Workshop on fiber toxicology research needs.

A great deal of toxicological and epidemiological data are available for asbestos and a wide variety of other mineral and manmade fibers. Experimental animal data suggest that certain fiber characteristics are responsible for observed biological effects such as cancer. An important fiber characteristic appears to be fiber size (length, diameter, aspect ratio); however, other characteristics such as in vivo persistence and durability, chemical composition, and surface chemistry (surface charge, etc.) may also be important, although less well studied. Studies involving intrapleural or intraperitoneal im-plantation or injection have been most useful in determining fiber characteristics responsible for carcinogenic response; however, these studies may have limited utility in predicting actual human risks. Intrapleural models bypass normal lung defense mechanisms and related cell/fiber interactions. In vivo persistence, or the ability of the inhaled fiber to stay in the biological environment where introduced, is thought to be an important but not well-studied parameter that could explain the different responses seen by intrapleural versus inhalation studies. Considerably more research is needed to more precisely identify mechanisms for fiber-induced disease and related fiber characteristics. To help define areas for further research, a workshop concerning "Fiber Toxicology Research Needs" sponsored by the National Institute of Environmental Health Sciences (NIEHS) was held in Research Triangle Park, NC from July 10 to 12, 1989. The workshop brought together international experts in environmental science, industrial hygiene, epidemiology , toxicology, and molecular biology. Objectives of the workshop were to critically review human and experimental data concerning fiber toxicology with an emphasis on biological mechanisms; identify data gaps and research needs; and suggest future research efforts. In preparation for the workshop, critical review papers were prepared and distributed to conference participants. These review papers were presented and discussed during the first day of the workshop. During the second day participants were divided into four subgroups that addressed research needs in the areas of exposure assessment, in vitro studies, animal toxicology studies, and human epidemiology. The workshop's final day consisted of presentations and discussions of research recommendations developed during the four concurrent sessions. The critical review papers are published in this volume. The following are reports from each of the subgroups. Current Issues. FIBER SAMPLING. One of the sampling methods currently used for the collection of fibrous aerosol samples in the workplace uses inlet cowls in conjunction with membrane ifiter sample holders. The use of a cowl was intended to enhance the uniformity …