegetables.

4.10.1.2 Carcinogenic

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

4.10.2.1 Noncarcinogenic

consumption of fruits and vegetables.

4.10.2.2 Carcinogenic

consumption of fruits and vegetables.

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

4.10.3.1 Noncarcinogenic

consumption of fruits and vegetables.

4.10.3.2 Carcinogenic

consumption of fruits and vegetables.

4.10.4 Concentration in Milk

4.10.4.1 Noncarcinogenic

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

consumption of milk.

4.10.4.2 Carcinogenic

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

consumption of milk.

4.10.5 Back-calculated Concentration in Water Only for Milk

4.10.5.1 Noncarcinogenic

consumption of milk.

4.10.5.2 Carcinogenic

consumption of milk.

4.10.6 Back-calculated Concentration in Soil Only for Milk

4.10.6.1 Noncarcinogenic

consumption of milk.

4.10.6.2 Carcinogenic

consumption of milk.

4.10.7 Concentration in Beef

4.10.7.1 Noncarcinogenic

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

consumption of beef.

4.10.7.2 Carcinogenic

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

consumption of beef.

4.10.8 Back-calculated Concentration in Water Only for Beef

4.10.8.1 Noncarcinogenic

consumption of beef.

4.10.8.2 Carcinogenic

consumption of beef.

4.10.9 Back-calculated Concentration in Soil Only for Beef

4.10.9.1 Noncarcinogenic

consumption of beef.

4.10.9.2 Carcinogenic

consumption of beef.

4.11 Supporting Equations and Parameter Discussion

There are two inhalation variables in the above CDI equations that require further explanation: the particulate emission factor (PEF) and the volatilization factor (VF).

4.11.1 Particulate Emission Factor (PEF)

Inhalation of contaminants adsorbed to respirable particles (PM10) was assessed using a default PEF equal to 1.36 x 10⁹m³/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.

4.11.2 Volatilization Factor (VF)

The soil-to-air VF is used to define the relationship between the concentration of the contaminant in soil and the flux of the volatilized contaminant to air. VF is calculated from the equation below using chemical-specific properties and either site-measured or default values for soil moisture, dry bulk density, and fraction of organic carbon in soil. The Soil Screening Guidance: User's Guidedescribes how to develop site measured values for these parameters.

5. Special Considerations

Most of the risks are readily derived by referring to the above equations. However, there are some cases for which the standard equations do no apply and/or external adjustments to the equationss are not recommended. These special case chemicals are discussed below.

5.1 Cadmium

The equations for Cadmium are based on the oral RfD for water, which is slightly more conservative (by a factor of 2) than the RfD for food. However, reasonable arguments could be made for applying an RfD for food (instead of the oral RfD for water) for some media, such as soils.

5.2 Lead

Residential equations for Lead (Region 9 EPA and California EPA) are derived based on pharmacokinetic models. Both EPA’s Integrated Exposure Uptake Biokinetic (IEUBK) Model and California’s LeadSpread model are designed to predict the probable blood lead concentrations for children between six months and seven years of age who have been exposed to lead through various sources (air, water, soil, dust, diet and in utero contributions from the mother). Run in the reverse, these models also allow the user to calculate lead PRGs that are considered “acceptable” by EPA or the State of California.

For more information on EPA’s lead models and other lead-related topics, please go to:

http://www.epa.gov/oerrpage/superfund/health/contaminants/lead/index.htm.

For more information on California’s LeadSpread Model and Cal-Modified PRGs for lead, please go to:

http://www.dtsc.ca.gov/AssessingRisk/leadspread.cfm.

5.3 Manganese

The IRIS RfD (0.14 mg/kg-day) for manganese is from all sources, including diet. The author of the IRIS assessment for manganese recommended that the dietary contribution from the normal U.S. diet (an upper limit of 5 mg/day) be subtracted when evaluating non-food (e.g. drinking water or soil) exposures to manganese, leading to a RfD of 0.071 mg/kg-day for non-food items. The explanatory text in IRIS further recommends using a modifying factor of 3 when calculating risks associated with non-food sources due to a number of uncertainties that are discussed in the IRIS file for manganese, leading to a RfD of 0.024 mg/kg-day. For more information regarding the Manganese RfD, users are advised to contact the author of the IRIS assessment on Manganese.

5.4 One-hit Rule Equation

The linear risk equation (SF*CDI = risk) is valid only at low risk levels (below estimated risks of 0.01). For sites where chemical intakes 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 .

Table 1. Standard Default Factors

Symbol	Definition (units)	Default	Reference
CDIs
CDIres-sol-nc-ing	Resident Soil Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-sol-nc-der	Resident Soil Noncarcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-sol-nc-inh	Resident Soil Noncarcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIres-sol-ca-ing	Resident Soil Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-sol-ca-der	Resident Soil Carcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-sol-ca-inh	Resident Soil Carcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIres-sol-mu-ing	Resident Soil Mutagenic Ingestion (mg/kg-day)	Mutagen-specific	Determined in this calculator
CDIres-sol-mu-der	Resident Soil Mutagenic Dermal (mg/kg-day)	Mutagen-specific	Determined in this calculator
CDIres-sol-mu-inh	Resident Soil Mutagenic Inhalation (mg/m3)	Mutagen-specific	Determined in this calculator
CDIres-soil-ca-vc-ing	Resident Soil Carcinogenic Vinyl Chloride Ingestion (mg/kg-day)	Vinyl Chloride -specific	Determined in this calculator
CDIres-soil-ca-vc-der	Resident Soil Carcinogenic Vinyl Chloride Dermal (mg/kg-day)	Vinyl Chloride-specific	Determined in this calculator
CDIres-soil-ca-vc-inh	Resident Soil Carcinogenic Vinyl Chloride Inhalation (mg/m3)	Vinyl Chloride-specific	Determined in this calculator
CDIow-sol-nc-ing	Outdoor Worker Soil Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIow-sol-nc-der	Outdoor Worker Soil Noncarcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIow-sol-nc-inh	Outdoor Worker Soil Noncarcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIow-sol-ca-ing	Outdoor Worker Soil Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIow-sol-ca-der	Outdoor Worker Soil Carcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIow-sol-ca-inh	Outdoor Worker Soil Carcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIew-sol-nc-ing	Excavation/Construction Worker Soil Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIew-sol-nc-der	Excavation/Construction Worker Soil Noncarcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIew-sol-nc-inh	Excavation/Construction Worker Soil Noncarcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIew-sol-ca-ing	Excavation/Construction Worker Soil Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIew-sol-ca-der	Excavation/Construction Worker Soil Carcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIew-sol-ca-inh	Excavation/Construction Worker Soil Carcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIiw-nc-ing	Indoor Worker Soil Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIiw-nc-inh	Indoor Worker Soil Noncarcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIiw-ca-ing	Indoor Worker Soil Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIiw-ca-inh	Indoor Worker Soil Carcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIrec-sol-nc-ing	Recreation Soil Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-sol-nc-der	Recreation Soil Noncarcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-sol-nc-inh	Recreation Soil Noncarcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIrec-sol-ca-ing	Recreation Soil Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-sol-ca-der	Recreation Soil Carcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-sol-ca-inh	Recreation Soil Carcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIrec-sol-mu-ing	Recreation Soil Mutagenic Ingestion (mg/kg-day)	Mutagen-specific	Determined in this calculator
CDIrec-sol-mu-der	Recreation Soil Mutagenic Dermal (mg/kg-day)	Mutagen-specific	Determined in this calculator
CDIrec-sol-mu-inh	Recreation Soil Mutagenic Inhalation (mg/m3)	Mutagen-specific	Determined in this calculator
CDIrec-soil-ca-vc-ing	Recreation Soil Carcinogenic Vinyl Chloride Ingestion (mg/kg-day)	Vinyl Chloride -specific	Determined in this calculator
CDIrec-soil-ca-vc-der	Recreation Soil Carcinogenic Vinyl Chloride Dermal (mg/kg-day)	Vinyl Chloride-specific	Determined in this calculator
CDIrec-soil-ca-vc-inh	Recreation Soil Carcinogenic Vinyl Chloride Inhalation (mg/m3)	Vinyl Chloride-specific	Determined in this calculator
CDIwater-nc-ing	Resident Tapwater (Groundwater) Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIwater-nc-der	Resident Tapwater (Groundwater) Noncarcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIwater-nc-inh	Resident Tapwater (Groundwater) Noncarcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIwater-ca-ing	Recreation Tapwater (Groundwater) Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIwater-ca-der	Resident Tapwater (Groundwater) Carcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIwater-ca-inh	Resident Tapwater (Groundwater) Carcinogenic Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIres-water-ca-vc-ing	Resident Tapwater (Groundwater) Carcinogenic Vinyl Chloride Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIwater-ca-vc-der	Resident Tapwater (Groundwater) Carcinogenic Vinyl Chloride Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-water-ca-vc-inh	Resident Tapwater (Groundwater) Carcinogenic Vinyl Chloride Inhalation (mg/m3)	Contaminant-specific	Determined in this calculator
CDIwater-mu-ing	Resident Tapwater (Groundwater) Mutagenic Ingestion (mg/kg-day)	Mutagen-specific	Determined in this calculator
CDIwater-mu-der	Resident Tapwater (Groundwater) Mutagenic Dermal (mg/kg-day)	Mutagen-specific	Determined in this calculator
CDIwater-mu-inh	Resident Tapwater (Groundwater) Mutagenic Inhalation (mg/m3)	Mutagen-specific	Determined in this calculator
CDIrec-water-nc-ing	Recreation Surface Water Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-water-nc-der	Recreation Surface Water Noncarcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-water-ca-ing	Recreation Surface Water Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIrec-water-ca-der	Recreation Surface Water Carcinogenic Dermal (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-air-nc	Resident Air Noncarcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIres-air-ca	Resident Air Carcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIres-air-ca-vinyl chloride	Resident Air Carcinogenic Vinyl Chloride (mg/m3)	Vinyl Chloride-specific	Determined in this calculator
CDIres-air-mu	Resident Air Mutagenic (mg/m3)	Mutagen-specific	Determined in this calculator
CDIow-air-nc	Outdoor Worker Air Noncarcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIow-air-ca	Outdoor Workder Air Carcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIiw-air-nc	Indoor Worker Air Noncarcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIiw-air-ca	Indoor Workder Air Carcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIew-air-nc	Excavation/Construction Worker Air Noncarcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIew-air-ca	Excavation/Construction Workder Air Carcinogenic (mg/m3)	Contaminant-specific	Determined in this calculator
CDIres-fsh-nc-ing	Resident Fish Noncarcinogenic (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-fsh-ca-ing	Resident Fish Carcinogenic (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-fshw-nc-ing	Resident Surface Water Fish Noncarcinogenic (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIres-fshw-ca-ing	Resident Surface Water Fish Carcinogenic (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIag-prod-nc-ing	Agriculture Fruits and Vegetables Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIag-prod-ca-ing	Agriculture Fruits and Vegetables Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIw-ag-prod-nc-ing	Agriculture Fruits and Vegetables Noncarcinogenic Back-calculated Concentration in Water Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIw-ag-prod-ca-ing	Agriculture Fruits and Vegetables Carcinogenic Back-calculated Concentration in Water Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIs-ag-prod-nc-ing	Agriculture Fruits and Vegetables Noncarcinogenic Back-calculated Concentration in Soil Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIs-ag-prod-ca-ing	Agriculture Fruits and Vegetables Carcinogenic Back-calculated Concentration in Soil Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIag-milk-nc-ing	Agriculture Milk Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIag-milk-ca-ing	Agriculture Milk Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIw-ag-milk-nc-ing	Agriculture Milk Noncarcinogenic Back-calculated Concentration in Water Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIw-ag-milk-ca-ing	Agriculture Milk Carcinogenic Back-calculated Concentration in Water Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIs-ag-milk-nc-ing	Agriculture Milk Noncarcinogenic Back-calculated Concentration in Soil Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIs-ag-milk-ca-ing	Agriculture Milk Carcinogenic Back-calculated Concentration in Soil Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIag-beef-nc-ing	Agriculture Beef Noncarcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIag-beef-ca-ing	Agriculture Beef Carcinogenic Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIw-ag-beef-nc-ing	Agriculture Beef Noncarcinogenic Back-calculated Concentration in Water Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIw-ag-beef-ca-ing	Agriculture Beef Carcinogenic Back-calculated Concentration in Water Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIs-ag-beef-nc-ing	Agriculture Beef Noncarcinogenic Back-calculated Concentration in Soil Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
CDIs-ag-beef-ca-ing	Agriculture Beef Carcinogenic Back-calculated Concentration in Soil Ingestion (mg/kg-day)	Contaminant-specific	Determined in this calculator
Toxicity Values
RfDo	Chronic Oral Reference Dose (mg/kg-day)	Contaminant-specific	EPA Superfund hierarchy
RfC	Chronic Inhalation Reference Concentration (mg/m3)	Contaminant-specific	EPA Superfund hierarchy
CSFo	Chronic oral Slope Factor (mg/kg-day)-1	Contaminant-specific	EPA Superfund hierarchy
IUR	Chronic Inhalation Unit Risk (ug/m3)-1	Contaminant-specific	EPA Superfund hierarchy
Miscellaneous Variables
Csoil	concentration of contaminant in soil (mg/kg)	User-input
Cg-water	concentration of contaminant in groundwater (mg/L)	User-input
Cs-water	concentration of contaminant in surface water (mg/L)	User-input
Cair	concentration of contaminant in air (mg/m3)	User-input
Cfish	concentration of contaminant in fish (mg/kg)	User-input
Cproduce	concentration of contaminant in produce (mg/kg)	User-input
Cmilk	concentration of contaminant in milk (mg/kg)	User-input
Cbeef	concentration of contaminant in beef (mg/kg)	User-input
TR	target risk (unitless)	1 × 10-6	Determined in this calculator
THQ	target hazard quotient (unitless)	1	Determined in this calculator
Ingestion, Inhalation and Dermal Contact Exposure Parameters
K	Andelman Volatilization Factor (L/m3)	0.5	U.S. EPA 1991b (pg. 20)
Kp	permeability constant (cm/hr)	Contaminant-specific
BWa	Body Weight - adult (kg)	70	U.S. EPA 1991a (pg. 15)
BWc	Body Weight - child (kg)	15	U.S. EPA 1991a (pg. 15)
BWow	Body Weight - outdoor worker (kg)	70	U.S. EPA 1991a (pg. 15)
BWiw	Body Weight - indoor worker (kg)	70	U.S. EPA 1991a (pg. 15)
BWew	Body Weight - excavation/construction worker (kg)	70	U.S. EPA 1991a (pg. 15)
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-year/kg-day)	114	Calculated using the age-adjusted intake factors equation
IFSMadj	Mutagenic Resident Soil Ingestion Rate - Age-adjusted (mg-year/kg-day)	489.5	Calculated using the age-adjusted intake factors equation
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-year/kg-day)	1.086	Calculated using the age-adjusted intake factors equation
IFWMadj	Mutagenic Drinking Water Ingestion Rate - Age-adjusted (L-year/kg-day)	3.39	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)	14.8×103	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPfr-a	Produce Ingestion Rate - Fruit - Adult (mg/day)	56.2×103	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPfr-adj	Produce Ingestion Rate - Fruit - Age-adjusted (mg-year/kg-day)	25.2×103	Calculated using the aged adjusted intake factors equation
IRPvg-c	Produce Ingestion Rate - Vegetables - Child (mg/day)	10.4×103	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPvg-a	Produce Ingestion Rate - Vegetables - Adult (mg/day)	28.5×103	U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRPvg-adj	Produce Ingestion Rate - Vegetables - Age-adjusted (mg-year/kg-day)	13.9×103	Calculated using the aged adjusted intake factors equation
IRMc	Milk Ingestion Rate - Child (mg/day)	265×103	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRMa	Milk Ingestion Rate - Adult (mg/day)	615×103	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRMadj	Milk Ingestion Rate - Age-adjusted (mg-year/kg-day)	317×103	Calculated using the aged adjusted intake factors equation
IRBc	Beef Ingestion Rate - Child (mg/day)	12.9×103	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRBa	Beef Ingestion Rate - Adult (mg/day)	138×103	U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRBadj	Beef Ingestion Rate - Age-adjusted (mg-year/kg-day)	52.5×103	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.
BCF	Fish Bioconcentration Factor (L/kg)	Contaminant-specific
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
CFb	Fraction of Beef Consumed that is Contaminated	1	U.S. EPA 1998
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)
SAc	Resident soil surface area - child (cm2)	2800	U.S. EPA 2002 (Exhibit 1-2)
SAa	Resident soil surface area - adult (cm2)	5700	U.S. EPA 2002 (Exhibit 1-2)
SArec	Recreation surface water surface area (cm2)	18000	U.S. EPA 2004
AFc	Resident soil adherence factor-child (mg/cm2)	0.2	U.S. EPA 2002 (Exhibit 1-2)
AFa	Resident soil adherence factor-adult (mg/cm2)	0.07	U.S. EPA 2002 (Exhibit 1-2)
DFSadj	Resident soil dermal contact factor- age-adjusted (mg-year/kg-day)	361	Calculated using the age-adjusted intake factors equation
DFSMadj	Mutagenic Resident soil dermal contact factor- age-adjusted (mg-year/kg-day)	1445	Calculated using the age-adjusted intake factors equation
SAow	Outdoor Worker soil surface area - adult (cm2)	3300	U.S. EPA 2002 (Exhibit 1-2)
SAow	Excavation/Construction Worker soil surface area - adult (cm2)	3300	U.S. EPA 2002 (Exhibit 1-2)
AFow	Worker soil adherence factor-child (mg/cm2)	0.2	U.S. EPA 2002 (Exhibit 1-2)
AFew	Excavation/Construction Worker soil adherence factor-child (mg/cm2)	0.3	U.S. EPA 2002 (Exhibit 1-2)
ABSd	Fraction of contaminant absorbed dermally from soil (unitless)	Contaminant-specific	U.S. EPA 2004 (Exhibit 3-4)
GIABS	Fraction of contaminant absorbed in gastrointestinal tract (unitless) Note: if the GIABS is >50% then it is set to 100% for the calculation of dermal toxicity values.	Contaminant-specific	U.S. EPA 2004 (Exhibit 4-1)
Exposure Frequency, Exposure Duration, Exposure Time and Averaging Time Variables
ATr	Averaging time - resident (days/year)	365	U.S. EPA 1989 (pg. 6-23)
ATrec	Averaging time - recreation (days/year)	365	U.S. EPA 1989 (pg. 6-23)
ATow	Averaging time - outdoor worker (days/year)	365	U.S. EPA 1989 (pg. 6-23)
ATiw	Averaging time - indoor worker (days/year)	365	U.S. EPA 1989 (pg. 6-23)
ATew	Averaging time - excavation/construction worker (days/year)	365	U.S. EPA 1989 (pg. 6-23)
ATag	Averaging time - Agriculture (days/year)	365	U.S. EPA 1989 (pg. 6-23)
LT	Lifetime (years)	70	U.S. EPA 1989 (pg. 6-22)
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)
EFow	Exposure Frequency - outdoor worker (days/yr)	225	U.S. EPA 1991a (pg. 15)
EFiw	Exposure Frequency - indoor worker (days/yr)	250	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
EFag	Exposure Frequency - agricultural (days/yr)	350	U.S. EPA 1991a (pg. 15)
EDr	Exposure Duration - resident (yr)	30	U.S. EPA 1991a (pg. 15)
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)
ETres	Exposure Time - resident (hr/day)	24
ETrec	Exposure Time - recreation (hr/day)	1
ETow	Exposure Time - outdoor worker (hr/day)	8
ETiw	Exposure Time - indoor worker (hr/day)	8
ETew	Exposure Time - excavation/construction worker (hr/day)	8
ETc	Exposure time - child (hr/event)	1	U.S. EPA 2004
ETa	Exposure time - adult (hr/event)	0.58	U.S. EPA 2004
EV	Events (events/day)	1	U.S. EPA 2004
EVc	Events per day - child	1	U.S. EPA 2004
EVa	Events per day - adult	1	U.S. EPA 2004
Particulate Emission Factor Variables
PEFw	Particulate Emission Factor - Minneapolis (m3/kg)	1.36 x 109(region-specific)	Determined in this calculator
Q/Cwp	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)	Determined in this calculator
V	Fraction of Vegetative Cover (unitless)	0.5	U.S. EPA 1996a (pg. 23)
Um	Mean Annual Wind Speed (m/s)	4.69	U.S. EPA 1996a (pg. 23)
Ut	Equivalent Threshold Value of Wind Speed at 7m (m/s)	11.32	U.S. EPA 1996a (pg. 23)
F(x)	Function Dependent on Um /Ut(unitless)	0.194	U.S. EPA 1996a (pg. 23)
A	Dispersion constant unitless	PEF and region-specific	U.S. EPA 2002 (pg. D-6 to D-8)
As	Areal extent of the site or contamination (acres)	0.5 (range 0.5 to 500 )	U.S. EPA 2002 (pg. D-2)
B	Dispersion constant unitless	PEF and region-specific	U.S. EPA 2002 (pg. D-6 to D-8)
C	Dispersion constant unitless	PEF and region-specific	U.S. EPA 2002 (pg. D-6 to D-8)
Volatilization Factor Variables
VFs	Volatilization Factor - Minneapolis (m3/kg)	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
Q/Cwv	Inverse of the Mean Concentration at the Center of a 0.5-Acre-Square Source (g/m2-s per kg/m3)	68.81	U.S. EPA. 1996b (pg. 24)
DA	Apparent Diffusivity (cm2/s)	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
T	Exposure interval (s)	9.5 × 108	U.S. EPA. 1996b (pg. 24)
ρb	Dry soil bulk density (g/cm3)	1.5	U.S. EPA. 1996b (pg. 24)
θa	Air-filled soil porosity (Lair/Lsoil)	0.28	U.S. EPA. 1996b (pg. 24)
n	Total soil porosity ( Lpore/Lsoil)	0.43	U.S. EPA. 1996b (pg. 24)
θw	Water-filled soil porosity (Lwater/Lsoil)	0.15	U.S. EPA. 1996b (pg. 24)
ρs	Soil particle density (g/cm3)	2.65	U.S. EPA. 1996b (pg. 24)
Di	Diffusivity in air (cm2/s)	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
H'	Dimensionless Henry's Law Constant	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
Dw	Diffusivity in water (cm2/s)	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
Kd	Soil-water partition coefficient (Koc×foc)	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
Koc	Soil organic carbon-water partition coefficient	Contaminant-specific	U.S. EPA. 1996b (pg. 24)
foc	Organic carbon content of soil (g/g)	0.006	U.S. EPA. 1996b (pg. 24)