Children living immediately downwind of the April 1986 Chernobyl nuclear plant accident have developed autoimmune thyroid abnormalities at almost seven times the rate of those who lived upwind of the reactor's fallout, reports an international team of researchers in the Sept. 5 LANCET.

The thyroid collects radioactive iodine from nuclear fallout. An earlier study found an excess of thyroid cancers among children exposed to Chernobyl fallout (SN: 6/17/95, p. 381). In this study, Furio Pacini of the University of Pisa in Italy and his colleagues assayed for noncancerous thyroid disorders in children who were less than 13 years old at the time of the accident. Nearly 300 came from a village subjected to a heavy rein of fallout. Another 200 had been exposed to almost no radiation.

The group exposed to high levels of Chernobyl fallout had an unusually high incidence of antibodies to thyroid cells, suggesting that their immune systems were attacking the organ, Pacini's group notes. Among these children, the incidence was highest in girls at least 6 years old at the time of the accident. They were more than twice as likely to have the antibodies as were fallout-exposed boys of their age-and almost 10 times as likely as were girls their age from the unexposed town.

Some studies have suggested that high estrogen production increases a person's vulnerability to autoimmune disease. This might partially explain why fallout-exposed girls who, before the study, had undergone puberty faced the highest rate of autoimmune thyroid disease, Pacini says.