Environmental Health Perspectives 105, Supplement 5, September 1997

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Use of Mechanistic Data in Assessing Human Risks from Exposure to Particles

Roger O. McClellan

Chemical Industry Institute of Toxicology, Research Triangle Park, North Carolina

Abstract
The ultimate goal of toxicologic investigations of both natural and man-made fibrous and nonfibrous particles is to provide essential input for the assessment of potential human risks from exposure to these materials. The development of risk assessment procedures for airborne particles has evolved over the years. The earliest assessments for naturally occurring materials used direct human observations and incorporated safety factors to arrive at allowable human exposures. More recently, there has been a need to assess the potential risk associated with production and use of certain man-made materials for which human data are not available or are inadequate. For these materials, it has been necessary to assess human risks using data obtained from studies conducted in laboratory animals and with cells or tissues. During the last several decades, it has been suggested that data on the mechanisms by which particles cause disease could be used to reduce the uncertainty in estimates of human risks of particle exposures. This article provides comments on the use of mechanistic data in the risk assessment process and suggestions for increasing the successful development and use of mechanistic data in risk assessments conducted in the future. -- Environ Health Perspect 105(Suppl 5):1363-1372 (1997)

Key words : risk assessment, particles, fibers, toxicity, cancer

This paper is based on a presentation at The Sixth International Meeting on the Toxicology of Natural and Man-Made Fibrous and Non-Fibrous Particles held 15-18 September 1996 in Lake Placid, New York. Manuscript received at EHP 26 March 1997; accepted 9 July 1997.

The assistance of my colleagues in preparing the manuscript is gratefully acknowledged: L. Smith for word processing, S. Piestrak for graphics, B. Kuyper for scientific editing, and J. Bond and R. Conolly for their critical review and useful comments.

Address correspondence to Dr. R.O. McClellan, Chemical Industry Institute of Toxicology, P.O. Box 12137, 6 Davis Drive, Research Triangle Park, NC 27709. Telephone: (919) 558-1202. Fax: (919) 558-1400. E-mail: mcclellan@ciit.org

Abbreviations used: ACGIH, American Conference of Governmental Industrial Hygienists; CAA, Clean Air Act; CASAC, Clean Air Scientific Advisory Committee; HAP, hazardous air pollutant(s); IARC, International Agency for Research on Cancer; NAAQS, National Ambient Air Quality Standard(s); NRC, National Research Council; NTP, U.S. National Toxicology Program; OSHA, Occupational Safety and Health Administration; PEL, permissible exposure limit(s); PM, particulate matter; PM 2.5 , particulate matter=2.5 µm in aerodynamic diameter; PM 10 , particulate matterLess than or = to10 µm in aerodynamic diameter; RfC, reference concentrations; TLV, threshold limit value(s); TSCA, Toxic Substances Control Act; TSP, total suspended particulate(s); TWA, time-weighted average(s); U.S. EPA, U.S. Environmental Protection Agency.

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Last Update: November 28, 1997