TOXICOLOGICAL ASSESSMENT OF BIOTRANSFORMATION PRODUCTS OF PENTACHLOROPHENOL - TETRAHYMENA POPULATION-GROWTH IMPAIRMENT

Pentachlorophenol (PCP) is a widespread contaminate of soils and groun d water throughout North America. Earlier studies have indicated that microbial biodegradation leads to the formation of intermediate metabo lites which are more toxic than the parent compound. Microbial degrada tion is by three general pathways: dechlorination, methylation, and ox idation. The relative toxicity of PCP and 25 of its identified interme diates of microbial transformation was evaluated in the static Tetrahy mena pyriformis population growth assay. Dechlorination of chloropheno ls resulted in a decrease in toxicity because of a decrease in both hy drophobicity and reactivity. Moreover, dechlorination of chloroanisole s resulted in a decrease in toxicity due to a decrease in hydrophobici ty. Since there was a decrease in reactivity, methylation of chlorophe nols resulted in a decrease in toxicity. Oxidation of chlorophenols re sulted in enhanced toxicity owing to increased reactivity and concomit ant decreased hydrophobicity.