Occupational exposure to low frequency magnetic fields and the risk of low grade and high grade glioma

The purpose of this population-based case control study was to investigate a possible association between occupational exposure to low frequency magnetic fields and the risk of low grade glioma (LGG) and high grade glioma (HGG). The study population consisted of 414 histologically confirmed cases of glioma (LGG = 110, HGG = 304), first diagnosed between July 1987 and December 1991, and 421 controls from Melbourne, Australia, matched by age, sex and postcode of residence. A detailed occupational history was obtained for each subject. Exposure to low frequency magnetic fields was estimated using three different methods: self-report, expert hygienist review and a job exposure matrix (JEM). Elevated but statistically non-significant risk estimates were found for all glioma and HGG when exposure was assessed by the expert hygienist. The odds ratios (OR) for the highest exposed group of workers when assessed by the expert hygienist were 1.4 (95% confidence interval, CI: 0.85-2.27) and 1.51 (95% CI: 0.90-2.53) for all glioma and HGG, respectively. There were inverse associations for the self-reported and JEM exposures for both LGG and HGG but these may reflect limitations in these exposure assessment methods. Our results do not support a role for occupational exposure to low frequency magnetic fields in the development of either LGG or HGG.