This page presents many questions asked by site users and the applicable responses. Please search this page for answers to your questions prior to contacting technical support staff. Researching the questions and answers posted here will greatly reduce the time it takes for you to solve many problems that arise from calculating BDCCs and using this BDCC site.

1. What are BDCCs?
2. What are BDCCs used for?
3. What are radionuclide dose conversion factors (DCF)?
4. How should dose conversion factors (DCF) be used?
5. What dose-based radiation standards may be applicable or relevant and appropriate requirements (ARAR)?
6. How do BDCCs differ from cleanup standards?
7. How often do you update the BDCC Table?
8. Can I get a copy of a previous BDCC table?
9. What ages and exposure routes are considered in each land use?
10. How can I select more than one isotope at a time in the BDCC Search page?
11. How are the BDCC results converted to a mass basis?
12. How are the residential exposure durations (EDs) determined for carcinogenic (age-adjusted) exposures?
13. How can I get the calculator results or the other web pages to print on one page?
14. Do the BDCCs take into account field survey or laboratory analytical approaches?
15. Are the BDCCs applicable to cleanup after a terrorist attack?
16. Do the BDCCs factor inhalation from Radon vapor intrusion?
17. What is the preferred citation for information taken from this website?
18. Where else can I go for toxicity studies (values) not on this site?
19. How do the ingestion and external BDCC values compare to the DCC values for dust?
20. How does the peak annual dose (mrem) relate to dose limit and the Peak BDCC?
21. Are the future times given for some of the Peak DCCs, that are thousands to billions of years, meaningful?
22. What is the purpose of the calculator opening a new tab after I hit each retrieve button?

1. What are BDCCs?

   The recommended BDCCs (Dose Compliance Concentrations for Radionuclides in Buildings) presented on this site are dose-based concentrations, derived from standardized equations combining exposure information assumptions with EPA dose conversion factors, that are used for Superfund/RCRA programs. They are designed by the Agency to achieve protective cleanup levels for humans (including sensitive groups) over a lifetime. Recommended BDCCs are not always applicable to a particular site, however, and do not address non-human health endpoints such as ecological impacts. The recommended BDCCs contained in the BDCC table are generic; that is, they are calculated without site-specific information. They may be re-calculated using site-specific data.

2. What are BDCCs used for?

   BDCCs often are used for site "screening" and as initial cleanup goals, if appropriate. The recommended BDCCs on this site are not de facto cleanup standards and should not be applied as such. The recommended BDCC's role in site "screening" is typically to help identify areas, contaminants, and conditions that do not require further federal attention at a particular site. Generally, at sites where contaminant concentrations fall below BDCCs, no further action or study is warranted under the Superfund program, so long as the exposure assumptions at a site match those taken into account by the BDCC calculations. Radionuclide concentrations above the BDCC would not automatically designate a site as "dirty" or trigger a response action. Exceeding a BDCC suggests that further evaluation of the potential dose that may be posed by site contaminants is appropriate. BDCCs may also be useful tools for identifying initial cleanup goals at a site. In this role, BDCCs can provide long-term targets to use during the analysis of different remedial alternatives. By developing BDCCs early in the decision-making process, design staff may be able to streamline the consideration of remedial alternatives.

3. What are radionuclide dose conversion factors (DCF)?

   Dose conversion factors (DCFs), or "dose coefficients", for a given radionuclide represent the dose equivalent per unit intake (i.e., ingestion or inhalation) or external exposure of that radionuclide. These DCFs are used to convert a radionuclide concentration in dust, air, or soil to a radiation dose. DCFs 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, which are included in this DCC electronic calculator. These DCFs 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 dose equivalent to the receptor.

4. How should dose conversion factors (DCF) be used?

   The primary use of DCFs is to compare doses from site-related exposures with radiation protection standards and dose limits that are determined to be ARARs. This is accomplished by multiplying the exposure estimates (i.e., the intake of each radionuclide of concern via inhalation and ingestion and the duration of exposure and concentration of each radionuclide of concern in environmental media for external exposure) by the appropriate DCF values for that exposure pathway and radionuclide. Unlike excess cancer risk, which represents cumulative lifetime exposure, dose estimates are typically expressed in terms of annual exposure (e.g., the effective dose equivalent resulting from exposure during a one-year period, mrem/year).

5. What dose-based radiation standards may be applicable or relevant and appropriate requirements (ARAR)?

   In some cases, cleanup levels may be derived based on compliance with ARARs. Attachment A, "Likely Federal Radiation Applicable or Relevant and Appropriate Requirements (ARARs)", of OSWER Directive 9200.4-18 (U.S. EPA 1997a) provides guidance to use federal standards that have often been selected as ARARs that may be either applicable or relevant and appropriate for particular site-specific conditions. NOTE: EPA has determined that NRC decommissioning requirements (e.g., 25 or 100 mrem/yr dose limits) under 10 CFR 20 Subpart E should generally not be used to establish cleanup levels under CERCLA, even when these regulations are ARARs.

6. How do BDCCs differ from cleanup standards?

   BDCCs are not designed to serve as de facto cleanup standards; however, they could be used to help establish final cleanup levels for a site after a proper evaluation takes place. In the Superfund remedial program, part of this evaluation typically is carried out as part of the nine criteria analysis for remedy selection, addressed in the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The site-specific cleanup level, which can be based in part on BDCCs, is documented in the Record of Decision.

7. How often do you update the BDCC Table?

   The tables are updated when new toxicity values become available, exposure parameter values change, or a model is updated that impacts the default calculator results. There is no set schedule for these updates. Please take note of the "What's New" page to identify when these updates are incorporated.

8. Can I get a copy of a previous BDCC table?

   We do not distribute outdated copies of the recommended BDCC table. Each new version of the table supersedes all previous versions. If you wish to maintain previous versions of the BDCCs for a long-term project, you can download the entire table and save multiple versions with a time-stamp.

9. What ages and exposure routes are considered in each land use?

   The following table lists the land uses, media, and receptor ages utilized in the BDCC calculator.

   Land use	Media	Exposure Routes
   		Oral	Externala	Inhalation
   Resident	Dust	Adult Child	Adult Child	All Ages
   	Air	NA	All Ages	Adult Child
   Indoor Worker	Dust	Adult	Adult	Adult
   	Air	NA	Adult	Adult

   NA = Not Applicable
   ^a. the external exposure routes include external exposure to ionizing radiation in dust and submersion in air.

10. How can I select more than one isotope at a time in the BDCC Search page?

    To select more than one isotope you can:

    1. Left click and hold the button down while dragging the mouse pointer up and down through the isotope list,
    2. Hold the control (Ctrl) key down while left clicking on the isotopes desired, or
    3. Click in the "Select All" box to the bottom right of the isotope list.

11. How are the BDCC results converted to a mass basis?

    Appendix B of the Soil Screening Guidance for Radionuclides Technical Background Document presents a formula for converting BDCCs in pCi/g to mg/kg and also a formula for converting pCi/L to mg/L. The equation is reproduced here with similar conversions for mg/m³ and mg/cm².

    
    

    The derivation of the 2.8 × 10^-12 and the 2.8 × 10^-15 conversions are presented below.

    
    

    Combination of the derivation of the conversions with the isotope-specific half-life and atomic weight is presented here.

    

    
    

12. How are the residential exposure durations (EDs) determined for carcinogenic (age-adjusted) exposures?

    Residential exposure duration (ED_res) is set at 26 years, according to an OSWER directive based on the 2011 version of the Exposure Factor's Handbook. When evaluating carcinogenic exposure, intakes are age-adjusted to account for exposure as a child and an adult within the 26 years. The OSWER directive sets child exposure at 6 years (ED_res-c). Therefore, ED_res - ED_res-c = 20 years of adult exposure (ED_res-a). For this tool, child intakes are used with ED_res-c and adult intakes are used for ED_res-a.

13. How can I get the calculator results or the other web pages to print on one page?

    Output links for PDF and Spreadsheet files can be found at the top of the calculator results page. The HTML results are not suited for formatting to print on a single page but are rather designed for ease of use on the screen.

14. Do the BDCCs take into account field survey or laboratory analytical approaches?

    No, the BDCCs are a dose-based tool only. Determining the extent of contamination is a separate process during the Remedial Investigation or Feasibility Study (RI/FS) and remedial design processes. It is important for remedial decision data to be of known and acceptable quality. The determination of what data are needed is a site-specific decision, and it is the responsibility of the Remedial Project Manager (RPM) to use the tools that are most appropriate for that situation.

15. Are the BDCCs applicable to cleanup after a terrorist attack?

    Responses to radiological and nuclear terrorist incidents is addressed in an August 1, 2008, guidance issued by the Department of Homeland Security (DHS) in the Federal Register (Vol. 73, No. 149, pp 45029 - 45049), Planning Guidance for Protection and Recovery Following Radiological Dispersal Device (RDD) and Improvised Nuclear Device (IND) Incident. The DHS guidance uses Operational Guidelines from the Department of Energy to guide the early and intermediate phases of response to an RDD and an IND. Under the guidance, the late-phase generally would utilize an optimization process to site-specifically decide on an approach for addressing the remaining residual contamination. Normally, the BDCC calculator would be used only if the optimal process for the late-phase was a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) approach. As at a CERCLA site, the user at an RDD or IND site can choose to modify the standard default BDCC exposure parameters to calculate site-specific DCCs. The characteristics of an RDD or IND site may warrant the use of site-specific assumptions that differ from the BDCC defaults. The site manager should weigh the cost of collecting the data necessary to develop site-specific DCCs with the potential for deriving a higher BDCC that provides an appropriate level of protection.

16. Do the BDCCs factor inhalation from Radon vapor intrusion?

    Air BDCCs represent dose compliance concentrations for radionuclides in buildings for indoor air. The residential and indoor worker air BDCC values can be used to determine building dose compliance concentrations that are detected in the indoor air from a variety of sources. There are no BDCCs specific to the vapor intrusion pathway (i.e, for subsurface sources that may contribute to indoor air contamination). EPA's recommended Radon Vapor Intrusion Screening Level tool can be found online here. For guidance on vapor intrusion assessment, see EPA's Vapor Intrusion Site. The OSWER Technical Guide For Assessing And Mitigating The Vapor Intrusion Pathway From Subsurface Vapor Sources To Indoor Air (OSWER Publication 9200.2-154; June 2015) can be found there among other resources and information.

17. What is the preferred citation for information taken from this website?

    United States Environmental Protection Agency. Dose Compliance Concentrations for Radionuclide Contaminants in Buildings at Superfund Sites. (insert date accessed and url).

18. Where else can I go for toxicity studies (values) not on this site?

    Many other websites host toxicity information from other countries and other government agencies similar to this EPA site. The Risk Assessment Information System (RAIS) at http://rais.ornl.gov/ presents toxicity values and toxicity study information. Websites of other governmental agencies are also useful. The user may call the U.S. EPA Superfund Health Risk Technical Support Center at (513) 569-7300 and ask for toxicity values. The user may also call the ATSDR Information Center toll-free at 1-888-422-8737 for toxicity values and profiles.

19. How do the BDCC ingestion and external values for settled dust compare to the DCC values for soil?

    Some users have questioned why the proportion of dose posed by dust ingestion for external exposure with BDDCs is much greater than the proportion of dose from soil ingestion for external exposure with DCCs. The BDCC ingestion values are based on the transfer of dust to a receptor's hand and subsequent transfer of the dust from the hand to the receptor's mouth. The BDCC ingestion values are reported in units of square centimeters (area) and collected by surface wipe samples. The DCC ingestion values are based on the incidental ingestion of soil throughout the time period, regardless of the intake method. The DCC ingestion values are reported in units of grams (mass) and collected by digging and weighing samples. While the units of the ingestion BDCCs are different than the units of the ingestion DCCs, there is a correlation. If the mass of dust in an area is known, a BDCC can be converted to a DCC. This conversion factor is known as the dust mass loading factor with units of mass/area.

    Consider the Ra-226 indoor worker default ingestion DCC of 9.88 pCi/g and the indoor worker default ingestion BDCC of 0.0028 pCi/cm² . Assume a dust mass loading factor of 0.2834 mg/cm² . The equation below shows the relationship.

    DCC 9.88 pCi/g x 1 g/1000 mg x 0.2834 mg/cm² = BDCC 0.0028 pCi/cm² .

    In the report, Dust: A Metric for Use in Residential and Building Exposure Assessment and Source Characterization, dust loading factors are given that range from 0.05 to 99 g/m² or 0.005 to 9.9 mg/cm² . The dust loading factor used in the above equation was derived to fit the conversion between a DCC and BDCC and is well within the range of the values presented in the referenced report.

    The BDCC external values are based on ground plane exposure, and the DCC external values are based on infinite soil volume exposure. Comparing ground plane to soil volume external route results is not valid for the following reasons:

    • The source thicknesses are different.
    • The DCC equation uses gamma shielding from the subfloor and the BDCC does not.
    • The DCC equation uses an area correction factor and the BDCC does not.
    • The DCC units are mass-based and the BDCC units are area-based.
    • The BDCC equation is based on soil and the BDCC equation isn't based on any source matrix.

20. How does the peak annual dose rate (mrem) relate to dose limit and the Peak BDCC?

    Peak annual dose rate (mrem) = Total dose for the one-year period in which the dose is greatest for a parent and all progeny, considering the scenario inputs, routes of exposure, and toxicity.

    Peak dose interval = the time period in years (exposure duration, ED) encompassing the peak dose rate with the maximum dose across all possible intervals with the exhaustion of decay.

    DL = dose limit for selected scenario.

    Peak Dose DCC = the concentration at which the parent and progeny achieve the DL within the peak dose interval.

    Consider the plot below for Ra-226 default dust ingestion peak BDCC for a indoor worker. The peak dose rate is the maximum sum of the dose contribution from all chain members for a year. To calculate the dose contribution of the chain members, determine the activity by decaying the parent and ingrowing progeny for all time using a Bateman equation decay solver. The Bateman equation describes the abundances and activities of all members of the decay chain as a function of time, based on the decay rates and initial abundances. Beginning with one unit activity for the parent (e.g., 1 pCi), the fractional activity relationship of the progeny to the parent is determined as a function of time. Once the activity over time is known for all chain members, it is converted to an annual dose using the toxicity values and exposure parameters of the land use chosen by the user for each exposure route. See the equation below. The activities determined by the Bateman equation have been converted to an annual dose (mrem) as seen in the plot. The largest dose peak is identified as the peak annual dose (mrem).

    

    Where:
    C_dust is the activity determined by the Bateman equation solver for any given time point.

    The exposure duration for the chosen land use is used to establish a time interval spanning the peak start (PST) and end time (PET). The shaded blue column describes this interval. Within the blue column, the area under each chain member's curve is summed to give a total fractional unit dose for the exposure duration. To find this peak interval, the solver iterates across all time points from T₀ (now) through T_n (1E+12 yrs) with a quadratic function of activity and time.

    Once the PST and PET are known, the Peak DCC is calculated by normalizing the dose rates to the target risk across the peak exposure duration interval.

    The final piece in calculating the Peak DCC is to take the inverse reciprocal of the sum of average activities divided by the standard chain member DCCs (no decay).

    

    Where:

    BDCC_A-n are the standard BDCCs calculated without decay for each chain member
    n is the total number of radionuclides in the decay chain
    F_A-n are the average fractional activities of each chain member

    

    Where:
    ā_i is the average activity of the i^th chain member during the peak exposure duration
    A₀ is the initial unit activity of the parent

    

21. Are the future times given for some of the Peak BDCCs, that are thousands to billions of years, meaningful?

    Yes, they are meaningful in that the time frame offers understanding and knowledge for making decisions on waste disposal and site remediation. The dose standard that is determined to be an ARAR at the site may have a set time period for the dose assessment. If the dose-based ARAR does not have a set time period for the dose assessment, then the decision to utilize a time period other than Peak Dose may be made using professional judgement and justified based on the circumstances at the site (e.g., type of remedial action, radionuclides of concern).

22. What is the purpose of the calculator opening a new tab after I hit each retrieve button?

    Previous iterations of the calculator would display every page (i.e., main, site-specific input, and results pages) in the same browser tab after clicking the “Retrieve” button. Two issues arose from this single tab method.

    • Certain browsers would not remember the radionuclides in the pick list when using the browser back button to add forgotten radionuclides.
    • Certain browsers would not remember, or correctly display, the site-specific exposure parameters when using the browser back button to change values. This resulted in screening levels being calculated that did not match the input parameters. While the calculations would be correct, the results would not reflect the desired changes to the inputs after using the back button.

    Prior to the multiple tab method, users had to start from the initial calculator input page and manually enter radionuclides and then reenter their exposure parameters on the site-specific page, for each calculator run. With the new method, if a user wants to change the radionuclides being assessed or the exposure parameters being used, they simply go to the previous tab and make the necessary changes and click the “Retrieve (new window)” button. For users who have to build the same picklist over and over, having the radionuclides remembered in the calculator main page tab will save time. For users doing site-specific exposure assessments, the screening levels calculated will always match the input parameters because the browser back button is no longer an option.