A systematic review of occupational exposure to synthetic vitreous fibers and mesothelioma

Abstract

Objective We investigated whether available epidemiological and toxicological data suggest an increased risk of mesothelioma among workers exposed to synthetic vitreous fibers (SVF). Methods We conducted a systematic review of epidemiological studies on the risk of mesothelioma among workers exposed to SVF, and toxicological studies on SVF and mesothelioma. Results Seven cohort studies were conducted among workers employed in production of rock/slag wool, glass wool, or continuous glass filament in the United States, Canada, and Europe. Of the six deaths from mesothelioma identified in these studies, three had exposure to asbestos. A review of death certificates in a study of rock wool production workers identified one additional probable death. A formal comparison with expected deaths is not feasible. Four community-based case–control studies were identified, of which three reported an increased risk among SVF-exposed workers. The number of cases not exposed to asbestos was less, and residual confounding from asbestos exposure misclassification may explain the association in these studies. The toxicology review of SVF suggested that they present a low hazard mostly due to their low biopersistence, typically with a half-life in rat studies of tens of days compared to amphibole asbestos which has a half-life of 400–500 days. Conclusions The combined evidence from epidemiology and toxicology provide little evidence that exposure to SVF increases the risk of mesothelioma.

Keywords:

• biopersistence
• epidemiology
• mesothelioma
• misclassification
• occupational
• toxicology
• synthetic vitreous fibers

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

This study was supported under a contract from EURIMA (European Insulation Manufacturers Association) to Exponent Inc. PB and KD were compensated by Exponent, Inc. EURIMA played no role in the design and conduct of the study nor in the preparation of the manuscript. KD has carried out paid consultancy for the SVF industry in the form of written reports regarding the toxicology of SVF in relation to safety and regulation. He is a Trustee of the Joint European Medical Research Board of the European Insulation Manufacturers Association that promotes research into the safety of the European SVF industry's products. He has made representation on behalf of the SVF industry regarding the toxicology of SVF to regulatory bodies and interested groups in a number of countries for which he received financial remuneration. KD has also carried out paid consultancy for the asbestos industry. SM serves as an expert defense witness in asbestos litigation. He is a consultant to WR Grace and has served as a consultant to the Refractory Ceramic Fibers Coalition. PB has given testimony in an asbestos case. JM consults industry and has consulted on asbestos issues. The design and conduct of the literature review and the synthesis of the findings and conclusions drawn are exclusive work carried out professionally by the authors.