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plants (and identified as such) are included briefly, sometimes to complete a survey of silicone species and other times because they have been mentioned in the current debate on the toxic effects of implants. It is important to note that toxicology studies often report silicone dose levels substantially in excess of any doses that could be achieved on a relative weight basis in women with silicone breast implants.

Earlier in this report, the committee emphasizes the relevance of published, peer-reviewed scientific reports and assigns secondary importance to technical reports from industry. In this chapter, however, studies done in-house by industry or by commercial testing laboratories have been analyzed. Such reports are often reviewed first in-house, then by the sponsor and panels of outside experts, and eventually by a regulatory agency, which also looks at original data. The conflict of interest inherent in experimentation by an organization with an economic interest in the outcome is recognized. Nevertheless, the committee found many of industry's technical studies informative, useful, and consistent with sound science. The studies cited here consisted of about 50 individual articles from the open scientific literature between 1948 and 1999 and about the same number of industry technical reports. Reviews available to the committee summarized data from some reports not reviewed by or not available to the committee. For example, the Silicones Environmental Health and Safety Council (1995) examined may reports on various organic silicon compounds that are not found in breast implants and reviewed some reports not accessible to the committee. This review was useful in presenting an overall picture of the generally low toxicity of silicones and identifying particular compounds that had toxicity. The report of the Independent Review Group (IRG, 1998) (and earlier versions of the Medical Devices Agency's work), and the report of the National Science Panel (Kerkvliet, 1998) which are described in Appendix C looked at essentially the same body of toxicology information as the committee. The IRG report included proprietary data not available to the committee, and as noted, the committee examined routes of exposure and listed silica references neither of which are included in the IRG or National Science Panel reports. Since the IRG, which had some proprietary data, concluded that silicones were bland substances with little toxicity, such data seem unlikely to have changed the committee's findings in any substantial way. Also, the committee believes that the inclusion of dermal, oral and inhalation toxicology studies in this report provided additional security in conclusions about the biological and toxicological behavior of relevant silicones.

Kerkvliet lists three major reasons why toxicology studies are helpful in assessing the safety of a drug or consumer product such as silicone breast implants. (1) Toxicology studies in animals may identify a haz-



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