Product stewardship and science: safe manufacture and use of fiber glass

Our plain-English summary of Product stewardship and science: safe manufacture and use of fiber glass, by T.W. Hesterberg, R. Anderson, D.M. Bernstein, et al (Regulatory Toxicology and Pharmacology, 2012).

The study

• Authors: T.W. Hesterberg, R. Anderson, D.M. Bernstein, W.B. Bunn, G.A. Chase, A.L. Jankousky, G.M. Marsh, R.O. McClellan
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2012;62(2):257-77
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This paper describes a proactive product stewardship program for glass fibers. That effort included epidemiological studies of workers, establishment of stringent workplace exposure limits, liaison with customers on safe use of products and, most importantly, a research program to evaluate the safety of existing glass fiber products and guide development of new even safer products. Chronic inhalation exposure bioassays were conducted with rodents and hamsters. Amosite and crocidolite asbestos produced respiratory tract cancers as did exposure to "biopersistent" synthetic vitreous fibers. "less biopersistent" glass fibers did not cause respiratory tract cancers. Corollary studies demonstrated the role of slow fiber dissolution rates and biopersistence in cancer induction. These results guided development of safer glass fiber products and have been used in Europe to regulate fibers and by IARC and NTP in classifying fibers. IARC concluded special purpose fibers and refractory ceramic fibers are "possibly carcinogenic to humans" and insulation glass wool, continuous glass filament, rock wool and slag wool are "not classifiable as to their carcinogenicity to human." The NTP's 12th report on carcinogens lists "Certain Glass Wool Fibers (Inhalable)" as "reasonably anticipated to be a human carcinogen." "Certain" in the descriptor refers to "biopersistent" glass fibers and excludes "less biopersistent" glass fibers.

Copyright © 2012 Elsevier Inc. All rights reserved.

In plain English

This article was a review, not a new study. It described a Johns Manville and industry product stewardship program and summarized industry-sponsored research. In the chronic inhalation studies it reviewed, rats and Syrian hamsters breathed nine synthetic fiber types for up to two years, with amosite and crocidolite asbestos as positive controls. The amosite and crocidolite groups developed an excess of respiratory tract tumors. So did groups exposed to a special purpose glass fiber (MMVF32) and a refractory ceramic fiber (called RCF1a in the text, RCF1 in a table note). One mesothelioma occurred among 83 hamsters exposed to MMVF33. Five less biopersistent fiber groups, including two insulation glass wools, showed no excess. In short-term rat studies, a substantial fraction of crocidolite fibers stayed in the lungs up to a year, while only a small fraction of a glass wool remained. A cited study reported a relative risk of respiratory system cancer of 1.02 (95% confidence interval 0.76 to 1.34) among female glass wool plant workers, based on four cases. The authors concluded that biopersistence was the key determinant of synthetic vitreous fiber toxicity. Five authors disclosed employment by Johns Manville.

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: Narrative review of an industry product stewardship and research program on glass fibers (epidemiology, animal inhalation studies, biopersistence and in vitro studies, and carcinogen classifications)
• Who was studied: Reviewed animal studies in rats and Syrian hamsters exposed nose-only for up to two years and then followed for life; the review also summarized earlier worker mortality studies
• Exposure: Nine synthetic fiber types (glass wools, special purpose glass fibers, rock, slag and stone wools, refractory ceramic fiber), with amosite and crocidolite asbestos as positive controls; target concentrations for the fiber glass groups were 3, 16 and 30 mg/m3
• Main results:
  • In the reviewed chronic inhalation studies, the amosite and crocidolite asbestos groups developed an excess of respiratory tract tumors
  • An excess of respiratory tract tumors was also seen in groups exposed to MMVF32 (a special purpose glass fiber) and a refractory ceramic fiber
  • The text labels the tumor-producing refractory ceramic fiber RCF1a, but a Table 4 note states that RCF1 was used in the pathogenicity studies and that RCF1a was a modified version with fewer non-fibrous particles
  • With MMVF33 (Special Purpose 475 Glass), no respiratory tract tumors occurred in rats, but one mesothelioma was seen in one of 83 Syrian hamsters
  • Five groups exposed to less biopersistent fibers (MMVF10, X607, MMVF11, MMVF22 and MMVF34) did not have an excess of respiratory tract tumors
  • In 5-day rat biopersistence studies, a substantial fraction of crocidolite fibers was retained for up to a year after exposure ended
  • With MMVF-11 insulation glass wool, only a small fraction of the material remained in the lungs one year after 5 days of exposure
  • Weighted lung clearance half-time correlated with the chronic toxicity produced by the fibers
  • In the reviewed cell culture studies, all fiber compositions were toxic, which the authors interpreted as false positives
  • A cited study (Stone et al. 2004) reported a relative risk of respiratory system cancer of 1.02 (95% confidence interval 0.76 to 1.34) among female workers in glass wool plants
  • That relative risk among female workers was based on four cases in exposed workers
• The authors' conclusion: The authors concluded that biopersistence was the key determinant of the toxicity of synthetic vitreous fibers
• Limitations the authors state:
  • The authors disclosed that five of them were employed by Johns Manville while many of the reviewed studies were conducted, and that others received industry funding or advised the industry program

Topics

Medical terms in this study, explained in our Lexicon: Amosite, Crocidolite, Vitreous, biopersistence, IARC, Carcinogenic.

Related studies

• Chronic inhalation toxicity of size-separated glass fibers in Fischer 344 rats — T.W. Hesterberg, W.C. Miiller, et al. (1993)
• Man-made mineral fiber hazardous properties assessment using transgenic rodents: example of glass fiber testing — M.C. Bottin, J.C. Vigneron, et al. (2003)
• Chronic inhalation study of fiber glass and amosite asbestos in hamsters: twelve-month preliminary results — T.W. Hesterberg, C. Axten, et al. (1997)
• Cytotoxicity, oxidative stress and genotoxicity induced by glass fibers on human alveolar epithelial cell line A549 — V. Rapisarda, C. Loreto, et al. (2015)
• Response of perifused alveolar macrophages to glass fibers: effect of exposure duration and fiber length — G. Forget, M.J. Lacroix, et al. (1986)
• A risk assessment for exposure to glass wool — R. Wilson, A.M. Langer, et al. (1999)

Browse more research in Regulatory Toxicology and Pharmacology, or return to medical research.