A statistically determined correlation between radioactive fallout from the Chernobyl accident and an increase in the number of cases of cancer in the exposed areas in Sweden is reported in a study by scientists at Linköping University, Örebro University, and the County Council of Västernorrland County.

It is the first study demonstrating such a correlation. It is being published in the scientific journal Journal of Epidemiology and Community Health.

A rise in cancer cases related to the Chernobyl accident has previously been established in studies carried out in the former Soviet Union.

After the nuclear power accident at Chernobyl on April 26, 1986, some of the radioactive emissions were carried by the wind to Sweden. Heavy rain caused a relatively large amount, about 5 percent of the Cesium-137 released in the disaster, fell on Sweden, above all along the coastal area of Northern Sweden and northern central Sweden. The fallout in Sweden was unevenly distributed and, compared with the areas close to the nuclear power station at Chenobyl, considerably less. Knowledge of the possible consequences of radioactive fallout on health prompted a number of measures to be taken to reduce these consequences at the time of the Chernobyl accident.

The study now being published aims to help answer the question of whether there is increased cancer morbidity that can be tied to this fallout. The study divides the parishes in the seven northernmost Swedish counties into six classes on the basis of ground coverage of cesium 137. Most of the parishes in the seven counties, 333 out of 450, were impacted by the fallout. One class comprising 117 parishes received no fallout, and the individuals in these parishes were used as a control group. Those people aged 0-60 who were resident in the counties in question and who had the same address on December 31, 1985 and December 31, 1987, were monitored for development of cancer. At the outset of the study 1,143,182 individuals were included, and 22,409 cases of cancer were registered during the years 1988 through 1996.

There is a statistically established correlation between the degree of fallout and an observed rise in the number of cancer cases. The increase involves all types of cancer in the aggregate. On the other hand, no clear effect can be seen for individual forms of cancer, not even for those types that have been regarded as especially susceptible to radiation, such as leukemia or thyroid cancer.

It is remarkable that an increase in cancer morbidity could have occurred after such a relatively short time following the accident, but just such a short time period has been described for groups exposed to radioactive radiation. If the correlation found here is not a product of chance, or other unknown disturbances than those corrected for in the analysis, then one possible explanation is that the radiation hastened the growth of already established tumors in their early stages, rather than that new tumors occurred.