Leukaemia, brain tumours and exposure to extremely low frequency magnetic fields:: cohort study of Swiss railway employees

Aims: To investigate the relationship between extremely low frequency magnetic field (ELF-MF) exposure and mortality from leukaemia and brain tumour in a cohort of Swiss railway workers. Methods: 20 141 Swiss railway employees with 464 129 person-years of follow-up between 1972 and 2002 were studied. Mortality rates for leukaemia and brain tumour of highly exposed train drivers (21 mu T average annual exposure) were compared with medium and low exposed occupational groups (i.e. station masters with an average exposure of 1 mu T). In addition, individual cumulative exposure was calculated from on-site measurements and modelling of past exposures. Results: The hazard ratio (HR) for leukaemia mortality of train drivers was 1.43 ( 95% CI 0.74 to 2.77) compared with station masters. For myeloid leukaemia the HR of train drivers was 4.74 (95% CI 1.04 to 21.60) and for Hodgkin's disease 3.29 (95% CI 0.69 to 15.63). Lymphoid leukaemia, non-Hodgkin's disease and brain tumour mortality were not associated with magnetic field exposure. Concordant results were obtained from analyses based on individual cumulative exposure. Conclusions: Some evidence of an exposure-response association was found for myeloid leukaemia and Hodgkin's disease, but not for other haematopoietic and lymphatic malignancies and brain tumours.