Occupational Exposure to Extremely Low-Frequency Magnetic Fields and Brain Tumor Risks in the INTEROCC Study

Abstract

Background Occupational exposure to extremely low frequency magnetic fields (ELF) is a suspected risk factor for brain tumours, however the literature is inconsistent. Few studies have assessed whether ELF in different time windows of exposure may be associated with specific histologic types of brain tumours. This study examines the association between ELF and brain tumours in the large-scale INTEROCC study. Methods Cases of adult primary glioma and meningioma were recruited in seven countries (Australia, Canada, France, Germany, Israel, New Zealand, United Kingdom) between 2000 and 2004. Estimates of mean workday ELF exposure based on a job exposure matrix assigned. Estimates of cumulative exposure, average exposure, maximum exposure, and exposure duration were calculated for the lifetime, and 1–4, 5–9, and 10+ years prior to the diagnosis/reference date. Results There were 3,761 included brain tumour cases (1,939 glioma, 1,822 meningioma) and 5,404 population controls. There was no association between lifetime cumulative ELF exposure and glioma or meningioma risk. However, there were positive associations between cumulative ELF 1–4 years prior to the diagnosis/reference date and glioma (odds ratio (OR) ≥ 90th percentile vs < 25th percentile = 1.67, 95% confidence interval (CI) 1.36–2.07, p < 0.0001 linear trend), and, somewhat weaker associations with meningioma (OR ≥ 90th percentile vs < 25th percentile = 1.23, 95% CI 0.97–1.57, p = 0.02 linear trend). Conclusions Results showed positive associations between ELF in the recent past and glioma. Impact Occupational ELF exposure may play a role in the later stages (promotion and progression) of brain tumourigenesis.

Interactions between occupational exposure to extremely low frequency magnetic fields and chemicals for brain tumour risk in the INTEROCC study

“…Finally, participation rates were low, ranging from 68% to 81% in cases to 50% in controls. Though participation may be related with socioeconomic and employment status,46 level of educational attainment and occupational prestige (based on the standard international occupational prestige scale) were generally similar across groups of interviewed participants here 28. The somewhat lower participation rate for glioma as compared with meningioma cases was expected due to the severity of disease and poorer prognosis.…”

“…In the international INTEROCC study, a large-scale, population-based, case–control study including data on nearly 2000 cases of both glioma and meningioma, based on the larger INTERPHONE study, we recently reported no association between lifetime cumulative ELF exposure and glioma or meningioma risk, although positive associations with ELF were noted in the most recent ETW, 1–4 years prior to the diagnosis/reference date (OR≥90th percentile vs <25th percentile for glioma=1.67, 95% CI 1.36 to 2.07; for meningioma=1.23, 95% CI 0.97 to 1.57) possibly suggesting an aetiological role of ELF in brain tumour promotion or progression 28. Although there was no clear evidence for associations between occupational exposure to combustion products, dusts and other chemical agents29 or solvents30 and either glioma or meningioma risk in INTEROCC, we recently observed evidence for positive associations between occupational metal exposures, particularly iron exposure in women, as well as oil mist exposure overall, and meningioma risk (Ref.…”

“…The main analysis of the current study was based on dichotomised categories of ELF exposure in the 1–4 year ETW (according to the 50th percentile), since ELF is suspected of playing a role in brain tumour promotion or progression and chemical exposures with a 5-year lag (never versus any exposure) 28. However, we also considered alternate ETWs for both ELF (1-year lag, 5–9 year ETW and 10-year lag) and chemical exposures (1-year lag, 1–9 year ETW) in sensitivity analyses.…”

“…Models were stratified by country-region, sex and 5 year age groups and were adjusted for level of education. The main analysis focused on interactions between cumulative occupational ELF in the 1–4 year ETW, since we were interested in assessing potential promotion or progression effects of ELF, and the strongest independent effects of ELF were observed with this metric in this time window in previous work 28. Occupational chemical exposures were considered with a 5-year lag, also as in previous work 29–31.…”

The INTEROCC case-control study: risk of meningioma and occupational exposure to selected combustion products, dusts and other chemical agents

“…Additional analyses found inconsistent evidence for an association between the use of synthetic hair dye and meningioma6 and an association between meningioma and herbicide or insecticide exposure among women, but not in men 7. A French population-based case-control study concluded that meningioma may be caused by occupational or residential exposure to electromagnetic fields,8 although the evidence in support of an association with occupational exposure from the INTEROCC international study was somewhat weaker 9. No association was found between mobile phone use and meningioma 10 11.…”