Toxicity of hydroxylated alkyl-phenanthrenes to the early life stages of Japanese medaka (Oryzias latipes)

Polycyclic aromatic hydrocarbons (PAH) are hydrophobic environmental contaminants with petrogenic, biogenic, and pyrogenic sources. Alkylated PAH predominate in crude oils, are found in sediment downstream of pulp and paper mills, and can be more toxic than their non-alkylated homologues. The enzymatic metabolism of alkyl phenanthrenes generates ring and chain hydroxylated derivatives. The main objective of this research was to estimate the potential role of hydroxylation in PAH toxicity and secondly to better understand the relative risk of different PAH in complex mixtures. This project assessed the toxicity of ring and chain hydroxylated 1-methylphenanthrenes to the early life stages of Japanese medaka (Oryzias latipes). Phenols were more toxic than benzylic alcohols, and some phenols were more than four times more toxic than their non-hydroxylated counterpart. Ring hydroxylation can increase PAH toxicity, and metabolism may enhance alkyl-PAH toxicity through the generation of such metabolites. This paper is the first to describe the relative toxicity of a suite of hydroxylated alkyl-PAH to the early life stages of fish, proposing an association between the preferential formation of para-quinones and enhanced toxicity.

► Ring hydroxylation increased the toxicity of 1-methyl phenanthrene to Japanese medaka.
► The most toxic congeners were hydroxylated in the 7 and 8 positions and could form para-quinones if subjected to further hydroxylation.
► Chain hydroxylation did not change 1-methyl phenanthrene toxicity.
► The toxicities of six hydroxylated 1-methylphenanthrenes was unrelated to octanol–water partition coefficient.