DCC What's New
The What's New section keeps users informed of toxicity value changes, exposure parameter changes, isotope-specific parameter changes, and any equation format changes. Please check this site frequently to be advised of any recent changes.
- Updates to soil gamma shielding factors (GSFo and GSFb) have been implemented in the calculator. All GSF values were recalculated using MCNP to achieve a lower error and correct the non-linear regression issue for some isotopes. Each common Superfund isotope's full spectrum of emission energies was rerun. The monoenergetic values for low energy emissions were rerun for all other isotopes. Secondary photons produced during positron emissions were also included. The technical memorandum is still being updated, but the new GSF values can be found here.
- While running the user provided option in site-specific mode, the calculator was showing duplicate records for C, H, Hg, I, Ni, Ru, S, and Te elemental isotopes. These duplicate records have been removed.
- The soil gamma shielding factor (GSFo and GSFb) database has been updated:
- GSFo and GSFb values for cover thicknesses 10cm - 100cm were swapped between isotopes and their respective metastable isotopes. This has been corrected.
- Some GSFo and GSFb values for non-gamma emitters were defaulted to 1 for all cover thicknesses. The values for these isotopes were changed to 0 for all cover thicknesses, as the minimum cover depth of 10cm would block all alpha and beta radiation. A list of the isotopes affected can be found here.
- The isotopes listed below are also non-gamma emitters that previously had shielding factor values other than 1. The GSFo and GSFb values for these isotopes have also been set to 0 for all cover thicknesses. It is possible that progeny are gamma emitters, as in the case of Cs-137 with its progeny Ba-137m.
- Bi-210, Bk-249, Cs-137, Pm-147, Po-210, Pr-143, Pu-241, Tc-99, Y-90, Zn-69
- When the secular equilibrium DCC output option is selected, the DCC Calculator now gives the option to show the individual progeny contributions for the DCC (and risk) output.
- The soil gamma shielding factor (GSFo and GSFb) database has been updated:
- Zr-97 GSFo values have been added for the 2 - 10 m cover depths.
- Ra-226 and Ra-228 GSFo values have been added for the 0 to 100 cm cover depths. These missing values impacted any secular equilibrium DCC and risk outputs that included Ra-226 or Ra-228 as parents or progeny.
- For the soil volume source thickness, the GSFo values have been corrected to match the supporting documentation for the 0 to 100 cm cover depths. The values incorporated represent a source depth of 1 meter to simulate infinite soil volume; previous values were based on a 2 meter simulation depth.
- New soil-to-plant transfer factors are available for carbon isotopes. See section 2.5.4 in the User's Guide.
- The +D and +E isotopes have been removed from the selection list. Now, a user may select the 'Assume secular equilibrium' to see PRG output for the entire chain.
- In the resident, farmer, and indoor worker soil external exposure equations, a new variable has been added (GSFb) to account for the gamma shielding provided by clean soil cover under a building. It is combined with GSFi, the shielding provided by the building, to reduce exposures to receptors inside a building that is on top of clean soil over contaminated soil.
- Previously, produce intake rates were based on general fruit and vegetable consumption rates. Now, the produce intake rates are derived from 22 individual produce items, found in the 2011 Exposure Factors Handbook, that contribute to the overall produce ingestion DCC. Mass loading factors (MLFs) were also improved, from a single MLF that was applied to all produce to 22 individual MLFs that correspond with the 22 individual produce items for the new produce intake rates. In site-specific mode, users will now be able to select additional animal products including Goat Milk, Sheep Milk, Goat Meat, and Sheep Meat, which are not included in the default animal product DCCs. Users will also be able to select Rice and Grains, which are not included in the default produce DCC. Formerly, the transfer factors used in this risk assessment tool were specific to element only. Now, the transfer factors are element, climate zone, soil type, and produce specific. For more detailed information, Biota Modeling in EPA's Preliminary Remediation Goal and Dose Compliance Concentration Calculators explains where these new intake rates, MLFs, and transfer factors were sourced and how they will be applied to the DCC calculator. This file is engineered for 2 sided printing.
- The MCL document was modified to remove +D and +E isotopes.
- New inhalation Risk and Dose Coefficients are avilable for Rn-222, Rn-220, Bi-212, Bi-214, Pb-212, Pb-214, and Po-218.
- The ingestion rate while swimming was updated based on Table 3.5 in EFH 2011. The recommended values of 120 ml/hr for children and 71 ml/hr for adults are now used.
- Additional source depth-specific soil gamma shielding factors (GSF) are now given for cover depths of 2 to 10 meters. The values are presented in this appendix.
- The MCL concentrations used in the soil to groundwater land use scenario have been updated.
- This calculator follows the recommendations in the OSWER Directive concerning use of exposure parameters from the 2011 Exposure Factors Handbook. The OSWER Directive concerning use of exposure parameters from the 2011 Exposure Factors Handbook recommends an adult body weight of 80 kg. While body weight is not directly used in the DCC equations, the biota intakes in the Exposure Factors Handbook are given in g/kg body weight - day. New child and adult intake rates from the 2011 Exposure Factors Handbook were added for produce, milk, beef, pork, fish, eggs, and poultry for the farmer and resident. See the User Guide for details on biota intake derivations. This spreadsheet shows how the child and adult intakes and indoor and outdoor exposure times were derived from the data presented in the 2011 Exposure Factors Handbook.
- The decay function was added to the resident, recreator, and farmer biota PRGs that are back-calculated to soil.
- New dose coefficients (DCFs) have been programmed that were derived following FGR 12 and 13 using the updated isotope list from ICRP 107. DCFS used are provided by the Center for Radiation Protection Knowledge. The main report is Calculations of Slope Factors and Dose Coefficients and the tables of DCFs are in a separate appendix.
- The resident (and farmer) tapwater scenario now includes the contribution from consuming produce irrigated with contaminated tapwater. This is analgous to the resident soil scenario that includes contribution from consuming produce grown in contaminated soil.
- Immersion was added to the tap water and recreational scenarios to address external exposure from gamma and beta emitters.
- The Agricultural uptake models were completely changed. Now users can back calculate protective concentrations in water and soil as well as the produce itself. The water concentrations also now include irrigation of crops.
- Farmer output now provides an interactive graph that depicts PRGs for when both soil and water are contaminated.
- New Biota transfer factors from the IAEA Technical Report Series No. 472 have been programmed.
- A forward dose assessment option was added to the calculator page. By selecting this option, the user is asked for media concentrations, and the dose is returned using DCC equation inputs.
- Recreator scenario added for soil/sediment, surface water, and generic game (land and fowl). Because there are very few default values for exposure parameters, the user must provide most of the exposure inputs.
- Source depth-specific soil area correction factors (ACF) are now provided. Unique ACFS are now given for the various dose coefficients (ground plane, 1 cm, 5 cm, 15 cm, and infinite depth). For further information on the derivation of the isotope-specific/area-specific ACF values for 2-D areas, see the Center for Radiation Protection Knowledge ACF report and appendix containing +D and +E values.
- Source depth-specific soil gamma shielding factors (GSF) are now given for the various dose coefficients (ground plane, 1 cm, 5 cm, 15 cm, and infinite depth) and various soil cover depths. The Center for Radiation Protection Knowledge has provided GSFo values here and appendix containing +D and +E values.
- The radionuclide decay chains, provided in the calculator output, have been updated to reflect new decay information provided in ICRP 107. In addition to tabular results, a visual diagram is provided depicting the branching fractions.
- Two construction worker scenarios were added for the assessment of particulates emitted into the air from standard vehicle traffic as well as activities such as dozing, grading, tilling, and excavating.
The calculator results, presented in Becquerels, were modified to correct a units conversion problem.
New tables were generated to correct the use of the wrong gamma shielding factor for worker soils.
New tables were generated to reflect the changes made in June.
- An ambient air scenario was added that evaluates PRGs with and without radioacive decay, identical to the ambient air scenario in the radiological BPRG and SPRG calculators.
- A composite worker scenario was added to evaluate Industrial PRGs that is identical to the RSL website.
- The indoor air dilution factor was removed from the indoor component pieces of the resident, worker and farmer inhalation PRG scenarios to be consistent with the RSL website.
- The tapwater equations were modified to have the ingestion rate age-adjusted between children and adults consistent with the RSL website.
- The ACF parameter was made isotope-specific and specific for eight different areas (slab sizes) similar to the SPRG.
- Soil PRG equations for external exposure were added for ground plane, 1cm, 5cm and 15cm slope factors similar to the SPRG.
- Exposure times for the resident and workers in the PRG equations were made identical to the RSL website.
The half-life of Am-242m was changed from 152 to 141 years.
The default values for ETowo (Outdoor Worker Exposure Time Outdoor) and ETiwi (Indoor Worker Time Indoor) have been changed back to 0.33 from 1.0. This change is because the external exposure route was inadvertently affected. To sustain the desired intention of a worker being exposed 8 hours of the 8 hour worker day, the inhalation rate for workers was changed to 60 m3/day (this reflects an hourly inhalation rate of 2.5m3/hour).
The default values for ETowo (Outdoor Worker Exposure Time Outdoor) and ETiwi (Indoor Worker Time Indoor) have been changed from 0.33 to 1.0. This change reflects the desired intention of a worker being exposed 8 hours of the 8 hour worker day.
- 100 yr (+D) and 1000 yr (+E) values have been added to the database for those nuclides where applicable.
- Download tables have been updated.
- Decay has been added to the Dose Cleanup Concentration equations.
- Download tables are now available for Bequerels.
New pathways have been added to the Agriculture Scenario. Ingestion of Swine, Ingestion of Poultry, and Ingestion of Eggs are now included. Also, a downloadable table of bio-transfer factors is available in the Download Area.
The default produce consumption rates have been revised. The following changes have been made:
- Adult Fruit -- 20.5 kg/yr
- Child Fruit -- 5.4 kg/yr
- Adult Vegetables -- 10.4 kg/yr
- Child Vegetables -- 3.8 kg/yr
Note to Users: The ICRP Rule 60 dose conversion factors are now available on Superfund's Radionuclide Dose Levels for ARAR Compliance website. Please check out the DCC Calculator or the Download Area for values.