Tuesday, April 12, 2011

Radiation, Chernobyl, and the Japanese burden of cancer


The New York Times today reports that the nuclear disaster in Japan is on par with the 1986 Chernobyl explosion (see story). It is appropriate that we consider the impact this will have on disease. In a rigorous review of the epidemiologic evidence following the Chernobyl nuclear accident, Cardis and Hatch provided an update on the impact of that explosion on millions of people in Europe (see article). They document the well-known exposure for children and adolescents from Chernobyl fallout and the associated increase in thyroid cancer. The greatest increase in risk is seen in those youngest at exposure. Deficiency in stable iodine may exacerbate this risk. The data on thyroid cancer risks to other age groups are less definitive.  Studies have also reported increases in both the incidence and mortality from non-thyroid cancers and other diseases. Study of cleanup workers provides evidence of an increased risk of leukemia and other hematologic malignancies. These workers also have increased risk of cataracts and a suggested increased risk of cardiovascular disease following low dose exposures.

In the Times story an accompanying graphic gives a vivid presentation of the distribution of exposures. They present exposure through the air, soil, and water, Over the coming years, given the clear causal relation between radiation exposure and cancer risk, Japan too will experience an increase in thyroid and other cancers. This will be most clearly seen in the first 20 years as an increase in thyroid cancer. Previous follow-up of atomic bomb survivors, also from Japan,  shows that higher radiation exposure in childhood leads to increased risk of breast cancer many years later.

The overall impact of even low-dose radiation a known carcinogen, on the cancer burden in the population is unquestionable. The clear exposure as a consequence of the Japanese tragedy will lead to excess cancers in the years ahead. More rigorous efforts to control exposure in future disasters must be a public health preparedness priority.

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