Occupational exposure of UK adults to ELF magnetic fields.

BACKGROUND: More recently, epidemiological studies have tended to categorise occupational exposure to extremely low frequency (ELF) magnetic fields (MF) on the basis of a job-exposure matrix (JEM), based solely on job title. However, occupational exposure in the UK general population is poorly documented. AIMS: To assess occupational exposure to ELF MF in the UK and evaluate the use of a rigid JEM to assign exposures to subjects in the UK Adult Brain Tumour Study (UKABTS). METHODS: Personal ELF MF measurements were preformed using Emdex II magnetic field meters. Exposure was classified by Standard Occupational Classification (2000), Standard Industrial Classification (1997), and a combined occupation-industry classification. LME models determined the contribution of occupational exposure to the 24 hr cumulative exposure and the contribution of occupation and industry to total variance. RESULTS: 236 individuals provided occupational data covering 117 different occupations. Average exposure was significantly higher at work than at home. Elevated average occupational exposure was found for welding trades, printers, telephonists and filing and other records assistants. The discrimination of a rigid JEM based on occupation is improved by linking the classification with industry and by use of contextual information. CONCLUSIONS: This report constitutes a substantial expansion of information on adult exposure to ELF MF in the UK. There is evidence that the accuracy of exposure assessments based solely on job codes is improved by linking with either industry code or contextual knowledge of equipment, such as electron beam welders, and of power lines or substations in the work environment.