Leukaemia mortality in relation to magnetic field exposure: findings from a study of United Kingdom electricity generation and transmission workers, 1973-97

Objective-To investigate whether risks of leukaemia are related to occupati onal exposure to magnetic fields. Methods-The mortality experienced by a cohort of 83 997 employees of the fo rmer Central Electricity Generating Board of England and Wales was investig ated for the period 1973-97. Ah employees were employed for at least 6 mont hs with some employment in the period 1973-82. Computerised work histories were available for 79 972 study subjects for the period 1971-93. Detailed c alculations were performed by others to enable a novel assessment to be mad e of exposures to magnetic fields. Two analytical approaches were used, ind irect standardisation (n=83 997) and Poisson regression (n=79 972). Results-Based on serial mortalities for England and Wales, the standardised mortality ratio of 84 for all leukaemias (observed ill, expected 132.3) wa s similar to that of 83 for all causes (observed 14 845, expected 17 918). No significant positive trends were found for the risks of various types of leukaemia (chronic lymphatic leukaemia, acute myeloid leukaemia, chronic m yeloid leukaemia, all leukaemia) either with lifetime cumulative exposure t o magnetic fields or with such exposures received in the most recent 5 year s. Conclusions There are no discernible excess risks of leukaemia as a consequ ence of occupational exposure to magnetic fields in United Kingdom electric ity generation and transmission workers.