Objectives In absence of clear evidence regarding possible effects of occupational chemical exposures on brain tumour aetiology, it is worthwhile to explore the hypothesis that such exposures might act on brain tumour risk in interaction with occupational exposure to extremely low frequency magnetic fields (ELF).
Methods INTEROCC is a seven-country (Australia, Canada, France, Germany, Israel, New Zealand and UK), population-based, case–control study, based on the larger INTERPHONE study. Incident cases of primary glioma and meningioma were ascertained from 2000 to 2004. Job titles were coded into standard international occupational classifications and estimates of ELF and chemical exposures were assigned based on job-exposure matrices. Dichotomous indicators of cumulative ELF (≥50th vs <50th percentile, 1–4 year exposure time window) and chemical exposures (ever vs never, 5-year lag) were created. Interaction was assessed on both the additive and multiplicative scales.
Results A total of 1939 glioma cases, 1822 meningioma cases and 5404 controls were included in the analysis, using conditional logistic regression. There was no clear evidence for interactions between ELF and any of the chemical exposures assessed for either glioma or meningioma risk. For glioma, subjects in the low ELF/metal exposed group had a lower risk than would be predicted from marginal effects. Results were similar according to different exposure time windows, to cut-points of exposure or in exposed-only analyses.
Conclusions There was no clear evidence for interactions between occupational ELF and chemical exposures in relation to glioma or meningioma risk observed. Further research with more refined estimates of occupational exposures is recommended.
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Contributors Study conception and design: MCT and EC. Acquisition of data: GB, SF, MH, DK, DM, MEP, LR, SS, KS, BS, JoS and JaS. Exposure assessment: JDB, JF, LK and MVT. Statistical analysis: MCT. Drafting of manuscript: MCT. All authors participated in the interpretation of data and revision and approval of the manuscript.
Funding MCT was funded by a Government of Canada Banting Post doctoral Fellowship. The INTEROCC study was funded by the National Institutes for Health (NIH) Grant No 1R01CA124759 (PI E Cardis). Coding of the French occupational data was in part funded by AFSSET (Convention No ST-2005-004). The INTERPHONE study was supported by funding from the European Fifth Framework Program, ‘Quality of Life and Management of Living Resources’ (contract 100 QLK4-CT-1999901563) and the International Union against Cancer (UICC). The UICC received funds for this purpose from the Mobile Manufacturers’Forum and GSM Association. In Australia,funding was received from the Australian National Health and Medical ResearchCouncil (EME Grant 219129) with funds originally derived from mobile phone service license fees; a University of Sydney Medical Foundation Program; the Cancer Council NSW and The Cancer Council Victoria. In Canada funding was received from the Canadian Institutes of Health Research (project MOP-42525); the Canada Research Chair programme; the Guzzo-CRS Chair in Environment and Cancer; the Fonds de larecherche en santé du Québec; the Canadian Institutes of Health Research(CIHR), the latter including partial support from the Canadian Wireless Telecommunications Association; the NSERC Chair in Risk Science at the University of Ottawa. In France, funding was received by l’Association pour la Recherche sur le Cancer (ARC) (ContratN85142) and three network operators (Orange, SFR, Bouygues Telecom). In Germany, funding was received from the German Mobile Phone Research Program (Deutsches Mobilfunkforschungsprogramm) of the German Federal Ministry for the Environment, Nuclear Safety, and Nature Protection; the Ministry for the Environment and Traffic of the state of Baden-Wurttemberg; the Ministry for the Environment of the state of North Rhine-Westphalia;the MAIFOR Program (Mainzer Forschungsforderungsprogramm) of the University of Mainz. In New Zealand, funding was provided by the Health Research Council, Hawkes Bay Medical Research Foundation, the Wellington Medical Research Foundation, the Waikato Medical Research Foundation and the Cancer Society of New Zealand. Additional funding for the UK study was received from the Mobile Telecommunications, Health andResearch (MTHR) programme, funding from the Health and Safety Executive, the Department of Health, the UK Network Operators (O2, Orange, T-Mobile, Vodafone, ‘3’) and the Scottish Executive. All industry funding was governed by contracts guaranteeing the complete scientific independence of the investigators.
Competing interests MCT reports personal fees from ICF Incorporated, outside this work. DK reports to serving as Chief Risk Scientist and CEO at Risk Sciences International(http://www.risksciences), a Canadian company established in 2006 in partnership with the University of Ottawa conducting work in risk assessment, management and communication of health and environmental risks and their broader impacts on both public and private interests. He also holds an Industrial Research Chair in Risk Science under a peer-reviewed university–industry partnership programme administered by the Natural Sciences and Engineering Research Council of Canada.
Patient consent Obtained.
Ethics approval Ethics approval was obtained from local research ethics boards, as well as from the Ethical Review Board of IARC (Lyon) for INTERPHONE and the Municipal Institute for Medical Investigation (IMIM) Barcelona for INTERPHONE and INTEROCC.
Provenance and peer review Not commissioned; externally peer reviewed.
Correction notice This paper has been amended since it was published Online First. Owing to a scripting error, some of the publisher names in the references were replaced with ’BMJ Publishing Group'. This only affected the full text version, not the PDF. We have since corrected these errors and the correct publishers have been inserted into the references.