As a result of atmospheric nuclear tests at the Semipalatinsk test site 'Polygon', adjacent territories were contaminated by radionuclide fallout. The population of some districts in the Semipalatinsk oblast were exposed to elevated levels of radiation. Contamination and exposure mostly resulted from early atmospheric tests. The radiological situation of the Semipalatinsk oblast is described. Effective dose estimates due to external and internal exposure attributable to the 1949 and 1953 tests in villages near the Polygon range from 70 mSv to 4470 mSv.

Nuclear bomb testing was carried out under conditions of secrecy at the Semipalatinsk test site (STS) between 1949 and 1962. The first test on August 29, 1949 unexpectedly contaminated villages to the northeast, both in Kazakhstan and the Altai region of Russian Siberia. In Kazakhstan, extensive measurements were made of fallout concentration on the ground and there were efforts, which were not always successful, to avoid future fallout contamination of population centers. As soon as evidence appeared of excess leukemia risk among the survivors of the atomic bombings of Hiroshima and Nagasaki and among medically exposed populations, attention turned to potential health consequences in the population near the STS. In 1957, a secret medical institution, specializing in oncology and designated 'Dispensary Number 4', was established in Semipalatinsk to perform diagnostic and clinical ward, to collect data on the population's health status in the Semipalatinsk oblast, and to collect various material for possible future analysis. The Kazakh Research Institute for Radiation Medicine and Ecology (KRIRME), which was founded in 1991, inherited the functions and the formerly top secret health archives of Dispensary No. 4. These archival data including the information on the KRIRME study population of residents of heavily exposed and less exposed villages in the oblast, are the basis for a number of international collaborative projects focussed on fallout exposure and possible health effects in the exposed population.

Since 1956, cancer incidences have been analysed in several rayons of the Semipalatinsk oblast, with cross-sectional analyses being conducted every 5 years. Data on different tumor localizations were recorded within a heavily contaminated so-called main area of nine villages (estimated average effective equivalent dose about 2000 mSv) and a so-called control area (estimated average effective equivalent dose about 70 mSv), each including approximately 10000 persons. Up to 1970, the excess cancer incidence in the exposed villages was observed to have increased; after 1970, a decrease was noted, followed by a second increase in the late 1980s. The main sites of excess cancer included the esophagus, stomach, and liver. Up to 1970, the esophagus cancer incidence was predominant, but it decreased thereafter, while the incidence of stomach and liver cancers increased. The second peak of excess cancer rates was mainly due to lung, breast, and thyroid carcinomas.

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