In the on-going debate over whether proximity to high voltage power lines may be linked to childhood leukemia, researchers have found the association remains "slight" and "the relation may be due to chance."
Over the years there have been several studies that either support or contradict a relationship between electromagnetic fields and cancer.
This current study compared approximately 29,000 cases of cancer in the UK, and included 9700 cases of leukemia, diagnosed before age 15 years, with a similar number of cancer-free "controls" matched for gender, date of birth, and birth registration district.
Dr. Gerald J. Draper, at the University of Oxford, and his associates who identified subjects living within 1 kilometer of 275 kV and 400 kV overhead power lines, found no association between distance from power lines and overall incidence of cancer.
They say they did however find that children living within 200 meters of a power line had a 69 percent higher risk of leukemia than those who lived more than 600 meters away. Between those two distances, the risk was increased by 23 percent.
But the team add that as this is further than can readily be explained by magnetic fields it may be due to other factors associated with power lines.
Dr. Heather O. Dickinson, from the University of Newcastle upon Tyne, in an accompanying editorial, notes that magnetic fields surrounding power lines amounts to "about 1% of the earth's magnetic field, which affects all of us all the time. So, she suggests, the relationships that Draper's group observed may reflect another factor that varies geographically.
Dr. Geoff Watts, British Medical Journal ( BMJ) science editor, points out that proposed mechanisms supporting a link between electromagnetic fields and cancer "is at best thin and at worst non-existent".
He adds that even if such a link exists, Draper's findings indicate that power lines may be associated with only about five cases of childhood leukemia each year.
The study is published in the British Medical Journal.