DIOXINLIKE PROPERTIES OF A TRICHLOROETHYLENE COMBUSTION-GENERATED AEROSOL

Conventional chemical analyses of incineration by-products identify co mpounds of known toxicity but often fail to indicate the presence of o ther chemicals that may pose health risks. In a previous report, extra cts from soot aerosols formed during incomplete combustion of trichlor oethylene (TCE) and pyrolysis of plastics exhibited a dioxinlike respo nse when subjected to a keratinocyte assay. To verify this dioxinlike effect, the complete extract, its polar and nonpolar fractions, some c ontaining primarily halogenated aromatic hydrocarbons, were evaluated for toxicity using an embryo assay, for antiestrogenicity using primar y liver cell cultures, and for the ability to transform the aryl hydro carbon receptor into its DNA binding form using liver cytosol in a gel retardation assay. Each of these assays detect dioxinlike effects. Me daka (Oryzias latipes) embryos and primary liver cell cultures of rain bow trout (Oncorhynchus mykiss) were exposed to concentrations of extr act ranging from 0.05 to 45 mu g/l. Cardiotoxicity with pericardial, y olk sac, and adjacent peritoneal edema occurred after exposure of embr yos to concentrations of 7 mu g/l or greater. These same exposure leve ls were associated with abnormal embryo development and, at the higher concentrations, death. Some of the fractions were toxic but none was as toxic as the whole extract. In liver cells, total cellular protein and cellular lactate dehydrogenase activity were not altered by in vit ro exposure to whole extract (0.05-25 mu g/l). However, induction of c ytochrome P4501A1 protein and ethoxyresorufin O-deethylase activity oc curred. In the presence of whole extract, estradiol-dependent vitellog enin synthesis was reduced. Of the fractions, only fraction 1 (nonpola r) showed a similar trend, although vitellogenin synthesis inhibition was not significant. The soot extract and fractions bound to the Ah re ceptor and showed a significantly positive result in the gel retardati on/DNA binding test. Chemical analyses using GC-MS with detection limi ts for 2,3,7,8-tetrachlorodibenzo-p-dioxin and dibenzofuran in the pic omole range did not show presence of these compounds. Our results indi cate that other chemicals associated with TCE combustion and not origi nally targeted for analysis may also pose health risks through dioxinl ike mechanisms.