Bioconcentration, biotransformation, and chronic toxicity of sodium laurate to zebrafish (Danio rerio)

Abstract The chronic toxicity of sodium laurate (dodecanoic acid, sodium salt; CAS 629-25-4) to zebrafish (Danio rerio) was determined in a 28-d growth rate study. The laurate did cause lethal effects, but a reduction in growth was not observed at sublethal exposure concentrations. The 15-d median lethal concentration was 7.6 mg/L, which is similar to the theoretical and measured solubility limit of laurate under the test conditions. The 28-d no-observed-effect concentration (lethality) was 2 mg/L, whereas growth was not impaired at 6.4 mg/L in survivors after 28 d. Laurate was extensively biotransformed to metabolites, including less polar compounds, possibly triacylglycerols. At the end of the exposure period, which was considered long enough for steady state to be achieved, the bioconcentration factor of laurate was estimated to be 255 L/kg. Body burdens of nonmetabolized laurate for surviving fish were up to 10-fold higher (2.7–8.7 mmol/kg) than the chronic critical (sublethal) body residues (0.2–0.8 mmol/ kg) proposed for nonpolar or polar narcotics.