After a six year study, the US National Institute of Environmental Health Sciences that there is no evidence linking human disease to the fields generated by power line – but with one exception. They concluded that there was a small statistical association between childhood leukaemia and magnetic fields. Chronic lymphocytic leukaemia in adults also showed a weak link.

However a separate study by scientists from the University of Toronto and Toronto Hospital for Sick Children suggested a stronger link. It found evidence that children exposed to strong magnetic fields were 4.5 times more likely to contract the disease than those not exposed to such fields.

Though the evidence suggests there may be some sort of causal link, scientists have so far been unable to find a satisfactory biological mechanism to account for the results.