Review of refractory ceramic fiber (RCF) toxicity, epidemiology and occupational exposure

Abstract

This literature review on refractory ceramic fibers (RCF) summarizes relevant information on manufacturing, processing, applications, occupational exposure, toxicology and epidemiology studies. Rodent toxicology studies conducted in the 1980s showed that RCF caused fibrosis, lung cancer and mesothelioma. Interpretation of these studies was difficult for various reasons (e.g. overload in chronic inhalation bioassays), but spurred the development of a comprehensive product stewardship program under EPA and later OSHA oversight. Epidemiology studies (both morbidity and mortality) were undertaken to learn more about possible health effects resulting from occupational exposure. No chronic animal bioassay studies on RCF have been conducted since the 1980s. The results of the ongoing epidemiology studies confirm that occupational exposure to RCF is associated with the development of pleural plaques and minor decrements in lung function, but no interstitial fibrosis or incremental lung cancer. Evidence supporting a finding that urinary tumors are associated with RCF exposure remains, but is weaker. One reported, but unconfirmed, mesothelioma was found in an individual with prior occupational asbestos exposure. An elevated SMR for leukemia was found, but was absent in the highly exposed group and has not been observed in studies of other mineral fibers. The industry will continue the product stewardship program including the mortality study.

Keywords:

• Classification
• epidemiology
• refractory ceramic fiber
• toxicology
• pleural plaques occupational exposure
• Product Stewardship Program
• Recommended Exposure Guideline

Acknowledgements

We would like to acknowledge the helpful contributions of Mr Ronald Niebo, Everest Consulting Associates and useful comments by referees and Prof. Dr Med. Helmut Greim, Director of the Institute of Toxicology and Environmental Hygiene, Technische Universität München.

Disclosure statement

The authors performed this work as independent consultants. Both authors serve as consultants on a scientific review board for Unifrax, a major producer of HTIWs and have performed studies for the HTIW Coalition. Neither author has appeared in any legal or regulatory proceeding relative to RCF. The findings and conclusions are those of the authors alone and do not necessarily represent the views of the sponsor.

This research was sponsored by the HTIW Coalition (see http://www.htiwcoalition.org/for a list of members and associate members), an organization that focuses on health and safety matters for producers of RCF and other high-temperature insulating wools (HTIWs) in the US.