The following table lists the recommended annual limits for workers on oral and inhalation intakes (ALI) for selected radionuclides based on the occupational radiation protection guidance of the International Commission on Radiological Protection (Refs. 1 and 2). An intake of one ALI corresponds to an annual whole body dose of 0.02 Sv (2 rem).
The ALI is expressed in the SI unit of activity, the becquerel (Bq), and in the conventional unit, the microcurie (µCi); 1 µCi = 3.7⋅104 Bq for both inhalation intakes (inh) and oral intakes (orl).
The chemical form of inhaled radionuclides is, in most instances, stated in terms of the rate of absorption to blood from the lungs and the fractional absorption from the small intestine. Types F, M, and S denote chemical forms that are absorbed from the lungs at rates characterized as fast, moderate, and slow, respectively. The time to absorb 90% of the deposited radionuclide, in the absence of radioactive decay, corresponds to about 10 minutes, 150 days, and 7000 days for Type F, M, and S compounds, respectively. Type F compounds can be considered to be more soluble than M or S, S being the most insoluble. Chemical form consideration for ingestion is specified by the fractional absorption from the small intestine, denoted as f1. The f1 values range from 10–5 to 1. Higher fractional absorption is associated with greater solubility of the compound.
The notation 1.1E+13 means 1.1·1013. Column definitions for the table are as follows.
Column heading | Definition |
Radionuclide | Symbol for radionuclide; radionuclides are listed in order of increasing atomic number |
Physical half-life | Half-life of the radionuclide; y = years; d = days; h = hours |
Chemical form f1 | Chemical form consideration for ingestion as specified by the fractional absorption from the small intestine, denoted as f1; see discussion above |
ALI(inh)/Bq | Annual limit intake for inhalation, in units Bq |
ALI(inh)/μCi | Annual limit intake for inhalation, in units μCi |
ALI(orl)/Bq | Annual limit intake for oral ingestion, in units Bq |
ALI(orl)/μCi | Annual limit intake for oral ingestion, in units μCi |
Radionuclide | Physical half-life | Chemical form f1 (inh) | ALI(inh)/Bq | ALI(inh)/μCi | Chemical form f1 (orl) | ALI(orl)/Bq | ALI(orl)/μCi |
Continued on next page... | |||||||
3H | 12.3 y | HT gas | 1.1E+13 | 3.0E+08 | 1.000 | 1.1E+13 | 3.0E+08 |
HTO vapor | 1.1E+09 | 3.0E+04 | |||||
11C | 0.340 h | CO | 1.7E+10 | 4.5E+05 | 1.000 | 8.3E+08 | 2.3E+04 |
CO2 | 9.1E+09 | 2.5E+05 | |||||
Organic compounds | 6.2E+09 | 1.7E+05 | |||||
14C | 5730 y | CO | 2.5E+10 | 6.8E+05 | 1.000 | 3.4E+07 | 9.3E+02 |
CO2 | 3.1E+09 | 8.3E+04 | |||||
Organic compounds | 3.4E+07 | 9.3E+02 | |||||
18F | 1.83 h | F 1.000 | 3.7E+08 | 1.0E+04 | 1.000 | 4.1E+08 | 1.1E+04 |
M 1.000 | 2.2E+08 | 6.1E+03 | |||||
S 1.000 | 2.2E+08 | 5.8E+03 | |||||
22Na | 2.60 y | F 1.000 | 1.0E+07 | 2.7E+02 | 1.000 | 6.3E+06 | 1.7E+02 |
24Na | 15.0 h | F 1.000 | 3.8E+07 | 1.0E+03 | 1.000 | 4.7E+07 | 1.3E+03 |
32P | 14.3 d | F 0.800 | 1.8E+07 | 4.9E+02 | 0.800 | 8.3E+06 | 2.3E+02 |
M 0.800 | 6.9E+06 | 1.9E+02 | |||||
35S | 87.4 d | Inorganic compounds | |||||
F 0.800 | 2.5E+08 | 6.8E+03 | 0.800 | 1.4E+08 | 3.9E+03 | ||
M 0.800 | 1.8E+07 | 4.9E+02 | 0.100 | 1.1E+08 | 2.8E+03 | ||
Vapor | 1.7E+08 | 4.5E+03 |