622 Childhood cancer incidence in relation to distance from the former nuclear testing site in Semipalatinsk, Kazakhstan

There are few data on Cancer risk fullowing atmospheric nuclear explosions. Rates of childhood cancer between 1981 and 1990 in the four administrative zones of Kazakhstan were studied to assess the relationship, if any, with distance from nuclear testing sites. Risk of various cancers among children aged 14 years and younger were estimated in relation to distance from (I) a site where testing in air was perfurmed before 1963, (2) a site where underground testing took place thereafter, and (3) a reservoir, known as “Atom Lake”, created by four nuclear explosions in 1965. Risk of acute leukaemia rose significantly with increasing proximity of residence to the testing areas, although the absolute value of the risk gradient was relatively small. The relative risk for those living less than 200 km from the air-testing site was 1.76 compared with those living 400 km or more away from the site. Similar relative risks were observed fur the underground site and “Atom Lake”. There was also some evidence of increased risk of brain tumours in association with proximity to the test sites. In two of the fuur zones studied, there was substantial regional variation in acute leukaemia rates which was not attributable to distance from the test site. The findings may be affected by potential confounders, notably urban/rural status and ethnic factors but tend to confirm an association with increased risk of childhood leukaemia and exposure to radioactivity from atmospheric nuclear explosions.