INTEROCC case-control study: lack of association between glioma tumors and occupational exposure to selected combustion products, dusts and other chemical agents

Our plain-English summary of INTEROCC case-control study: lack of association between glioma tumors and occupational exposure to selected combustion products, dusts and other chemical agents, by A. Lacourt, E. Cardis, J. Pintos, et al (BMC Public Health, 2013).

The study

• Authors: A. Lacourt, E. Cardis, J. Pintos, L. Richardson, L. Kincl, G. Benke, S. Fleming, M. Hours, D. Krewski, D. McLean, M.E. Parent, S. Sadetzki, K. Schlaefer, B. Schlehofer, J. Lavoue, M. van Tongeren, J. Siemiatycki
• Journal: BMC Public Health
• Published: 2013;13:340
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The aim was to investigate possible associations between glioma (an aggressive type of brain cancer) and occupational exposure to selected agents: combustion products (diesel and gasoline exhaust emissions, benzo(a)pyrene), dusts (animal dust, asbestos, crystalline silica, wood dust) and some other chemical agents (formaldehyde, oil mist, sulphur dioxide).

Methods: The INTEROCC study included cases diagnosed with glioma during 2000-2004 in sub-regions of seven countries. Population controls, selected from various sampling frames in different centers, were frequency or individually matched to cases by sex, age and center. Face-to-face interviews with the subject or a proxy respondent were conducted by trained interviewers. Detailed information was collected on socio-economic and lifestyle characteristics, medical history and work history. Occupational exposure to the 10 selected agents was assessed by a job exposure matrix (JEM) which provides estimates of the probability and level of exposure for different occupations. Using a 25% probability of exposure in a given occupation in the JEM as the threshold for considering a worker exposed, the lifetime prevalence of exposure varied from about 1% to about 15% for the different agents. Associations between glioma and each of the 10 agents were estimated by conditional logistic regression, and using three separate exposure indices: i) ever vs. never; ii) lifetime cumulative exposure; iii) total duration of exposure.

Results: The study sample consisted of 1,800 glioma cases and 5,160 controls. Most odds ratio estimates were close to the null value. None of the ten agents displayed a significantly increased odds ratio nor any indication of dose-response relationships with cumulative exposure or with duration of exposure.

Conclusion: Thus, there was no evidence that these exposures influence risk of glioma.

In plain English

This international case-control study, INTEROCC, examined whether glioma, a brain cancer, was associated with workplace exposure to ten agents, including asbestos. The article did not name an asbestos fiber type. It included 1,800 people diagnosed with glioma between 2000 and 2004 and 5,160 population controls from Australia, Canada, France, Germany, Israel, New Zealand and the UK. Exposure was not self-reported but estimated from job histories using a job exposure matrix adapted from a Finnish one. The matrix classed 16.2% of cases and 12.0% of controls as ever exposed to asbestos. The odds ratio for glioma in those ever versus never exposed to asbestos was 0.9 (95% CI 0.8-1.1), and the odds did not rise with higher cumulative exposure or longer duration. Two borderline results, for sulphur dioxide and long-duration diesel exhaust, were judged most likely due to multiple testing and chance. The authors concluded that their findings do not support an association between any of the agents and glioma. They cautioned that, given limited statistical power, the results are not strong evidence that there is no risk.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: International population-based case-control study (INTEROCC, part of the INTERPHONE study), with controls matched to cases by sex, age and center; analysed by conditional logistic regression
• Who was studied: 1,800 glioma cases diagnosed 2000–2004 and 5,160 population controls, mostly aged 30–59 (up to 69 in some centers), from sub-regions of Australia, Canada, France, Germany, Israel, New Zealand and the UK
• Exposure: Occupational exposure to 10 agents: diesel and gasoline exhaust, benzo(a)pyrene, asbestos (fiber type not specified), crystalline silica, wood dust, animal dust, formaldehyde, oil mist and sulphur dioxide. Exposure was estimated from job histories with a modified Finnish job exposure matrix (FINJEM). 'Ever exposed' meant at least one job with at least 25% probability of exposure, held for at least one year, with a 5-year lag. The reference group in all analyses was people never exposed to the agent.
• Main results:
  • Asbestos was the most prevalent of the dusts: about 16% lifetime prevalence of exposure
  • Asbestos, ever exposed compared with never exposed: 292 cases (16.2%) and 621 controls (12.0%) ever exposed; odds ratio 0.9 (95% CI 0.8-1.1)
  • Asbestos, highest tertile of cumulative exposure compared with never exposed: odds ratio 1.0 (95% CI 0.7-1.3)
  • Asbestos, 10 or more years of exposure compared with never exposed: odds ratio 1.0 (95% CI 0.8-1.3)
  • None of the dusts, including asbestos, showed any association with glioma, either for ever exposure or with increasing cumulative exposure or duration
  • Sulphur dioxide, the least prevalent agent: odds ratio for ever exposure 2.0 (95% CI 1.0-3.8), with the excess concentrated in the lowest categories of cumulative exposure and duration
  • Diesel exhaust, top duration category (10 or more years): borderline significant odds ratio 1.3 (95% CI 1.0-1.8), with no clear dose-response pattern
  • The authors attributed the few borderline results to multiple testing and chance
• The authors' conclusion: The authors concluded that their findings do not support an association between any of the agents examined, including asbestos, and risk of glioma
• Limitations the authors state:
  • Statistical power was limited by low exposure prevalence for some agents, measurement error and low exposure levels, so the null results are not strong evidence that there is no risk
  • Participation rates were 68% for cases and 50% for controls, which raises possible participation bias; the authors judged this unlikely to change their inferences
  • The job exposure matrix gives everyone in the same occupation and era the same exposure estimate, ignoring individual differences in tasks and job environments
  • Exposure estimates were developed in Finland and may not apply equally well to workers in other countries
  • Each agent was analysed separately, ignoring possible confounding by the other agents

Topics

Medical terms in this study, explained in our Lexicon: Case-Control Study, Occupational Exposure, Crystalline, Work History, Cumulative Exposure, Odds Ratio, Dose-response relationship.

Related studies

• The INTEROCC case-control study: risk of meningioma and occupational exposure to selected combustion products, dusts and other chemical agents — D.M. McElvenny, M. van Tongeren, et al. (2018)
• Role of Klotho Protein in Tumor Genesis, Cancer Progression, and Prognosis in Patients with High-Grade Glioma — N. Peshes-Yeloz, L. Ungar, et al. (2019)
• A case-control study of the relationship between the risk of colon cancer in men and exposures to occupational agents — M.S. Goldberg, M.E. Parent, et al. (2001)
• The investigation of brain tumor occurrence in other occupational groups: introduction — I.J. Selikoff (1982)
• Multicentre, population-based, case-control study of particulates, combustion products and amyotrophic lateral sclerosis risk — A.E. Visser, F. D'Ovidio, et al. (2019)
• Occupational risk factors for brain cancer in Canada — S.Y. Pan, A.M. Ugnat, et al. (2005)

Browse more research in BMC Public Health, or return to medical research.