The British Medical Journal last week reported on what appears to be a link between childhood cancer and high voltage power lines. The authors of the study emphasized that the results may be due to chance and further research is needed to find out whether there really is a link.
One child in 2000 develops leukemia before the age of 15 years but the causes are not understood. In recent years researchers have studied a variety of possible explanations including genetic susceptibility, ionizing radiation, unusual patterns of exposure to infection and electromagnetic fields. Since 1979 there has been concern that the fields associated with electric power systems may be associated with cancer. In 2001, the International Agency for Research on Cancer classified extremely low frequency magnetic fields as "possibly carcinogenic" while others, such as the UK Childhood Cancer Study, dispute the risk.
In the latest research, over 29,000 children with cancer, including 9,700 with leukemia, were included in the study. The children, aged 0-14 years, were compared with a group of control children matched for sex, approximate date of birth and birth registration district. The distance of each child's home address at birth from the nearest high voltage power line was calculated. Children who lived within 200m of high voltage power lines at birth appeared to have a 70 percent raised risk of leukemia compared with those who lived beyond 600m. There was also a slightly increased risk for those living 200-600m from the lines at birth. No excess risk was found for other childhood cancers.
The finding that the increased leukemia risk extends so far from the line is surprising in view of the low average level of exposure to magnetic fields at these distances, say the authors. There is no accepted biological mechanism to explain these results; indeed, the relation may be due to chance or some other factor associated with living near power lines. "Magnetic fields from power lines are very weak - only about 1 percent of the earth's magnetic field which affects all of us all the time - so it would be surprising if they caused leukemia. The increased risk closer to power lines may reflect some other factor that varies geographically," explained researcher Heather Dickinson, from the University of Newcastle upon Tyne. "We don't yet fully understand childhood leukemia. Further insights into the causes of childhood leukemia will almost certainly come through advancing technology helping us understand the molecular events which drive leukemia changes," she concluded.
