Toxicity of C, C, C, and CPolychlorinated alkanes to Japanese medaka (Oryzias latipes) embryos

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Abstract
Japanese medaka (Oryzias latipes) eggs were exposed to aqueous concentrations of six polychlorinated n‐alkane (PCA) standards (C10H155Cl65, C10H153Cl67, C11H184Cl56, C12H195Cl65, C14H24,9Cl5.1, and C14H23, 3Cl67) of known carbon chain length and chlorine content to assess their toxicity. Eggs were also exposed to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) to act as a positive control. Chlorinated paraffins are complex industrial products for which there is a lack of toxicological data on individual congeners. High aqueous concentrations of C10H155Cl65 and C10H15,3Cl6,7 (9,600 and 7,700 ng/ml, respectively) caused 100% mortality in eggs, but no other significant mortalities or lesions were observed at lower concentrations or in any eggs exposed to the other PCAs. Larvae from eggs exposed to high concentrations of the C10‐, C11‐ and C12‐PCAs were extremely lethargic or did not move, although a heart beat was present. The concentrations in these exposures and the tissue concentrations of the larvae were at levels that should elicit narcosis. Concentrations of the C14‐PCAs in larvae did not reach narcotic levels, and larvae in these exposures appeared normal with no signs of narcosis. The TCDD was found to be extremely embryotoxic, consistent with past work using Japanese medaka eggs. The ratio of LC50 of TCDD to the LC50 of the PCAs, based on acute toxicity and TCDD results, were all 10‐13) and medium (C14‐18) carbon chain PCAs is narcosis and that chlorine substitution on the terminal carbons of PCAs does not significantly increase nor decrease the toxicity of C10‐ and C14‐PCAs. However, additional work is needed to assess a greater range of PCAs as well as their sublethal effects and chronic toxicity.

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