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X-Ray Equipment in Medical Diagnosis Part A: Recommended Safety Procedures for Installation and Use - Safety Code 20A

Appendix I - Recommended Dose Limits of Ionizing Radiation

For the purpose of radiation protection, individuals may be classified in one of two categories: those exposed to radiation from man-made sources during their work (radiation workers), and others. The recommended dose limits are given for both categories in the following table. These dose limits are based on the latest recommendations of the International Commission on Radiological Protection (ICRP) as specified in ICRP Publication 60.

It must be noted that the dose limits for radiation workers apply only to irradiation resulting directly from their occupation and do not include radiation exposure from other sources, such as medical diagnosis and background radiation.

1. It is emphasized that any irradiation may involve some degree of risk and the levels suggested in this Appendix are maximum recommended values. All doses should be kept as low as reasonably achievable and any unnecessary radiation exposure must be avoided.
2. ICRP does not recommend discrimination in the dose limits between men and women of reproductive capacity, if the dose is received at an approximately regular rate.
3. For occupationally exposed women, once pregnancy has been declared, the foetus should be protected from x-ray exposure by applying a dose limit of 2 mSv to the surface of the woman's abdomen for the remainder of the pregnancy. For women who are also occupationally exposed to nuclear activities or substances, the Atomic Energy Control Board recommends an effective dose limit of 4 mSv for the remainder of the pregnancy from all the above sources.
4. For technologists-in-training and students, the recommended dose limits for members of the public should apply.
5. ICRP does not recommend different limits for individual organs. For occupationally exposed workers, ICRP believes that deterministic effects will be prevented by applying an equivalent dose limit of 500 mSv in a year to all tissues except the lens of the eye, for which it recommends a limit of 150 mSv in a year.
6. For the skin, the equivalent dose is averaged over its whole area. In situations where deterministic effects are possible, the recommended equivalent dose limit for the skin is 500 mSv and is averaged over areas of no more than 1 cm². This limit applies to the skin of the face and the hands.
7. ICRP limits allow, in special circumstances, a higher value of dose than is allowed in a one year period, as long as the average dose over a five year period is not greater than the annual limit. This higher value is 50 mSv for occupationally exposed personnel. However, in mammography, there is no circumstance where such provision should apply.
8. Some provincial jurisdictions may have recommended dose limits for some workers. Consultation with the proper agency may be required to determine the recommended dose limits in effect in a particular jurisdiction.