Thyroid cancer incidence due to technogenic exposure in childhood

Thyroid cancer incidence was studied in the cohort of residents of Ozyorsk and Kyshtym, the nearest upwind cities to the Mayak Production Association (Mayak PA), Russia's first plutonium production facility, which has been in operation since 1948. Radioactive contamination of areas around the Mayak PA were from unmonitored releases of inert gases produced by industrial reactors and also from the release of uranium fission products from a radiochemical plant stack where irradiated uranium blocks were refined. Iodine-131 (131I) was the main contributor to the technogenic dose from atmospheric releases. Routine monitoring of gaseous releases began in the mid-1960s, when a gas purification system was perfected. Children were a critical group due to their higher radiosensitivity and specific diet (dairy products and vegetables). Both cities maintain Registries containing over 100,000 individuals born from 1934-2006. Among this group, more than 100 cases of thyroid cancer were registered during 1948-2009. The relative risk of thyroid cancer incidence is 1.5 times higher than in the Chelyabinsk.