The North American Insulation Manufacturers’ Association (NAIMA) suffered a major setback in 1994, when its attempt to block inclusion of man-made mineral fibres (MMMF) in the US National Toxicology Program’s Annual Report of Carcinogens (ARC) failed. NAIMA has submitted a petition to the Secretary of Human Services opposing the move. In response, scientists with the federation workplace safety regulator OSHA reviewed the evidence. They were critical of evidence used in the company’s defence, particularly industry sponsored animal studies by Thomas Hesterberg which concluded glass fibres do not cause cancer. The OSHA scientists highlighted several major deficiencies in the Hesterberg animal experiments, and also contested the negative conclusions reached. Following its review of both animal and human data, they concluded that glass fibres should be classified as carcinogenic, noting “that on a fiber-per-fiber basis, glass fibers may be as potent or even more potent than asbestos.” The NAIMA petition was denied and glass fibre was listed in the ARC as being “reasonably anticipated to cause cancer in humans.” Thomas Hesterberg later turned his attention to the asbestos industry and gave evidence against an asbestos ban before the Supreme Court in Brazil in 2012 and was a contributor at an asbestos industry promotional conference in India in 2013. In November 2013, he was named in a list of “scientists who help asbestos industry sell asbestos.”

PE Infante and others. Fibrous glass and cancer, American Journal of Industrial Medicine, volume 26, pages 559-584, 1994.
TW Hesterberg and others. Chronic inhalation study of size-separated glass fibers in Fischer 344 rats, Fundamental and Applied Toxicology, volume 20, pages 464-476, 1993.