Answer to Question #9921 Submitted to "Ask the Experts"

Is there a minimum ionizing radiation level at which the radiation symbol must be used? For example, could the symbol be used on a banana (it has ⁴⁰K and produces ~4 microrem of radiation)? If not a single banana, then how many bananas? If not bananas at all, then what are the standards of usage for the radiation symbol?

The reason I'm asking is that I'm putting together a radiation awareness training course for some of our employees, and want to correctly use the radiation symbol in the presentation and discussion.

If you review the U.S. Nuclear Regulatory Commission (NRC) Regulations or Agreement state regulations, if these apply to you, you will find specific recommendations and requirements for posting specific locations with appropriate signs that contain the radiation warning symbol. Such posting is required for certain radiation levels and for places where radioactive materials are present.

The sections of the NRC regulations that apply are 10 CFR 20.1901 through 10 CFR 20.1905, which can be accessed easily on the web. In general, if radiation levels exceed 0.05 mSv in one hour at 30 cm from the radiation source, posting of the affected area or room is required; the sign should specify the type of radiation area (Radiation Area, High Radiation Area, or Very High Radiation Area), depending on what the dose rate is (see appropriate definitions of the areas in 10 CFR 20.1003). Posting is also required for airborne radioactivity areas. Separate posting is also required for rooms and containers that hold licensed material in excess of specified values or concentrations. You can review the details of the requirements for the signage, including the wording that is required, in the cited NRC regulations.

The 10 CFR 20 NRC regulations are intended to apply to radioactive material licensed by the NRC. The use of signage, including the radiation symbol, is then associated with the possession and use of licensed radioactive material. A similar situation prevails for agreement states, except that their regulations may also apply to radiation from some machines and some radioactive materials not specifically controlled by the NRC. Food products containing nominal amounts of naturally occurring radionuclides, as is the case with the bananas you cite, are not licensed or controlled by radiation control programs of either the federal government or the state governments. It is not a legitimate use of the radiation symbol and associated signage to place the signs/symbols on such items or to use them in areas where radiation levels or radioactive materials are not a concern. To my knowledge, the NRC regulations do not have a specific prohibition against the inappropriate or frivolous use of the radiation symbol/sign, but such misuse is generally discouraged by regulating groups and licensees. Licensed facilities often have internal controls and prohibitions against the inappropriate use of the radiation warning symbol.

The Food and Drug Administration and the U.S. Environmental Protection Agency do have some jurisdiction regarding public food that might become contaminated with manmade and/or technologically enhanced natural radionuclides, but the use of the radiation warning symbol is not an issue of concern. 

I hope your radiation awareness presentation is well received.

George Chabot, PhD