United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Question 71: The "Class" column of 10 CFR 20 Appendix B

covers inhalation, but does not refer to ingestion. When

there are two ALIs for ingestion, how do these relate to

the "Class," since they really were based upon the f1 value

for gut absorption? (Note: The f1 value is the fractional

uptake from the small intestine to blood).

Answer: The ALIs for ingestion do not relate to the

"Class," which refers to the retention time in the

pulmonary region of the lung. There are two situations for

which there are two ALIs for ingestion. One is when the

ALI is determined by the non-stochastic dose to an organ.

In this case, the organ or tissue to which the limit

applies is shown, and the ALI for the stochastic limit is

shown in parentheses (for example, see ingestion ALI for

beryllium-10). The other case (and the case presumably in

question) is when different f1 values were used to

calculate the ingestion ALIs. For example, see the entry

for cobalt-60, for which the ingestion ALIs are 500 (on the

first line) and 200 (on the second line). These ingestion

ALI values have no relationship to the corresponding

"Class" on the same line (W on the first line and Y on the

second line). Rather, as explained in Federal Guidance

Report No. 11, these different ingestion ALIs are based on

two different f1 values: f1 = 0.05 for ALI = 500, and f1 =

0.3 for ALI = 200. As shown in Federal Guidance Report No.

11, Table 3, f1 = 0.05 for "oxides, hydroxides and trace

inorganic," and f1 = 0.3 for "organic complexed and other

inorganics." For inhalation of cobalt-60, f1 = 0.05 for

both "oxides, hydroxides, halides and nitrates" (class Y),

and "all others" (class W).

The following information on Federal Guidance Report No. 11

is provided for those not familiar with this document: The

title of this report is "Limiting Values of Radionuclide

Intake and Air Concentration and Dose Conversion Factors of

Inhalation, Submersion and Ingestion." The report is

subtitled "Derived Guides for Control of Occupational

Exposure and Exposure-to-Dose Conversion Factors for

General Application, Based on 1987 Federal Radiation

Protection Guidance." The report was published by the U.S.

Environmental Protection Agency (EPA) as report number

EPA-520 / 1-88-020 on September 1, 1988. The ALI and DAC

values in this report are used in Appendix B of the revised

Part 20. (References: 10 CFR 20 Appendix B, Federal

Guidance Report No. 11).

Page Last Reviewed/Updated Thursday, March 29, 2012