Systematic review and meta-analysis of the epidemiology of man-made vitreous fibres and respiratory health outcomes.

Objectives: The generic term man-made vitreous fibres (MMVFs) also known as man-made mineral fibres (MMMFs) denotes non-crystalline, fibrous inorganic material manufactured primarily from glass, rock, minerals, slag, glass, and processed inorganic oxides. The International Agency for Research on Cancer has classified rock (stone) wool, glass wool, and continuous glass filament as Group 3 (not classifiable for carcinogenicity). This study contains an updated systematic review and meta-analysis of respiratory health outcomes and MMMFs.

Methods: Cinahl, EMBASE, Medline, Web of Science, and OpenGrey were searched for epidemiological studies of occupational MMMF exposure and malignant and non-malignant respiratory diseases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were adopted for reporting. Meta-analyses were carried out separately for cohort and case-control studies.

Results: A total of 25 studies were identified for inclusion in the systematic review, with 19 of these (9 cohort; 10 case-control) providing risk estimates for the meta-analyses. Of the cohort studies, 3 were carried out in Sweden, 2 each in Canada and the United States, one in France, and one several European countries. The start of follow-up ranged from 1933 to 1975. The meta-RR for lung cancer from cohort studies (incidence or mortality) was 1.15 (95% CI: 1.01 to 1.32), for laryngeal cancer was 1.03 (95% CI: 0.78 to 1.37), and for non-malignant respiratory diseases (NMRD) mortality was 0.89 (95% CI: 0.66 to 1.22). Of the case-control studies, 9 examined lung cancer and one laryngeal cancer. Three of the lung cancer studies were carried out in France and one each in Germany, Russia, Canada, and China, with one in several European countries and one was a nested case-control study of several case cohorts from across the globe. The meta-OR for lung cancer from the case-control studies was 1.28 (95% CI: 1.10 to 1.50).

Conclusions: Our findings broadly agree with a previously published meta-analysis of respiratory system cancers, in that they were similar in terms of magnitude of relative risk. However, overall, our results suggest that exposure to MMMFs is associated with a small, but statistically significantly elevated risk for lung cancer, but not for laryngeal cancer or NMRDs. Given the heterogeneity between studies, and the possibility of residual confounding, further work is required to determine if this association is causal.