Occupational exposure to rock wool and glass wool and risk of cancers of the lung and the head and neck: a systematic review and meta-analysis

Our plain-English summary of Occupational exposure to rock wool and glass wool and risk of cancers of the lung and the head and neck: a systematic review and meta-analysis, by L. Lipworth, C. La Vecchia, C. Bosetti, et al (Journal of Occupational and Environmental Medicine, 2009).

The study

• Authors: L. Lipworth, C. La Vecchia, C. Bosetti, J.K. McLaughlin
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2009;51(9):1075-87
• Type of article: Meta-analysis, Systematic review
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To conduct a review and meta-analysis of risks of cancers of the lung and head and neck (HN) from exposure to rock wool (RW) and glass wool (GW).

Methods: We performed a systematic review and meta-analysis of risk estimates of lung and HN cancer in epidemiologic studies of workers exposed to man-made vitreous fibers (MMVF), specifically RW and GW.

Results: Sixteen estimates of lung cancer risk yielded a summary relative risk (RR) of 1.21 (95% CI = 1.11 to 1.32, based on 1662 exposed cases). Corresponding RRs were 1.26 (95% CI = 1.10 to 1.44) in studies of production workers (with similar risk for RW and GW workers), 1.06 (95% CI = 0.77 to 1.48) in studies of end users, and 1.18 (95% CI = 0.98 to 1.42) in community-based studies. The summary RR for HN cancer was 1.36 (95% CI = 1.13 to 1.63, 414 exposed cases). With a few exceptions, all studies that assessed the risk of lung or HN cancer according to various indices of MMVF exposure failed to detect a dose-risk relation. There was limited evidence of a confounding effect of tobacco smoking. No clear excess of pleural mesothelioma has been reported in MMVF-exposed workers.

Conclusions: Despite a small elevation in RR for lung cancer among MMVF production workers, the lack of excess risk among end users, the absence of any dose-risk relation, the likelihood of detection bias, and the potential for residual confounding by smoking and asbestos exposure argue against a carcinogenic effect of MMVF, RW, or GW at this time. Similar conclusions apply to HN cancer risk among workers exposed to MMVF.

In plain English

This article was a systematic review and meta-analysis of published studies, not a new study of workers. The authors pooled risk estimates for lung cancer and head and neck cancer among people exposed to man-made vitreous fibers (MMVF), mainly rock wool and glass wool (fiberglass). Across 16 lung cancer estimates (1662 exposed cases), the summary relative risk was 1.21 (95% confidence interval 1.11 to 1.32). It was 1.26 (1.10 to 1.44) for production workers, with similar figures for rock wool and glass wool workers. It was 1.06 (0.77 to 1.48) for end users and 1.18 (0.98 to 1.42) in community-based studies. For head and neck cancer, six estimates (414 cases) gave 1.36 (1.13 to 1.63). With a few exceptions, studies that looked at the amount of exposure found no dose-risk relation. No clear excess of pleural mesothelioma had been reported. The authors noted that most studies lacked quantitative exposure measurement. They concluded that a credible causal connection between MMVF and lung cancer could not be drawn, and that similar conclusions applied to head and neck cancer.

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: Systematic review and meta-analysis (random-effects model) of published epidemiologic studies
• Who was studied: Published epidemiologic studies found through PubMed with no limits on year or language. They included cohort studies of rock wool and glass wool production workers (USA, Europe, Canada, France), studies of applicators and other end users (Sweden, France), and community-based case-control studies. The pooled analyses used 16 lung cancer risk estimates and 6 head and neck cancer risk estimates.
• Exposure: Man-made vitreous fibers (MMVF): rock wool (stone wool, with slag wool combined into rock wool), glass wool (fiberglass), and in some studies continuous glass filament reported as part of MMVF as a group. The exposure settings were production, application and other end uses, and exposures assessed in community-based studies.
• Main results:
  • Lung cancer, all studies: summary relative risk 1.21 (95% CI 1.11 to 1.32), based on 16 risk estimates and 1662 exposed cases.
  • Lung cancer, production workers: summary relative risk 1.26 (95% CI 1.10 to 1.44). The figure was 1.32 (1.15 to 1.53) for rock wool workers (198 cases) and 1.22 (1.00 to 1.49) for glass wool workers.
  • Lung cancer, end users: summary relative risk 1.06 (95% CI 0.77 to 1.48). Community-based studies: 1.18 (95% CI 0.98 to 1.42).
  • Head and neck cancer, all studies: summary relative risk 1.36 (95% CI 1.13 to 1.63), based on 6 risk estimates and 414 cases.
  • Head and neck cancer by site: summary relative risk 1.32 (95% CI 1.09 to 1.59) for oral and pharyngeal cancer and 1.33 (95% CI 1.08 to 1.64) for laryngeal cancer.
  • With a few exceptions, the studies that examined lung or head and neck cancer by measures of MMVF exposure did not detect a dose-risk relation.
  • There was limited evidence that tobacco smoking confounded the results.
  • In the reviewed studies, no clear excess of pleural mesothelioma had been reported in MMVF-exposed workers. This was reviewed, not meta-analyzed.
• The authors' conclusion: The authors concluded that, at the present time, a credible causal connection between MMVF and lung cancer risk could not be drawn, and that similar conclusions applied to head and neck cancer risk among MMVF-exposed workers.
• Limitations the authors state:
  • Most studies lacked quantitative exposure assessment and had inadequate data on confounders such as smoking, asbestos exposure and socioeconomic factors.
  • There were too few studies to do a quantitative meta-analysis of pleural mesothelioma or sinonasal cancer.
  • Several studies reported results only for MMVF as a group, which also included continuous glass filament.
  • Reporting or publication bias may have affected the head and neck cancer results.
  • Most studies did not address confounding by heavy alcohol drinking for head and neck cancer.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Systematic Review, Meta-Analysis, Vitreous, Lung Cancer, Relative Risk, Confounding, Pleural Mesothelioma.

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