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Chernobyl Update

Age and Species Susceptibility to Toxicity from Environmental Radioactivity Due to the Chernobyl Disaster

Cham E. Dallas, Ph.D., Director of Toxicology, University of Georgia, Athens, Georgia

The Chernobyl nuclear disaster in the former Soviet Union, which involved the release of over 100 times the amount of radiation in the Hiroshima and Nagasaki atomic bomb detonations has provided the closest approximation yet of a widespread post-nuclear war environment contaminated by the aerial dispersion of fallout. Research on the deposition of radionuclides and certain parameters of toxicity related to the accident have revealed interesting new relationships concerning the influence of age and species specificity on the toxic responses seen due to environmental radioactivity. The influence of age on the radiation dose received is presented in Chernobyl-contaminated areas in Russia, together with the resulting incidence and character of radiation-induced thyroid cancer. A surprising finding relative to the geographic incidence of these radiation effects is discussed, in which spatial distribution of radiocesium and radioiodine in soil, population, and geographic parameters of transportation arteries are correlated. An interesting finding is the lack of a consistent correlation between the spatial distribution of radionuclides in the soil and thyroid cancer incidence. Instead, most of the thyroid cancer cases were diagnosed in settlements situated on major railways and roads. Also presented is the incidence of congenital malformations in Chernobyl-contaminated versus in contaminated areas, and the relationship of this reproductive incidence with dramatic birth rate anomalies. The distribution of radionuclides in living systems is compared between species for cohorts of highly contaminated individuals. Extraordinarily high disposition of radionuclides in rodents from areas around the Chernobyl reactor are compared to the disposition in aquatic species, soil and sediment distribution and to Chernobyl liquidators (Soviet workers who were involved in cleanup after the accident). The species differences in toxicity response are also evaluated, including differences in radiation-induced oxidative stress responses, cell cycle distribution and changes in DNA content of red blood cells, leukocytes, and whole blood and aneuploidy. The relevance of these findings to economic and sociological parameters is also addressed, such as in family planning and remediation strategies. The utility of this data for more accurately predicting the probable consequences of the use of nuclear weapons are discussed, with a focus on some of the unexpected lessons that have been learned from the Chernobyl disaster.

Nuclear power plants around the world

SOURCE: IAEA, 1996a.