Living within 200 m or between 200–600 m of power lines increases the incidence of childhood leukaemia by 70% or 23%, respectively, according to a study by John Swanson and colleagues (Draper, G. et al. BMJ 330, 1290 (2005)). However, this headline-grabbing result needs to be interpreted with caution.

Electromagnetic fields, such as those produced by power lines, have, among other things, been proposed to influence some biological processes, affect free radicals and even deflect cosmic rays onto people in their vicinity. But evidence to support any of these theories is “at best thin and at worst non-existent,” according to a commentary in the BMJ (Watts, G. BMJ 330 (2005)). So despite Gerald Draper from the study team referring to these findings as “statistically really strong” (http://www.washingtonpost.com/, 2 June 2005), whether actual proximity to power lines is the cause of this pattern of leukaemia incidence is debatable.

The authors accept that the epidemiological results could be due to unidentified factors. Indeed, as electromagnetic fields should not influence people living over 200 m away from the source, other aetiological factors might be responsible for the results. Moreover, according to the study, only 5 of the 400–420 childhood leukaemia cases reported annually could be associated with power lines.

David Grant of Leukaemia Research concludes “There is no reason why anyone should be advised to move house on the basis of these results” (http://www.bbc.co.uk, 3 June 2005.)