Thyroid neoplasia in mures county after Chernobyl accident: 10 years follow-up

We hereby report the results of an epidemiological approach regarding thyroid cancer morbidity in Mures county over a long period of rime, before and after the accident, in order to establish a casual relation between the supplementary exposure and health risks on population. Thus, in the first years after 1986, in Mures county the average value of the Effective Dose (E.D.) for population was 35 mu Sv/year. The whole population of Mures county was under study, representing 10.4 million person-year, that is about 615,000 persons followed over a period of 17 years, between 1980-1996. We have calculated the incidence rate of thyroid cancer per 100,000 inhabitants and its distribution per sexes, age groups (nurseling, child, teenager, adult) and per environment (urban-rural). We have also calculated the dynamics indexes (%), which can show the dynamics of this malignant disease over the investigated period and the percentage of thyroid cancer compared to other malignant diseases. Thyroid cancer represents a very small proportion - less than 1 % of the total number of new cancer cases recorded annually in Mures county, with an incidence rate between 0.16-1.81 %000, the maximum value being registered in 1995. We have observed differences in the distribution of the disease in the two sexes, the incidence rate being all the time higher in women than in men. The incidence rate is also higher in the urban environment than in rural one, especially before 1986. By monitoring the thyroid neoplasia morbidity over age we have discovered just one case in young age (in 1995), all the other cases affecting only adults. Even though during the whole investigated period the thyroid cancer incidence presents a constant tendency to increase, more pronounced since 1993, the excess relative risk (observed cases/expected cases) is insignificant correlated with the supplementary average dose of radiation received post-accident by the population.