Childhood leukaemia risk: magnetic fields versus distance from power lines

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This was a meta-analysis investigating the possible relationship between childhood leukaemia and living near power lines. The study included 4879 cases and 4835 controls. Exposure to power lines was assessed by assessing magnetic field strength and residential distance to power lines. Homes that were determined to be close enough to power lines and of sufficient voltage to have elevated magnetic fields had measurements taken. Additionally, all residences close to power lines over 100 kV had their exposure modelled and calculated. All other residences were considered to be exposed to a magnetic field of less than 0.1 µT. The study found that there was no statistically significant increased risk of childhood leukaemia associated with living within 50 meters of a power line (odds ratio (OR) of 1.44 with a 95% confidence interval (CI) of 0.63 - 3.29) or being exposed to a magnetic field above 0.4 µT (OR of 1.24 with a 95% CI of 0.50 – 3.05). However, when the authors examined participants who lived within 50 meters of 200 kV power lines and had a magnetic field above 0.4 µT, there was an increased risk of childhood leukaemia (OR of 4.06 with a 95% CI of 1.16 – 14.3). The authors concluded that their results suggest magnetic field exposure is not causally related to childhood leukaemia. They further suggest that there could be an unidentified explanation for the possible link between power lines and childhood leukaemia. 
 

Childhood leukemia risk in the California Power Line Study: Magnetic fields versus distance from power lines

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A similar study by Draper et al 2005 also found an association between distance to power lines and a small increased risk of childhood leukaemia. However, Draper et al did not calculate or measure the magnetic field exposure of the included participants. When the Crespi et al study examined exposure to magnetic fields, it was found that elevated exposure alone was not associated with childhood leukaemia. Both authors conclude that their results did not casually link magnetic field exposure to childhood leukaemia. 

The major positive result in the Crespi et al study was limited by a small sample size, as there was only 13 cases and 3 controls who lived within 50 meters from a power line and were exposed to magnetic fields greater than 0.4 µT. The epidemiological and laboratory evidence for an association between childhood leukaemia and magnetic field exposure has been reported as weak and it is not known how magnetic field exposure could cause childhood leukaemia (WHO, 2007).