ArticlesRisk of cancer from diagnostic X-rays: estimates for the UK and 14 other countries
Introduction
Diagnostic X-rays are the largest man-made source of radiation exposure to the general population, contributing about 14% of total worldwide exposure from man-made and natural sources.1 However, although diagnostic X-rays provide great benefits, that their use involves some risk of developing cancer is generally accepted. The risk to an individual is probably small because radiation doses are usually low (typically <10 mGy), but the large number of people exposed annually means that even small individual risks could translate into a considerable number of cancer cases. Small risks are difficult to study directly in epidemio-logical studies.2 However, the risk from diagnostic X-rays can be estimated by extrapolating risk estimates from populations exposed to a range of doses, such as the Japanese atomic bomb survivors exposed at 0–4 Gy.1
In 1981, Doll and Peto3 estimated that about 0·5% of cancer deaths in the USA were attributable to diagnostic X-rays. Since then, use of this diagnostic method has increased in most developed countries.1 There is also wide variation in frequency of use from country to country.1 Our aim was, therefore, to estimate the risk of cancer on the basis of the annual use of diagnostic X-rays in the UK and in 14 other developed countries for which sufficient data are available.
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Methods
We estimated the cumulative risk, to age 75 years, that an individual will develop a cancer caused by diagnostic X-rays,4 using models for the risk of incident cancer after radiation exposure, estimates of the average annual frequency of exposure for each type of diagnostic X-ray, estimates of the organ-specific radiation doses delivered by each X-ray type, and cancer incidence and all-cause mortality rates for the 15 populations being studied—ie, UK, Australia, Canada, Croatia, Czech Republic,
Results
We estimate that diagnostic X-ray use in the UK causes 0·6% of the cumulative risk of cancer to age 75 years in men and women (table 2), equivalent to 700 cases per year for both sexes combined. Of the nine cancers listed in table 2, bladder cancer accounted for the largest number of radiation-induced cases per year in men, followed by colon cancer and leukaemia. In women, of the nine listed cancers, colon cancer made the greatest contribution to the annual total followed by cancers of the lung
Discussion
Radiation is one of the most extensively researched carcinogens, but the effects of low doses are still somewhat unclear. Our estimates are based on the assumption that small doses of radiation can cause cancer. The weight of evidence from experimental and epidemiological data does not suggest a threshold dose below which radiation exposure does not cause cancer.20 If there is no threshold then diagnostic X-rays will induce some cancers.
To calculate our estimates, we had to make several other
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