Jump to main content.

PRG Home PRG Search What's New Frequently Asked Questions User's Guide Equations Download Area

Preliminary Remediation Goals for Radionuclides

 Topics for Key Radiation Guidances and Reports

User's Guide

Disclaimer

This guidance document sets forth EPA's recommended approaches based upon currently available information with respect to risk assessment for response actions at CERCLA sites. This document does not establish binding rules. Alternative approaches for risk assessment may be found to be more appropriate at specific sites (e.g., where site circumstances do not match the underlying assumptions, conditions and models of the guidance). The decision whether to use an alternative approach and a description of any such approach should be documented. Accordingly, when comments are received at individual sites questioning the use of the approaches recommended in this guidance, the comments should be considered and an explanation provided for the selected approach.

The policies set out in the Radionuclide PRG User Guide provide guidance to EPA staff. It also provides guidance to the public and regulated community on how EPA intends the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) be implemented. EPA may change this guidance in the future, as appropriate.

It should also be noted that calculating a PRG addresses neither human noncancer toxicity, nor potential ecological risk. Of the radionuclides generally found, at CERCLA sites, only uranium has potentially significant noncancer toxicity. When assessing sites with uranium as a contaminant, it may also be necessary to consider the noncancer toxicity of uranium, using other tools, such as EPA's Screening Levels for Chemical Contaminants electronic calculator at http://epa-prgs.ornl.gov/chemicals/index.shtml. Similarly, some sites with radiological contaminants 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/oswer/riskassessment/pdf/ecorisk.pdf contains an eight step process for using benchmarks for ecological effects in the remedy selection process.

This web calculator may be used to develop generic PRGs for radionuclides for several different exposure scenarios. The calculator is flexible and may be used to derive site-specifc PRGs as more site characterization is obtained (EPA 2000a). Models reviewed by EPA in the Soil Screening Guidance - Radionuclide Technical Background Document at http://www.epa.gov/ada/download/reports/600R02082/600R02082-full.pdf in Section 3-2. This report provides a detailed technical analysis of five unsaturated zone fate and transport models for radionuclides. This report supports the information provided in Part 3 - Unsaturated Zone Models for Radionuclide Fate and Transport [PDF 383KB, 25 pages] of the Soil Guidance for Radionuclides: Technical Background Document on determining the general applicability of the models to subsurface conditions, and an assessment of each model's potential applicability to the soil screening process.

1. Introduction

A purpose of this guidance is to provide a PRG calculation tool to assist risk assessors, remedial project managers, and others involved with risk assessment and decision-making at CERCLA sites 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. Chemical-specific PRGs are from two general sources. These are: (1) concentrations based on potential Applicable or Relevant and Appropriate Requirements (ARARs) and (2) risk-based concentrations. ARARs include concentration limits set by other environmental regulations such as Safe Drinking Water Act maximum contaminant levels (MCLs). The second source for PRGs, and the focus of this database tool, is risk-based calculations that set concentration limits using carcinogenic toxicity values under specific exposure conditions.

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.

PRGs are presented for residential soil, outdoor worker soil, indoor worker soil, tap water, and fish ingestion. The risk-based PRGs for radionuclides are based on the carcinogenicity of the contaminants. Cancer slope factors used are from HEAST.

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 Soil Screening Guidance webpage.

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 (soil 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.

In addition to this guidance, for relevant training, see the internet-based course "Radiation Risk Assessment: Updates and Tools." http://www.epa.gov/superfund/health/contaminants/radiation/radrisk.htm#train

2. Understanding the PRG Website

2.1 General Considerations

PRGs are isotope concentrations that correspond to certain levels of risk in 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 most common land uses and exposure assumptions are included in the equations on this website: Residential Soil, Outdoor Worker Soil, Indoor Worker Soil, Agricultural Soil, Tapwater, Soil to Groundwater and Ingestion of Fish.

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. External exposure slope factors can also be used that have units of risk/yr per pCi/cm2 soil. When combined with site-specific media concentration data and appropriate exposure assumptions, slope factors can be used to estimate lifetime cancer risks to members of the general population due to radionuclide exposures.

2.2.1 When To Use "+D" PRGs

Several of the isotopes are listed with a “+D” designation. This designation indicates that the SF includes the contribution from ingrowth of daughter isotopes out to 100 years. The intention of this designation 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.) Before applying PRGs to a site, it should be determined if the isotopes present are in secular equilibrium. If the isotopes are found to be in secular equilibrium, the +D PRGs should be used for the parent isotope and the daughters included in the +D can be ignored. If the isotopes are not in secular equilibrium, PRGs should be applied for each daughter isotope. However, in the absence of empirical data, the "+D" values for radionuclides should be used unless there are compelling reasons not to.

For example, if analytical data from a site reveal that Th-228, Ra-224, Rn-220 are detected at a site and that they are in secular equilibrium, the PRG for Th-228+D should be applied and the Ra-224 and Rn-220 can be ignored.

Another example could concern a decay chain in secular equilibrium like Th-232. Even though the decay chain for Th-232 is very long, there is no Th-232+D slope factor. In this case the PRGs for Th-232, Ra-228+D, and Th-228+D should be used. If no part of the decay chain is in secular equilibrium, the user should use each of the PRGs for isotopes in the decay chain that have slope factors (e.g., Th-232, Ra-228, Ac-228, Th-228, Ra-224, Rn-220, Po-216, Pb-212, Bi-212, Po-212, and Tl-208). If part of the decay chain is in secular equilibrium, then the user may use that particular +D slope factor that covers that part of the decay chain, while using the slope factors for the other radionuclides.

2.2.2 Associated Decay Chains for "+D" PRGs

Selected radionuclides and radioactive decay chain products are designated with the suffix "+D" to indicate that cancer risk estimates for these radionuclides include the contributions from their short-lived decay products, assuming equal activity concentrations (i.e., secular equilibrium) with the principal or parent nuclide in the environment. For all radionuclides without the "+D" suffix, only intake or external exposure to the single radionuclide is considered. Most radionuclides with a +D designation include the entire decay chain to the stable terminal nuclide in the slope factors. HEAST provides a table of +D radionuclides that decay for longer than 100 years. This table provides the associated decay chain included and the terminal radionuclide used in the slope factors. This table is reproduced below.

Principal Radionuclide (half-life in years)  
Associated decay chain
Terminal Radionuclide 
Half-life (years)
Am-242m+D (152)
Am-242, Cm-242, Np-238
Pu-238
87.7
Am-243+D (7.4E+03)
Np-239
Pu-239
2.40E+04
Np-237+D (2.1E+06)
Pa-233
U-233
  
1.6E+05
Pu-244+D (8.3E+07)
U-240, Np-240m 
Pu-240
6.50E+03
Ra-226+D (1.6E+03) 
Rn-222, Po-218, Pb-214, At-218, Bi-214, Po-214, Tl-210 
Pb-210
  
22
Ra-228+D (6)
Ac-228
Th-228
  
2
U-235+D (7.0E+08)
Th-231
Pa-231
  
3.3E+04
U-238+D (4.5E+09)
Th-234, Pa-234m, Pa-234
U-234
  
2.4E+05

Ingestion and inhalation slope factors are missing for some of the +D isotopes. These have not been derived yet. Use caution when selecting a PRG to make sure that as many routes of exposure are accounted for.

2.3 PRG in Context of Superfund Modeling Framework

This PRG calculator focuses on the application of a 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 viewing either the tables in the Download Area section of this calculator or by running the PRG Search section of this calculator with the "Get Default PRGs" option. Part 3 of the Soil Screening Guidance for Radionuclides: Technical Background Document provides more information about more detailed approaches that are part of the same framework.

Generic 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.

The framework presented in Part 3 of the Soil Screening Guidance for Radionuclides: Technical Background Document includes more detailed modeling approaches that take into account more complex site conditions than the generic or simple site-specific methodology used in this calculator. More detailed approaches may be appropriate when site conditions (e.g., very deep water table, very thick uncontaminated unsaturated zone, soils underlain by karst or fractured rock aquifers) are substantially different than those assumed in the generic or simple-site methodology presented in this calculator. Further information on using more detailed approaches may be found in "Simulating Radionuclide Fate and Transport in the Unsaturated Zone: Evaluation and Sensitivity Analyses of Select Computer Models". This report provides a detailed technical analysis of five unsaturated zone fate and transport models for radionuclides.

3. Using the PRG Table

The PRG "Download Area" table provides generic concentrations in the absence of site-specific exposure assessments. Screening concentrations can be used for:

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.

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

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

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:

4. Technical Support Documentation

The PRGs consider human exposure to contaminated air, 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.

For a graphical representation and brief description of the routes of exposure for each exposure scenario, click on the name of the exposure scenarios below:

Residential Soil
Outdoor Worker Soil
Indoor Worker Soil
Agricultural Soil
Tapwater
Ingestion of Fish
Soil to Groundwater

Users should note that if a route of exposure (e.g., ingesting fish from the pond in the agricultural 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 (e.g., replacing default fish ingestion rates in agricultural soil scenario of 45.8 and 6.4 kg/yr with 0.0).

4.1 Residential Soil

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

A number of studies have shown that inadvertent ingestion of soil is common among children 6 years old and younger (Calabrese et al. 1989, Davis et al. 1990, Van Wijnen et al. 1990). Therefore, the dose method uses an age-adjusted soil ingestion factor that takes into account the difference in daily soil ingestion rates, body weights, and exposure duration for children from 1 to 6 years old and others from 7 to 30 years old. The equation is presented below. This health-protective approach is chosen to take into account the higher daily rates of soil ingestion in children as well as the longer duration of exposure that is anticipated for a long-term resident. For more on this method, see RAGS Part B.

Age adjusted intake factors are also used for inhalation of particulates emitted from soil, and consumption of fruits and vegetables. These equations are also presented in the above equations.

4.1.1 Residential Soil Alternate External Exposure Analysis

4.2 Residential Air

Two ambient air exposure equations are presented below. The first equation includes a half-life decay function and the second equation does not. In situations where the contaminant in the air is not being replenished (e.g., contaminated settled dust from a previous release that is being resuspended), the first equation should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil), the second equation should be used.

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

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

4.3 Outdor Worker Soil

The outdoor worker soil land use equation, presented here, contains the following exposure routes:

4.3.1 Outdoor Worker Soil Alternate External Exposure Analysis

4.4 Outdoor Worker Air

Two sets of ambient air exposure equations are presented below. The first set of equations includes a half-life decay function and the second set of equations does not. In situations where the contaminant in the air is not being replenished (e.g., contaminated settled dust from a previous release that is being resuspended), the first equation should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil), the second equation should be used.

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

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

4.5 Indoor Worker Soil

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

4.5.1 Indoor Worker Soil Alternate External Exposure Analysis

4.6 Indoor Worker Air

Two sets of ambient air exposure equations are presented below. The first set of equations include a half-life decay function and the second set of equations does not. In situations where the contaminant in the air is not being replenished (e.g., contaminated settled dust from a previous release that is being resuspended), the first equation should be used. In situations where the contaminant in the air has a continual source (e.g., indoor radon from radium in the soil), the second equation should be used.

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

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

4.7 Farmer

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

The following equations expand the individual exposure routes.

The age-adjusted intake equations for the agricultural land use are presented below. They are: soil ingestion, inhalation, vegetables, fruit, swine, poultry, egg, milk, beef, and fish.

4.8 Tapwater

4.8.1 Resident

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

4.9 Ingestion of Fish

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

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

4.10 Soil to Groundwater

The method for calculating SSLs for the migration to groundwater pathway was developed to identify radionuclide concentrations in soil that have the potential to contaminate groundwater above screening levels (i.e., MCLs or risk-based concentrations (RBCs). Migration of radionuclides from soil to groundwater can be envisioned as a two-stage process: (1) release of contaminant in soil leachate and (2) transport of the contaminant through the underlying soil and aquifer to a receptor well. The SSL method considers both of these fate and transport mechanisms.

SSLs are backcalculated from acceptable groundwater concentrations. First, the acceptable groundwater concentration is multiplied by a dilution factor to obtain a target leachate concentration. For example, if the dilution factor is 10 and the acceptable groundwater concentration is 10 pCi/L, the target soil leachate concentration would be 100 pCi/L. The partition equation is then used to calculate the total soil concentration (i.e., SSL) corresponding to this soil leachate concentration.

The user has the option to choose from two calculation methods. The first method employs the default partitioning equation for migration to groundwater. The dilution factor defaults to 20 for a 0.5-acre source. If the user has all of the parameters needed to calculate a dilution factor, you may use the Method 2 (mass-limit equation for migration to groundwater).

Method 1. Partitioning Equation for Migration to Groundwater

Method 2. Mass-Limit Equation for Migration to Groundwater

Then calculate the dilution factor using this equation.

where:

4.11 Supporting Equations and Parameter Discussion

There are four 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 explanation of the groundwater transport portion of the equations involving the soil to water partition coefficient (Kd). The third is the use of the radionuclide decay constant (). The fourth 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 Groundwater Transport

For the agricultural soil land use, the fish, milk, beef, and swine exposure routes contain input parameters that allow for partitioning of contaminants in soil to groundwater. The transport equation is presented below. By doing this, the PRG is solely based on soil activity. Definitions of the input variables are in Table 1. The approach for soil partitioning (e.g., equation and exposure parameters) are based on the "rural residential" exposure scenario that was part of the U.S. EPA, Office of Air and Radiation, Technical Support Document For The Development of Radionuclide Cleanup Levels For Soil, EPA 402-R-96-011 A, September 1994. The formula for the soil partitioning can be found in Appendix C.

4.11.3 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-214and Po-214) in air. ) In most cases, site-specific analytical data should be used to establish the actual degree of equilibrium between each parent radionuclide and its decay products in each media sampled. However, in the absence of empirical data, the "+D" values for radionuclides should be used unless there are compelling reasons not to. 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.

4.11.4 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 PRGs, 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 recommended PRGs. For the 2-D exposure models addressing finite areas, the ACF is made variable by isotope and area for site-specific analysis. This calculator allows the user to select from 8 different soil area sizes. If no size is selected for the finite analysis, the ACF from the most protective area size is selected. For further information on the derivation of the isotope-specific/area-specific ACF values for 2-D areas see Contaminated Slabs. For a description of other EPA default ACF values, follow the link here.

Table 1. Recommended Standard Default Factors

Symbol Definition (units) Default Reference
Slope Factors
SFs Ingestion Slope Factor - soil (risk/pCi) -- HEAST
SFf Ingestion Slope Factor - food (risk/pCi) -- HEAST
SFw Ingestion Slope Factor - water (risk/pCi) -- HEAST
SFi Slope Factor - inhalation (risk/pCi) -- HEAST
SFext-sv Slope Factor - external exposure (risk/yr per pCi/g) -- HEAST
SFext-1cm Slope Factor - external exposure (risk/yr per pCi/g) -- HEAST
SFext-5cm Slope Factor - external exposure (risk/yr per pCi/g) -- HEAST
SFext-15cm Slope Factor - external exposure (risk/yr per pCi/g) -- HEAST
SFext-gp Slope Factor - external exposure (risk/yr per pCi/cm2) -- HEAST
Dose and Decay Constant Variables
TR Target Risk 1 × 10-06
tw Time - worker (years) 25 U.S. EPA 1991a (pg. 15)
tr Time - resident (years) 30 U.S. EPA 1991a (pg. 15)
tag Time - agriculture (years) 40 U.S. EPA 1994a EPA 1998 (Table C-1-7)
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) Isotope-specific Eckerman 2007
GSF Gamma Shielding Factor (unitless) 0.4 U.S. EPA 2000a. (pg. 2-22). U.S. EPA 2000b. (pg. 2-18)
CPFr Contaminated Plant Fraction - resident (unitless) 0.25 U.S. EPA 1990. U.S. EPA. 1998. (pg. 6-6)
CPFag Contaminated Plant Fraction - agricultural (unitless) 1 U.S. EPA 1994c. U.S. EPA. 1998. (pg. 6-6)
K Andelman Volatilization Factor (L/m3) 0.5 U.S. EPA 1991b (pg. 20)
Tissue Transfer Factors and Animal Ingestion Rates of Fodder, Water, and Soil
TFp Soil to Plant Transfer Factor (day/kg) -- ANL. 1993. NCRP 1996. U.S. EPA 2000a. (pg. C-8)
TFf Fish Transfer Factor (day/kg) -- ANL. 1993. NCRP 1996.
TFb Beef Transfer Factor (day/kg) -- ANL. 1993. NCRP 1996.
TFm Milk Transfer Factor (day/kg) -- ANL. 1993. NCRP 1996.
TFsw Swine Transfer Factor (day/kg) -- IAEA 1994. (Table XVIII)
TFpo Poultry Transfer Factor (day/kg) -- IAEA 1994. (Table XIX)
TFe Egg Transfer Factor (day/kg) -- IAEA 1994. (Table XIX)
FIb Beef Fodder Intake Rate (kg/day) 11.77 U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
FIsb Beef Soil Intake Rate (kg/day) 0.39 U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
FIwb Beef Water Intake Rate (kg/day) 53 U.S. EPA 1999a (pg 10-23).
FIm Dairy Fodder Intake Rate (kg/day) 16.9 U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
FIsm Dairy Soil Intake Rate (kg/day) 0.41 U.S. EPA 1999a (pg 10-23). U.S. EPA 1997b.
FIwm Dairy Water Intake Rate (kg/day) 92 U.S. EPA 1999a (pg 10-23).
FIsw Swine Fodder Intake Rate (kg/day) 4.7 U.S. EPA 1998 (pg. 5-56)
FIssw Swine Soil Intake Rate (kg/day) 0.37 U.S. EPA 1998 (pg. 5-57)
FIwsw Swine Water Intake Rate (kg/day) 11.4 NEC (pg. 19)
FIpo Poultry Fodder Intake Rate (kg/day) 0.2 U.S. EPA 1998 (pg. 5-60)
FIpos Poultry Soil Intake Rate (kg/day) 0.022 U.S. EPA 1998 (pg. 5-61)
Inhalation, Ingestion, and Consumption Rates
IRir Inhalation Rate -resident (m3/day)   Calculated using the aged adjusted intake factors equation
IRiag Inhalation Rate -agriculture (m3/day)   Calculated using the aged adjusted intake factors equation
IRtap Inhalation Rate -tapwater (m3/day) 20 U.S. EPA 1991a (pg. 15)
IRAa Inhalation Rate - adult resident and agriculture (m3/day) 20 U.S. EPA 1991a (pg. 15)
IRAc Inhalation Rate - child resident and agriculture (m3/day) 10 U.S. EPA 1997a (pg. 5-11)
IRiw Inhalation Rate - indoor worker (m3/day; based on a rate of 2.5m3/hr for 24hr) 60 U.S. EPA 1997a (pg. 5-11)
IRow Inhalation Rate - outdoor worker (m3/day; based on a rate of 2.5m3/hr for 24hr) 60 U.S. EPA 1997a (pg. 5-11)
IRw Drinking Water Ingestion Rate (L/day) 2 U.S. EPA 1989 (Exhibit 6-11)
IRsr Soil Ingestion Rate - resident (mg/day)   Calculated using the aged adjusted intake factors equation
IRsag Soil Ingestion Rate - agriculture (mg/day)   Calculated using the aged adjusted intake factors equation
IRa Soil Ingestion Rate - adult resident and agriculture (mg/day) 100 U.S. EPA 1991a (pg. 15)
IRc Soil Ingestion Rate - child resident and agriculture (mg/day) 200 U.S. EPA 1991a (pg. 15)
IRsow Soil Ingestion Rate - outdoor worker (mg/day) 100 U.S. EPA 2001 (pg. 4-3)
IRsiw Soil Ingestion Rate - indoor worker (mg/day) 50 U.S. EPA 1991a (pg. 15)
CRvr Vegetable Ingestion Rate - resident (kg/yr)   Calculated using the aged adjusted intake factors equation
CRvag Vegetable Ingestion Rate - agriculture (kg/yr)   Calculated using the aged adjusted intake factors equation
CRva Vegetable Ingestion Rate - adult resident and agriculture (kg/yr) 10.4 U.S. EPA 1997a (Table 13-65). U.S. EPA 1998 (Table C-1-2)
CRvc Vegetable Ingestion Rate - child resident and agriculture (kg/yr) 3.8 U.S. EPA 1997a (Table 13-65). U.S. EPA 1998 (Table C-1-2)
CRfr Fruit Ingestion Rate - resident (kg/yr)   Calculated using the aged adjusted intake factors equation
CRfag Fruit Ingestion Rate - agriculture (kg/yr)   Calculated using the aged adjusted intake factors equation
CRfa Fruit Ingestion Rate - adult resident and agriculture (kg/yr) 20.5 U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
CRfc Fruit Ingestion Rate - child resident and agriculture (kg/yr) 5.4 U.S. EPA 1997a (Table 13-61). U.S. EPA 1998 (Table C-1-2)
IRff Fish Ingestion Rate - ingestion of fish land use (g/day) 54 U.S. EPA 1991a (pg. 15)
IRfag Fish Ingestion Rate - agriculture land use (kg/yr)   Calculated using the aged adjusted intake factors equation
IRfa Fish Ingestion Rate - agriculture land use adult (kg/yr) 45.8 U.S. EPA 1997a (Table 13-23)
IRfc Fish Ingestion Rate - agriculture land use child (kg/yr) 6.4 U.S. EPA 1997a (Table 13-23)
IRm Milk Ingestion Rate (kg/yr)   Calculated using the aged adjusted intake factors equation
IRma Milk Ingestion Rate - adult (kg/yr) 224.4 U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRmc Milk Ingestion Rate - child (kg/yr) 96.9 U.S. EPA 1997a (Table 13-28). U.S. EPA 1998 (Table C-1-3)
IRb Beef Ingestion Rate (kg/yr)   Calculated using the aged adjusted intake factors equation
IRba Beef Ingestion Rate - adult (kg/yr) 50.2 U.S. EPA 1997a (Table 13-36). U.S. EPA 1998 (Table C-1-3)
IRbc Beef Ingestion Rate - child (kg/yr) 4.7 U.S. EPA 1997a (Table 13-36). U.S. EPA 1998 (Table C-1-3)
IRsw Swine Ingestion Rate (kg/yr)   Calculated using the aged adjusted intake factors equation
IRswa Swine Ingestion Rate - adult (kg/yr) 27.7 U.S. EPA 1997a (Table 13-54). U.S. EPA 1998 (Table C-1-3)
IRswc Swine Ingestion Rate - child (kg/yr) 4.5 U.S. EPA 1997a (Table 13-54). U.S. EPA 1998 (Table C-1-3)
IRe Egg Ingestion Rate (kg/yr)   Calculated using the aged adjusted intake factors equation
IRea Egg Ingestion Rate - adult (kg/yr) 14.9 U.S. EPA 1997a (Table 13-43). U.S. EPA 1998 (Table C-1-3)
IRec Egg Ingestion Rate - child (kg/yr) 2.3 U.S. EPA 1997a (Table 13-43). U.S. EPA 1998 (Table C-1-3)
IRpo Poultry Ingestion Rate (kg/yr)   Calculated using the aged adjusted intake factors equation
IRpoa Poultry Ingestion Rate - adult (kg/yr) 35.8 U.S. EPA 1997a (Table 13-55). U.S. EPA 1998 (Table C-1-3)
IRpoc Poultry Ingestion Rate - child (kg/yr) 5 U.S. EPA 1997a (Table 13-55). U.S. EPA 1998 (Table C-1-3)
Exposure Frequency, Exposure Duration, and Exposure Time Variables
EFr Exposure Frequency - residential (days/yr) 350 U.S. EPA 1991a (pg. 15)
EFt Exposure Frequency - tapwater (days/yr) 350 U.S. EPA 1991a (pg. 15)
EFag Exposure Frequency - agricultural (days/yr) 350 U.S. EPA 1991a (pg. 15)
EFf Exposure Frequency - fish (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)
EDr Exposure Duration - resident (yr) 30 U.S. EPA 1991a (pg. 15)
EDt Exposure Duration - tapwater (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)
EDar Exposure Duration - adult resident (yr) 24 U.S. EPA 1991a (pg. 15)
EDaag Exposure Duration - adult agricultural (yr) 34 U.S. EPA 1994a
EDcr Exposure Duration - child resident (yr) 6 U.S. EPA 1991a (pg. 15)
EDcag Exposure Duration - child agriculture (yr) 6 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)
ETiwi Indoor Worker Exposure Time - indoor (hr/hr) 0.33 Eight Hours per 24 hr Day
ETiwo Indoor Worker Exposure Time - outdoor (hr/hr) 0  
ETowi Outdoor Worker Exposure Time - indoor (hr/hr) 0  
ETowo Outdoor Worker Exposure Time - outdoor (hr/hr) 0.33 Eight Hours per 24 hr Day
ETri Resident Exposure Time - 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 Resident Exposure Time - 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)
ETagi Agricultural Exposure Time - 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)
ETago Agricultural Exposure Time - 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)
Groundwater Transport Variables
Kd Soil to water partition coefficient (L/kg) -- U.S. EPA 2000a. (pg. C-6). U.S. EPA 2000b. (pg. 5-2). U.S. EPA 1999b
DFw Dilution Factor for Drinking Water (unitless) 1 U.S. EPA 1994b. (pg. C-5, 6, 8, and 9)
Aw Surface Area of Watershed (m2) 100000 U.S. EPA 1994b. (pg. C-9)
S Fraction Water Content (L water/L pore space) 0.3 U.S. EPA 1994b. (pg. C-5, 6, 8, and 9)
σ Total Soil Porosity (L water/L pore space) 0.5 U.S. EPA 1994b. (pg. C-5, 6, 8, and 9)
ρ Soil Bulk Density (kg/L soil) 1.5 U.S. EPA 1994b. (pg. C-5, 6, 8, and 9)
Soil to Groundwater Variables
SSL Soil Screening Level in Soil (pCi/g) Calculated U.S. EPA 1996a (pg. 29-31)
Cw Target Soil Leachate Concentration (pCi/L) MCL or RBC ×DAF U.S. EPA 1996a (pg. 29-31)
I Infiltration Rate (meters/year) Site-specific U.S. EPA 1996a (pg. 29-31)
EDgw Exposure Duration (year) 70 U.S. EPA 1996a (pg. 29-31)
ρb Dry Soil Bulk Density (kg/L) 1.5 U.S. EPA 1996a (pg. 29-31)
ds Depth of Source (meter) Site-specific U.S. EPA 1996a (pg. 29-31)
DAF Dilution Factor (unitless) 20 (0.5 acre source) or Site-specific U.S. EPA 1996a (pg. 29-31)
K Aquifer Hydraulic Conductivity (meter/year) Site-specific U.S. EPA 1996a (pg. 29-31)
i Hydraulic Gradient (meter/meter) Site-specific U.S. EPA 1996a (pg. 29-31)
d Mixing Zone Depth (m) Site-specific U.S. EPA 1996a (pg. 29-31)
L Source Length Parallel to Groundwater Flow (m) Site-specific U.S. EPA 1996a (pg. 29-31)
da Aquifer Thickness (m) Site-specific U.S. EPA 1996a (pg. 29-31)
θ Water-filled Soil Porosity (Lwater/Lsoil) 0.3 U.S. EPA 1996a (pg. 29-31)
Kd Soil-water Partition Coefficient (L/Kg) Chemical-specific U.S. EPA 1996a (pg. 29-31)
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/Cw 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)
A Dispersion constant unitless PEF and region-specific U.S. EPA 2002 (App D)
As Areal extent of the site or contamination (acres) 0.5 (range 0.5 to 500 ) U.S. EPA 2002 (App D)
B Dispersion constant unitless PEF and region-specific U.S. EPA 2002 (App D)
C Dispersion constant unitless PEF and region-specific U.S. EPA 2002 (App D)
ANL 1993. Manual for Implementing Residual Radioactive Materials Guidelines Using RESRAD, Version 5.0. Argonne National Laboratory, Argonne, IL. ANL/EAD/LD-2

Eckerman. 2007. Ratios of Dose Rates for Contaminated Slabs . K.F. Eckerman. September 20, 2007.

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. (Also see U.S. EPA. 1994c for direct link to Table) http://www.epa.gov/ORD/exposure/exposure.pdf

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.htm View Appendix C here

U.S. EPA. 1994c. Revised Draft Guidance for Performing Screening Level Risk Analyses at Combustion Facilities Burning Hazardous Wastes. Attachment C, Draft Exposure Assessment Guidance for RCRA Hazardous Waste Combustion Facilities. Office of Emergency and Remedial Response. Office of Solid Waste. December 14. http://www.epa.gov/earth1r6/6pd/rcra_c/protocol/volume_3/appc1-8.pdf

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

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

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

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

U.S. EPA. 1998. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. Office of Solid Waste, Washington, DC. EPA530-D-98-001A 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. http://www.epa.gov/cgi-bin/claritgw?op-Display&document=clserv:OAR:0232;&rank=4&template=epa

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

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

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

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

back to top

This site is maintained and operated through an Interagency Agreement between the EPA Office of Superfund and Oak Ridge National Laboratory. For questions or comments please contact Stuart Walker at the Office of Superfund Remediation and Technology Innovation.

OSWER Home | Waste and Cleanup Risk Assessment Home | Customer Satisfaction Survey

Local Navigation

Jump to main content.