Subclinical and reversible hepatic effects of occupational exposure to trichloroethylene

To detect early hepatic effects of chronic exposure to low-level trichloroethylene (TCE), serum total cholesterol (T-C), high-density-lipoprotein cholesterol (HDL-C) and activities of three serum enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transpeptidase (GGT)] were determined in 148 workers (a cross-sectional study) and in 13 workers (a 2-year follow-up study) occupationally exposed to TCE in air. In the cross-sectional study, three exposure groups were defined by urinary total trichloro-compounds (U-TTC) levels of the workers [low-exposure group (n = 49): U-TTC < 10 mg/g creatinine; moderate-exposure group (n = 56): U-TTC 10- < 100; high-exposure group (n = 43): U-TTC > or = 100]. With increasing exposure levels, T-C (P = 0.143 by ANOVA) and HDL-C (P = 0.080 by ANOVA) slightly increased. The exposure, however, had no effect on the activities of the three serum enzymes. In the follow-up study, the fluctuations in U-TTC were well reflected in subclinical changes in HDL-C, AST, and GGT, but not in T-C or ALT. These results suggest that exposure to low-level TCE influences hepatic functions, affecting cholesterol metabolism rather than causing hepatic cell damage, and that these influences are subclinical and reversible. The increases in HDL-C caused by exposure to low-level TCE may be an example of "chemical hormesis" in humans.