Ionising radiation has long been recognised as a cause of leukaemia in exposed children. But delegates at a conference in London yesterday heard how ground-breaking research is now providing evidence that the children of men exposed to radiation may also be at increased risk of developing leukaemia.
The causes of leukaemia in children are, in general, poorly understood. The disease is known to be multi-causal, and it is widely accepted that it is multi-stage, initiated in utero with some second event triggering development of the disease in childhood.
The incidence of childhood leukaemia in Britain increased dramatically during the twentieth century. The increase has mainly affected the under-five age group, in whom the risk increased by more than 50 per cent during the second half of the century alone. The reasons for the increase remain unclear and it is only by finding out more about the causes that we can establish whether it is possible to take preventive measures and halt the rising incidence. This is the motivation behind the conference – Childhood leukaemia: incidence, causal mechanisms and prevention – which is being hosted by CHILDREN with LEUKAEMIA, Britain’s leading charity devoted to the conquest of the disease.
The link between ionising radiation and childhood leukaemia is well-established. Increased rates of childhood leukaemia were found in those exposed at a young age to the atomic bombs in Japan. And those receiving radiation in utero from maternal X-rays have also been shown to be at higher risk of developing leukaemia. But it has only recently been recognised that ionising radiation not only increases mutation rates in the exposed somatic cells but also results in an elevated mutation rate many cell divisions after the initial irradiation damage.
Yuri Dubrova, Professor of Genetics at the University of Leicester, obtained the first experimental evidence that germ-line mutation rates in unexposed offspring of irradiated male mice do not return to the mutation rates seen in unexposed individuals but are maintained at levels similar to those of directly exposed males. He then went on to show that the elevated mutation rates persisted into the second generation of offspring, through both the male and female germ-lines.