Occupational exposure to chlorinated solvents and risk of head and neck cancer in men: a population-based case-control study in France

Our plain-English summary of Occupational exposure to chlorinated solvents and risk of head and neck cancer in men: a population-based case-control study in France, by C. Barul, A. Fayossé, M. Carton, et al (Environmental Health, 2017).

The study

• Authors: C. Barul, A. Fayossé, M. Carton, C. Pilorget, A.S. Woronoff, I. Stücker, D. Luce, ICARE study group
• Journal: Environmental Health
• Published: 2017;16(1):77
• Cited by: 32 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Few epidemiological studies have investigated the link between occupational exposure to solvents and head and neck cancer risk, and available findings are sparse and inconsistent. The objective of this study was to examine the association between occupational exposure to chlorinated solvents and head and neck cancer risk.

Methods: We analyzed data from 4637 men (1857 cases and 2780 controls) included in a population-based case-control study, ICARE (France). Occupational exposure to five chlorinated solvents (perchloroethylene [PCE], trichloroethylene [TCE], methylene chloride [MC], chloroform [CF], and carbon tetrachloride [CT]) was assessed through job-exposure matrices. Odds ratios (ORs) and confidence intervals (95% CI) were estimated by unconditional logistic regression, adjusted for age, tobacco smoking, alcohol consumption, asbestos exposure, and other potential confounders.

Results: We observed no association between chlorinated solvent exposure and head and neck cancer risk, despite a non-significant increase in risk among subjects who had the highest cumulative level of exposure to PCE, (OR = 1.81; 95% CI = 0.68 to 4.82). In subsite analysis, the risk of laryngeal cancer increased with cumulative exposure to PCE (p for trend = 0.04). The OR was 3.86 (95% CI = 1.30 to 11.48) for those exposed to the highest levels of PCE. A non-significant elevated risk of hypopharyngeal cancer was also observed in subjects exposed to the highest levels of MC (OR = 2.36; 95% CI = 0.98 to 5.85).

Conclusion: Our findings provide evidence that high exposure to PCE increases the risk of laryngeal cancer, and suggest an association between exposure to MC and hypopharyngeal cancer. Exposure to other chlorinated solvents was not associated with the risk of head and neck cancer.

In plain English

This French case-control study (ICARE, 2001 to 2007) compared 1857 men with squamous cell cancers of the oral cavity, pharynx and larynx with 2780 male controls. Exposure to five chlorinated solvents was estimated from work histories: perchloroethylene (PCE), trichloroethylene (TCE), methylene chloride (MC), chloroform and carbon tetrachloride. Results were adjusted for age, smoking, alcohol, asbestos and other factors. Overall, no solvent showed a statistically significant increase in head and neck cancer risk. Laryngeal cancer risk rose with cumulative PCE exposure (p for trend = 0.04); the highest group's odds ratio was 3.86 (95% CI 1.30 to 11.48). Men with the highest MC exposure had a non-significant raised odds ratio for hypopharyngeal cancer: 2.36 (95% CI 0.98 to 5.85). In men never exposed to asbestos, TCE showed no overall association (odds ratio 1.06, 95% CI 0.66 to 1.70). Among them, the highest TCE group had a non-significant odds ratio of 1.40 (95% CI 0.48 to 4.06; eight cases). The authors concluded that high PCE exposure may increase laryngeal cancer risk. They noted few exposed cases, wide confidence intervals and possible exposure misclassification.

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: Population-based case-control study (the ICARE study), analyzed with unconditional logistic regression
• Who was studied: 4637 men in ten areas of France covered by cancer registries, studied 2001 to 2007. There were 1857 cases with squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, oral cavity or pharynx not otherwise specified, or larynx, and 2780 male controls.
• Exposure: Lifetime occupational exposure to perchloroethylene (PCE), trichloroethylene (TCE), methylene chloride (MC), chloroform (CF) and carbon tetrachloride (CT). Exposure was estimated from job histories with job-exposure matrices and measured as ever/never, duration and a cumulative exposure index. Asbestos exposure was assessed with a separate job-exposure matrix and adjusted for.
• Main results:
  • In the analysis of each solvent separately, there was no significant association between head and neck cancers combined and ever exposure, duration of exposure or cumulative exposure to any of the five solvents.
  • For all head and neck cancers combined, men in the highest cumulative exposure group had non-significantly raised odds ratios compared with never exposed men. The odds ratio was 1.81 (95% CI 0.68 to 4.82) for PCE and 1.42 (95% CI 0.70 to 2.87) for MC.
  • For laryngeal cancer, risk increased with cumulative PCE exposure (p for trend = 0.04). Men with the highest PCE exposure had an odds ratio of 3.86 (95% CI 1.30 to 11.48).
  • The raised laryngeal cancer risk in the highest PCE group remained significant after adjustment for occupational class, with an odds ratio of 3.09 (95% CI 1.05 to 9.13).
  • For hypopharyngeal cancer, men with the highest MC exposure had an elevated but not statistically significant odds ratio of 2.36 (95% CI 0.98 to 5.85). The trend was not significant (p = 0.22).
  • The odds ratio for hypopharyngeal cancer in the highest MC group fell after further adjustment. It was 2.08 (95% CI 0.86 to 5.04) when adjusted for occupational class and 1.57 (95% CI 0.60 to 4.12) when adjusted for level of education.
  • The authors repeated the analysis among men never exposed to asbestos (479 cases and 1159 controls). In this group there was no association between TCE exposure and head and neck cancer: the odds ratio was 1.06 (95% CI 0.66 to 1.70), based on 55 exposed cases.
  • Among men never exposed to asbestos, those with the highest cumulative TCE exposure had a non-significantly raised odds ratio of 1.40 (95% CI 0.48 to 4.06), based on eight exposed cases.
  • The authors tested whether each solvent's effect differed with smoking, alcohol drinking or asbestos exposure. None of these interactions was statistically significant.
• The authors' conclusion: The authors concluded that high occupational exposure to PCE may increase the risk of laryngeal cancer. They added that this suggests a likely carcinogenic effect of PCE on parts of the respiratory tract other than the lung.
• Limitations the authors state:
  • Exposure was assessed retrospectively with job-exposure matrices. This produces misclassification that is likely to be the same for cases and controls, which could bias results toward finding no effect.
  • The number of exposed cases was small for some solvents, which produced wide confidence intervals.
  • The authors could not study the effect of exposure to PCE alone, without other solvents.
  • Most men exposed to TCE were also exposed to asbestos, so including asbestos in the models may have led to overadjustment.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Case-Control Study, Odds Ratio, confidence interval, Asbestos Exposure, Laryngeal Cancer, Cumulative Exposure.

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• Occupational dust exposure and head and neck squamous cell carcinoma risk in a population-based case-control study conducted in the greater Boston area — S.M. Langevin, M.D. McClean, et al. (2013)
• Investigation of occupational and environmental causes of respiratory cancers (ICARE): a multicenter, population-based case-control study in France — D. Luce, I. Stücker, et al. (2011)
• Exposure to chlorinated solvents and lung cancer: results of the ICARE study — F. Mattei, F. Guida, et al. (2014)
• Multidimensional analysis of the effect of occupational exposure to organic solvents on lung cancer risk: the ICARE study — F. Mattei, S. Liverani, et al. (2016)
• Systematic screening for occupations and occupational exposures in head and neck squamous cell carcinoma patients — S. Deneuve, B. Charbotel, et al. (2019)

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