The United States (FDA and EPA) and the World Health Organization (WHO) have issued standards that limit the amount of contamination in food, water, and air.

Table 3 provides a summary of standards for environmental and occupational exposures to I-131. The FDA food concentration guidelines both (a) restrict the flow of contaminated food out of an affected area into the regional or global food supply and (b) set limits on local consumption of affected food and water. If limits are exceeded for the local population, uncontaminated food should be provided from outside the affected area. This also applies to drinking water with I-131 levels above EPA limits.

Occupational limits for radionuclide exposure address ingestion, inhalation, and external exposure and are set by the Nuclear Regulatory Commission (NRC) for NRC licensees and by the Department of Energy for DOE facilities. The NRC limits for I-131 are as follows:

• 2 ×10^-8 µCi/mL (for occupational air exposure)
• 2 ×10^-10 µCi/mL (for effluent air to which the public could be exposed)
• 1 ×10^-6 µCi/mL (in effluent water), and
• 1 ×10^-5 µCi/mL (for monthly average releases to sewers from medical facilities).

These NRC limits are intended to ensure that no worker exceeds 50 mSv (5 rem) of I-131 to the whole body or 500 mSv (50 rem) to the thyroid, and that no member of the public exceeds 1 mSv (0.1 rem) to the whole body.

Table 3. Summary of Recommended Maximum Concentrations of I-131 in Specific Media and for Occupational Exposure