Answer to Question #10942 Submitted to "Ask the Experts"

Category: Radiation Basics — Radiation Effects

The following question was answered by an expert in the appropriate field:

Q

I have heard many doctors say that women are more sensitive to radiation than men are. Can you explain why this happens?

A

As a general observation, the statement you ascribe to the doctors is correct. If you look at the risk of ionizing radiation exposure to women of all ages averaged together compared to the risk to men of all ages averaged together, you will find that the risk of incidence of cancers of all types and serious health impacts are somewhat higher for the women than for the men, with the overall lethality risk for women being approximately 35 percent greater than that for men (based on data in Table A4.1.9 of International Commission on Radiological Protection [ICRP] Publication 103, ICRP, 2007).

One must be careful, however, in attempting to interpret the significance of such a difference when a specific individual is involved. This is the case because the possible negative effects of radiation exposure to an individual depend on many factors, including not only the gender of the individual, but also the age of the individual, his/her overall health, possible modifying genetic factors, the part(s) of the body being irradiated, and other possible mitigating factors. Considering only gender (for individuals of all ages averaged together), for men the risks of lethality (from cancer) resulting from irradiation of the liver and the colon are each about twice as great as the risks from irradiations of the same organs in women. For women, the greatest impacts on specific tissues compared to the effects on men result from irradiation of the breast and the thyroid gland, the latter having an adjusted lethality risk about six times greater than that for men and the breast risk being substantially greater (ICRP lethality-adjusted risks in lethalities per 10,000 individuals, each receiving 1 Sv of radiation dose to the affected tissue are 64 and 0 for women and men, respectively).

Another consideration that must be taken into account in the case of irradiation of women is whether the woman is pregnant. In such cases, consideration of risk must also include the possible effects of radiation on the developing embryo or fetus. This is important but does not specifically affect the risk to the woman herself, with the possible exception that changes in hormonal balance during pregnancy could possibly have some influencing effect on radiation sensitivity.

In fact, it has been postulated that hormonal differences between women (pregnant or not) and men may have some impact on the enhanced radiosensitivity of women. Other influencing factors may also be responsible for the differences in sensitivity between men and women. Some types of cancer are naturally more prevalent in women than in men, independent of any added radiation exposure, and it is possible that added radiation exposure may act as a promoting agent that increases the frequency of cancer. For example, thyroid cancer is about three times more common in women than in men, without added radiation exposure, and a factor of 5 to 6 is associated with added radiation exposure. Beyond such possibilities, we do not have a definite answer as to why radiation sensitivities differ between men and women.

For routine radiation protection purposes, adopted by most countries, the radiation risks for men and women have been averaged together to obtain risk factors that have been used in establishing exposure standards and recommendations. This approach is considered adequate for purposes of general radiation protection, but such standards and recommendations may not be very useful for assessing risks to specific individuals under specific conditions. It is important to keep this in mind, especially in situations in which individuals may have been exposed to high doses of radiation that could have a large negative health impact. In such instances it may be necessary to consider the gender, age, parts of the body irradiated, and other mitigating factors in making a risk assessment.

I have probably gone on here longer than I should have and longer than you may require, but I believe it is important to understand that the radiation risk factors that we often use are based on certain simplifying assumptions and that accurate assessments of actual risk to a specific individual may require incorporation of additional considerations.

George Chabot, PhD

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