A common virus that in most people triggers nothing more than German measles or flu could be the answer to the mystery of childhood cancers near the Sellafield nuclear reprocessing site in Cumbria, in the north of England, scientists believe.
Sir Richard Doll, the epidemiologist who first established the link between smoking and lung cancer, has endorsed the theory that an infectious agent rather than radiation is the cause of the Sellafield cluster.
The thesis was produced by Prof Leo Kinlen of Oxford university, who has spent two decades amassing evidence in its support. But a study published in the British Journal of Cancer today is considered by Sir Richard and others to clinch the case.
Prof Kinlen's theory is that "population mixing" has caused the spread of an infection which has triggered leukaemia in susceptible young people. Seascale, the village beside the nuclear plant, has 10 times the number of childhood leukaemias that would be expected for its population. Prof Kinlen believes the epidemic has been caused by a massive influx of different groups of people into a remote and rural area.
He has established the same pattern of infection in a number of areas with an influx of people which have no connection with the nuclear industry. The theory is that workers on the massive Sellafield construction project have brought in the infectious agent, and that it has been passed to the population of scientists, nuclear workers and their families who have lived a more sheltered existence.
"For any infection to take hold you have to have susceptibilities - people who have not met the agent," said Prof Kinlen. The scientific and professional community arrived at Seascale first. "In the 1960s and 1970s, Sellafield was the rural parish with far and away the largest proportion of social class ones. There were excellent 11 plus results."
Into this community which combined isolation with high social class came thousands of construction workers. Sellafield became the largest industrial site in Europe. "The workers were often saving on accommodation allowances by hot-bedding (shift workers sharing beds)," said Prof Kinlen. Many were very mobile, moving in pursuit of work from oil rigs in the Middle East to construction projects all over Europe.
The latest study, by Dr Heather Dickinson and Dr Louise Parker from Newcastle University's department of child health, is based on records that show children in Cumbria are more likely to develop leukaemia if their parents come from outside the county, and that if both their parents were from outside Cumbria.
The scientists established a mathematical model for predicting how many leukaemia cases there should be at Sellafield. From 1950 to 1989, there were six cases of childhood leukaemia in children born in Seascale and two among children who moved there. The model correctly predicted the numbers - although they were at the higher end of what was expected.