Answer to Question #1572 Submitted to "Ask the Experts"

Q

According to BEIR V, what is the occupational dose limit (per year) for someone who works with radiation in Canada and what is the risk of an average Canadian of dying of cancer?

A

BEIR V summarizes what is known about radiation biology, radiogenic cancer induction, and radioepidemiology and provides risk estimates and a discussion of radiogenic cancer induction. It is important to note that BEIR V does not provide recommendations on occupational exposure limits. Therefore, government agencies (such as, in the United States, the Nuclear Regulatory Agency) use various inputs, such as BEIR V and other recommendations from international agencies (such as the United National Scientific Committee on Effects of Atomic Radiation [UNSCEAR] and the International Commission on Radiation Protection [ICRP]) to develop its regulations.

Occupational exposure limits in the United States are based upon ICRP-26 and 30. The NRC provides its occupational regulations in Title 10, Code of Federal Regulations, Part 20 (that is, 10 CFR 20). They are as follows (in general): §20.1201 Occupational dose limits for adults. (a) The licensee shall control the occupational dose to individual adults, except for planned special exposures under §20.1206, to the following dose limits: (1) An annual limit, which is the more limiting of— (i) The total effective dose equivalent being equal to 5 rems (0.05 Sv) or (ii) The sum of the deep-dose equivalent and the committed dose equivalent to any individual organ or tissue other than the lens of the eye being equal to 50 rems (0.5 Sv). (2) The annual limits to the lens of the eye, to the skin, and to the extremities, which are: (i) A lens dose equivalent of 15 rems (0.15 Sv) and (ii) A shallow-dose equivalent of 50 rems (0.50 Sv) to the skin or to any extremity. There are also limits for inhalation, such as the derived air concentration (DAC) and annual limit on intake (ALI) values which are presented in table 1 of Appendix B to 10 CFR Part 20 and may be used to determine the individual's dose (see §20.2106) and to demonstrate compliance with the occupational dose limits. In addition to the annual dose limits, the licensee shall limit the soluble uranium intake by an individual to 10 milligrams in a week in consideration of chemical toxicity (see footnote 3 of Appendix B to part 20). [see 56 FR 23396, May 21, 1991, as amended at 60 FR 20185, Apr. 25, 1995] While the risk for cancer mortality in Canada is probably similar to that in the United States, which in general is taken to be about 1 in 5, the risks of developing specific types of cancers varies greatly. Your best bet is to contact the Canadian government for specifics on the Canadian regulatory limits for occupational exposure in the geographical location of interest.

Two organizations that will be of help are the Canadian Radiation Protection Association (similar to the Health Physics Society) and the Canadian Nuclear Safety Commission (similar to the Nuclear Regulatory Commission) to get specifics on the Canadian government requirement for the annual occupational effective dose and risks associated with cancer.

Cynthia G. Jones, PhD

Richard R. Brey, CHP, PhD