Occupational exposures and cancer: a review of agents and relative risk estimates

Our plain-English summary of Occupational exposures and cancer: a review of agents and relative risk estimates, by C. Marant Micallef, K.D. Shield, I. Baldi, et al (Occupational and Environmental Medicine, 2018).

The study

• Authors: C. Marant Micallef, K.D. Shield, I. Baldi, B. Charbotel, B. Fervers, A. Gilg Soit Ilg, P. Guénel, A. Olsson, L. Rushton, S.J. Hutchings, K. Straif, I. Soerjomataram
• Journal: Occupational and Environmental Medicine
• Published: 2018;75(8):604-614
• Cited by: 50 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: The contribution of occupational exposures to the cancer burden can be estimated using population-attributable fractions, which is of great importance for policy making. This paper reviews occupational carcinogens, and presents the most relevant risk relations to cancer in high-income countries using France as an example, to provide a framework for national estimation of cancer burden attributable to occupational exposure.

Methods: Occupational exposures that should be included in cancer burden studies were evaluated using multiple criteria: classified as carcinogenic or probably carcinogenic by the International Agency for Research on Cancer (IARC) Monographs volumes 1-114, being a primary occupational exposure, historical and current presence of the exposure in France and the availability of exposure and risk relation data. Relative risk estimates were obtained from published systematic reviews and from the IARC Monographs.

Results: Of the 118 group 1 and 75 group 2A carcinogens, 37 exposures and 73 exposure-cancer site pairs were relevant. Lung cancer was associated with the most occupational carcinogenic exposures (namely, 18), followed by bladder cancer and non-Hodgkin's lymphoma. Ionising radiation was associated with the highest number of cancer sites (namely, 20), followed by asbestos and working in the rubber manufacturing industry. Asbestos, bis(chloromethyl)ether, nickel and wood dust had the strongest effect on cancer, with relative risks above 5.

Conclusions: A large number of occupational exposures continues to impact the burden of cancer in high-income countries such as France. Information on types of exposures, affected jobs, industries and cancer sites affected is key for prioritising policy and prevention initiatives.

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

In plain English

This was a review, not a new study of workers. Experts listed workplace exposures that the International Agency for Research on Cancer (IARC) classes as carcinogenic or probably carcinogenic. They gathered relative risks from published studies, with France as the example high-income country. They did not conduct a new systematic review, but searched Medline for recent reviews when needed. They kept 37 exposures, including asbestos (all forms), and 73 exposure-cancer site pairs, 44 with sufficient and 29 with limited human evidence. Asbestos had sufficient evidence for four cancer sites. Asbestos relative risks were 1.6 (95% CI 1.4 to 1.9) for lung cancer in Europe, 1.2 (1.01 to 1.4) for larynx cancer, and 1.8 (1.4 to 2.3) for ovarian cancer overall, 2.8 (1.4 to 5.7) at high exposure. No mesothelioma relative risk was given; the authors called that risk very high and well established. The largest listed relative risks, above 5, were for bis(chloromethyl)ether, nickel and wood dust. The authors concluded that many workplace exposures affect cancer risk. They noted the figures do not account for overlapping exposures or interactions such as smoking.

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: Review that selected occupational carcinogens using IARC Monograph classifications and compiled relative risk estimates from an earlier UK systematic review, the IARC Monographs, Medline searches for recent meta-analyses or systematic reviews, and large cohort studies; not a new systematic review
• Who was studied: Agents classified by IARC Monographs volumes 1 to 114 (118 group 1 and 75 group 2A), of which 87 were judged occupational; France was the example high-income country, with a reference exposure period of 1965 to 2015
• Exposure: 37 occupational exposures (chemicals, dusts, jobs and industries, ionising radiation, shiftwork), including asbestos (all forms), present in the workplace at some time from 1965 to 2015
• Main results:
  • Of 94 pairs linked to the 37 exposures, 73 exposure-cancer site pairs were retained: 44 with sufficient evidence and 29 with limited evidence
  • Lung cancer was associated with the most occupational exposures (18), followed by bladder cancer (9) and non-Hodgkin's lymphoma (9)
  • Ionising radiation was linked with sufficient evidence to 20 cancer sites. Asbestos ranked second, with sufficient evidence for four sites (larynx, lung, ovary and mesothelioma in the tables), and the rubber manufacturing industry ranked third, with three sites
  • Asbestos and lung cancer: relative risk 1.6 (95% CI 1.4 to 1.9) for all exposure combined in Europe, adjusted for smoking, taken from Moon 2013
  • Asbestos and larynx cancer: relative risk 1.2 (95% CI 1.01 to 1.4) for any exposure, taken from a 2006 National Academy of Sciences / Institute of Medicine meta-analysis of cohort studies based on mortality
  • Asbestos and ovarian cancer: relative risk 1.8 (95% CI 1.4 to 2.3) for any exposure and 2.8 (95% CI 1.4 to 5.7) for high exposure, taken from the Camargo 2011 meta-analysis based on mortality
  • Asbestos pairs with limited evidence, all taken from the Institute of Medicine 2006 meta-analysis: pharynx 1.4 (95% CI 1.04 to 2.0) for ever exposed; colorectal 1.2 (95% CI 1.0 to 1.3) and stomach 1.2 (95% CI 1.1 to 1.3) for any exposure
  • No relative risk was presented for asbestos and mesothelioma. The authors stated that the increased risk is very high and well established, and that burden studies usually attribute a percentage (sometimes 100%) of registered cases to asbestos
  • Among sufficient-evidence pairs, relative risks above 5 were listed for bis(chloromethyl)ether and lung cancer (7.6, all exposure levels), nickel and nasal cavity cancer (8.7, all levels) and wood dust and nasal cavity cancer (5.8, highest exposure)
• The authors' conclusion: The authors concluded that a large and diverse number of occupational exposures affect cancer risk, and that the listed exposures and relative risks can serve as a basis for cancer burden studies in high-income countries
• Limitations the authors state:
  • The review did not involve a new systematic review of the literature; it relied on existing systematic reviews, the IARC Monographs and experts to identify relevant studies
  • Exposure measurement in monitoring and surveillance studies often differs from that used in the epidemiological studies that supplied the relative risks
  • Many relative risks were not statistically significant, especially for low exposure levels or for women; the authors said this does not necessarily mean there is no association
  • The relative risks assume independence and do not account for overlapping exposures or for interactions with other workplace agents, tobacco smoking or genetic factors

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Relative Risk, Carcinogenic, IARC, Systematic Review, Lung Cancer.

Related studies

• Cancers in France in 2015 attributable to occupational exposures — C. Marant Micallef, K.D. Shield, et al. (2019)
• An estimate of cancers attributable to occupational exposures in France — P. Boffetta, P. Autier, et al. (2010)
• Estimated number of cancers attributable to occupational exposures in France in 2017: an update using a new method for improved estimates — C. Marant Micallef, H. Charvat, et al. (2023)
• Estimates of work-related cancers in workers exposed to carcinogens — F. Deschamps, M. Barouh, et al. (2006)
• Banding carcinogenic risks in developed countries: A procedural basis for qualitative assessment — B.W. Stewart (2008)
• Application of Pattern Mining Methods to Assess Exposures to Multiple Airborne Chemical Agents in Two Large Occupational Exposure Databases from France — J.F. Sauvé, A. Emili, et al. (2022)

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