July 25, 1996. Copyright, 1996, Graphic News. All rights reserved

CHERNOBYL CLOUD HAS SILVER LINING
By Laura Spinney, Science Editor

LONDON, July 25, Graphic News- An outbreak of leukaemia among children in parts of Greece contaminated by the fallout from Chernobyl has thrown light on possible causes of the disease, say American and Greek doctors today.

The exact causes of childhood leukaemia, which accounts for about one third of cancers diagnosed in children in developed countries, are unknown. A small fraction of cases are thought to be caused by natural background radiation, but because most children are exposed to similar doses that has been hard to prove. Since the nuclear explosion at Chernobyl, Ukraine in 1986, northern Greece has provided doctors with a natural experiment in the relationship between increased background radiation and leukaemia. Based on their analysis of Greek medical records,  Dr Eleni Petridou of the Harvard Center for Cancer Prevention in Boston, Massachusetts and colleagues from America and Greece have confirmed that background radiation is a factor Ð but only when infants are exposed in the womb. They publish their findings in this weekÕs issue of the journal ÔNatureÕ.

Parts of northern Greece were among the most highly contaminated areas outside the former Soviet Union after the Chernobyl disaster. In areas where the background radiation was doubled, PetridouÕs team found a 2.6-fold increase in the number of cases of infant leukaemia Ð one form of childhood leukaemia associated with a very specific genetic abnormality. And children born to women in the most highly contaminated areas Ð where the radiation dose was between five and ten times the normal background level Ð were more likely to develop infant leukaemia.

ÔWe have shown that even a minimal level of ionising radiation can cause cancer, which has been a controversial issue,Õ says Dr Dimitrios Trichopoulos, another of the researchers. PetridouÕs team have also shown that there was no increase in the incidence of the disease among children whose parents were exposed before they were conceived, suggesting that infants are most susceptible to background radiation when they are in the womb. According to Trichopoulos, that finding will have a bearing on the British controversy over the Sellafield nuclear processing plant in Cumbria, where it has been claimed that exposure of male workers to radiation increases the risk that their children will develop leukaemia. 

Sources: Nature, Harvard Center for Cancer Prevention