Quantitative Structure Activity Relationships for chronic toxicity of alkyl-benz[a]anthracenes to early life-stages Japanese medaka (Oryzias latipes)
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Polycyclic aromatic hydrocarbons (PAH) are hydrophobic environmental contaminants known to impact survival and reproduction in fish species. This study tested the toxicity of benz[a]anthracene (B[a]A) and 7-methylbenz[a]anthracene (7-MeB[a]A) to early life stages of Japanese medaka (Oryzias latipes) using the partition controlled delivery (PCD) method of exposure and the relationship between toxicity and the log of octanol- water partition coefficient (log P). The exposure method PCD provides stable exposure concentrations maintained at and below the solubility limit of test chemicals throughout chronic toxicity assays. It relies on the partitioning of the test chemical from prepared poly (dimethylsiloxane) (PDMS) films, loaded with various concentrations of chemical, to the exposure solution. Aqueous solubility limits and film: solution partition coefficients (log Kfs) were determined. The prevalence of blue sac disease (BSD) in exposed medaka embryos was used to determine median effective concentration (EC50) of the two congeners. The test chemical 7-MeB[a]A was more toxic than B[a]A, and toxicity increased with log P. These results will further contribute to models for assessing the risk of PAH mixtures as well as to our understanding of how toxicity is affected by alkylation.