Synthetic Vitreous Fibers: A Review Toxicology, Epidemiology and Regulations

Abstract

This review addresses the characteristics which differentiate synthetic vitreous fibers (SVFs, e.g., fiber glass, stonewool, slagwool, refractory ceramic fibers, etc.), how these influence the potential biopersistence and toxicity, the most recent epidemiological results and the integration of these findings into the health and safety regulations in Europe and the United States. Also presented is the historical basis for the European classification directive. The use and equivalence of the chronic inhalation toxicology and chronic intraperitoneal injection studies in laboratory rodents for evaluation of fiber toxicology is assessed as well as the impact of dose selection and design on the validity of the study. While synthetic vitreous fibers can span a wide range of chemistries, recognition and understanding of the importance of biopersistence (ability to persist in the lung) in fiber toxicity has led to the development of more and more biosoluble fibers (that break down rapidly in the lung). Still, the epidemiological data available which are largely based upon the use of fibers in past decades, indicate that the SVF do not present a human health risk at current exposure levels. The animal toxicology and biopersistence data provide a coherent basis for understanding and evaluating the parameters which affect SVF toxicity. The current regulations are based upon an extensive knowledge base of chronic studies in laboratory rodents which confirm the relationship between chronic adverse effects and the biopersistence of the longer fibers that can not be fully phagocytised and efficiently cleared from the lung. The amorphous structure of synthetic vitreous fibers facilitates designing fibers in use today with low biopersistence. Both the epidemiological data and the animal studies database provide strong assurance that there is little if any health risk associated with the use of SVFs of low biopersistence. IARC (2001) reclassified these fibers from Category 2b to Category 3 (with RCF and special purpose fibers remaining in 2b) an event which has not been common in the history of these monographs.

Key words :

• Synthetic Vitreous Fibers
• Man-Made Vitreous Fibers
• Inhalation Toxicology
• Epidemiology
• Regulatory
• Glasswool
• Stonewool
• Slagwool
• Refractory Ceramic Fibers
• Biopersistence
• European Classification
• US EPA Integrated Risk Information System

Notes

²EURIMA: European Insulation Wool Manufacturers Association Insulation www.eurima.org

³ECFIA: European Ceramic Fibers Industry Association www.ecfia.org

⁴APFE: European Glass Fiber Producers Association, 89 avenue Louise, B-1050 Brussels

⁵Annex VI (2001) Section 4.2.1 Carcinogenic substances: For the purpose of classification and labelling, and having regard to the current state of knowledge, such substances are divided into three categories:

• Category 1: Substances known to be carcinogenic to man. There is sufficient evidence to establish a causal association between human exposure to a substance and the development of cancer.

• Category 2: Substances which should be regarded as if they are carcinogenic to man. There is sufficient evidence to provide a strong presumption that human exposure to a substance may result in the development of cancer, generally on the basis of:

  • appropriate long-term animal studies,

  • other relevant information.

• Category 3: Substances which cause concern for man owing to possible carcinogenic effects but in respect of which the available information is not adequate for making a satisfactory assessment. There is some evidence from appropriate animal studies, but this is insufficient to place the substance in category 2.

⁶Chemikalienverbots-Verordnung vom 25. Juni 2003 (BGBl. I Nr. 26, zuletzt geändert durch Artikel 1 der neunten Verordnung zur Änderung chemikalienrechtlicher Verordnungen im Bundesgesetzblatt Jahrgang 2004 Teil I Nr. 76 ausgegeben zu Bonn am 31. Dez. 2004) Chemical prohibition regulation of June 25, 2003 [BGBl. I Number 26, most recently revised by article 2 of the ninth regulation for the change of chemical law regulations in federal papers of the year 2004, part 1, Number 76, published in Bonn on December 31, 2004])

⁷RAL Deutsches Institut für Gütesicherung und Kennzeichnung e. V. (RAL German Institute for Quality Assurance and Marking Registered Association)

⁸Technische Regel für Gefahrstoffe TRGS 521, Teil 1 u. Anlagen 1–5, BArbBl. 5/02 (Technical Rules for Dangerous materials TRGS 521, Part 1 and Exhibits 1–5, BArbBl. 5/02)

⁹Technische Regel für Gefahrstoffe TRGS 500, BArbBl. 3/98 (Technical Rules for Dangerous Materials TRGS 500, BArbBl. 3/98)