Contrary to some previous research as well as popular belief, living underneath or near to power lines as a child may not have any notable effect on childhood leukemia risk, according to a new case-control study conducted in the United Kingdom.
“Exposure to power-frequency electric magnetic fields (EMFs) and associated risks of various diseases have been studied for [greater than] 30 years,” wrote researchers led by Kathryn J. Bunch of Oxford University, in the British Journal of Cancer on February 6. Though lab evidence has been largely negative for such associations and “no plausible biological mechanisms” have been described, a somewhat consistent association specifically between magnetic fields and childhood leukemia. Bunch’s group described a positive association between close proximity to power lines in a 2005 paper, and the new research extends that study out to more types of power lines and to farther distances from the lines, as well as with more recent data.
The study included 53,515 children from the National Registry of Childhood Tumours 1962-2008 as well as matched control patients. They assessed the distances of the patient’s mother’s address from power lines of 132, 275, and 400 kV. They found, in general, that the excess risk for leukemia at distances out to 600 meters from power lines has declined over time.
In the 1960s, the relative risk (RR) for leukemia for children living less than 200 meters from the higher voltage lines (275 or 400 kV) compared to those living more than 1000 meters from the lines was 4.50 (95% CI, 0.97-20.83). By the 2000-2008 period, that RR was 0.71 (95% CI, 0.49-1.03). The aggregate RR over the full time period studied was 1.12 (95% CI, 0.90-1.38), and was thus not significant.
The lack of good evidence in other diseases and change over time in leukemia suggests other factors aside from the power lines themselves are likely to blame. “We have observed, in an as yet unpublished analysis, a similar effect of excess leukemia risk (but few other increased tumor risks) declining over time in the vicinity of point sources of potential exposure to ionizing radiation” at other spots in the United Kingdom, the authors wrote. The most convincing explanation in that instance as well lies in details of the population rather than the radiation.
“If the result [of this study] is not due to study artefact or change, the only remaining possibility seems to lie in changing population characteristics of people living near power lines,” they concluded.