ENVIRONMENTAL RESEARCH 22. 499-509 (1980) A Model for the Exposure of Individual Lung Cells to the Foreign Elements Contained in Fly Ash THOMAS L. HAYES,” JAMES B. PAWLEY,*.’ GERALD L. FISHER,~,~ AND MARVIN GOLDMAN? Received November 19. 1979 The exposure of the individual cells of lung tissue to the chemical elements associated with fly ash particles is a very sensitive function of the elemental distribution among indi- vidual particles. There is evidence that the individual particle chemistry is not homogeneous with respect to major element composition among particles and that many of the elements are found in high concentration in a few particles rather than existing in relatively uniform concentration among all of the particles. This segregation of elements in specific particles results in the possibility for significantly higher exposure levels within individual cells than those projected from the model of the elemental concentrations distributed uniformly among the particles. INTRODUCTION Fly ash produced by coal-burning power plants is a major component of airborne particles associated with electrical energy production. It has been projected that in 1980, United States power plants will generate 100 million tons of fly ash of which l-5% will be released to the atmosphere (Fisher rt al.. 1979a). In the majority of studies of the chemical elements associated with fly ash particles, the analyses have involved averaging the elemental chemistry over large numbers of particles. For example, neutron activation analysis (NAA) and atomic absorption analysis (AAA) have often been employed (Natusch et al., 1975; Coles et al., 1979). In this type of analysis, the overall chemical composition of the sample can be determined very accurately but variations in elemental composition among individual particles cannot be assessed. Biological effects of particulate contaminants are initiated at the cellular level and while certain of these effects are only important when large numbers of cells are affected, other biological consequences (e.g., mutagenesis, carcinogenesis) are probably initiated by changes in a single cell or a small group of cells. Some of the chemical elements found in bulk samples of fly ash (e.g., As, Cd, Cr, and Ni) are known to be human carcinogens and the mutagenicity of filtrates from respira- ble coal fly ash has been demonstrated (Chrisp et al., 1978; Fisher et al., 1979 a). Cellular contact with the pollutant particle can be due to adsorption on the cell I Present address: HVEM Factlity. Animal Sciences Building, Observatory Dr., University of Wis- consin, Madison, Wis. 53706. z Present address: Toxicology-Pharmacology Section, Battelle Columbus Laboratories. 505 King Ave., Columbus, Oh. 43201. 499 00 13-935 l/80/040499- I 1$02.00/O Copyright @ I ! 1980 by Academic Press. Inc. All rights of reproducrion m any form reserved