BDCC Frequently Asked Questions (FAQ)

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?
  4. How should dose conversion factors be used?
  5. What dose-based radiation standards may be applicable or relevant and appropriate requirements (ARARs)?
  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 do the ingestion and external BDCC values compare to the DCC values for soil?
  13. What is the preferred citation for information taken from this website?
  14. Where else can I go for toxicity studies (values) not on this site?
  1. What are BDCCs?
  2. 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.

  3. What are BDCCs used for?
  4. 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 risks 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.

  5. What are radionuclide dose conversion factors?
  6. 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 soil, air, water, or foodstuffs 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.

  7. How should dose conversion factors be used?
  8. 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).

  9. What dose-based radiation standards may be applicable or relevant and appropriate requirements (ARARs)?
  10. 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.

  11. How do BDCCs differ from cleanup standards?
  12. 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.

  13. How often do you update the BDCC Table?
  14. The recommended BDCC database is typically updated when new toxicity values are presented by the EPA. This is generally done monthly; however, there may be times when more than one month passes without the release of updated toxicity values. Please take note of the "What's New" page to identify when toxicity values are updated.

  15. Can I get a copy of a previous BDCC table?
  16. 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.

  17. What ages and exposure routes are considered in each land use?
  18. 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.

  19. How can I select more than one isotope at a time in the BDCC Search page?
  20. 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.
  21. How are the BDCC results converted to a mass basis?
  22. 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.


  23. How do the BDCC ingestion and external values for settled dust compare to the DCC values for soil?
  24. 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.
  25. What is the preferred citation for information taken from this website?
  26. United States Environmental Protection Agency. Dose Compliance Concentrations for Radionuclide Contaminants in Buildings at Superfund Sites. (insert date accessed and url).

  27. Where else can I go for toxicity studies (values) not on this site?
  28. 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.