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

The chronic toxicity of sodium laurate (dodecanoic acid, sodium salt; CAS 6 29-25-4) to zebrafish (Danio rerio) was determined in a 28-d growth rate st udy. The laurate did cause lethal effects, but a reduction in growth was no t observed at sublethal exposure concentrations. The 15-d median lethal con centration was 7.5 mg/L, which is similar to the theoretical and measured s olubility limit of laurate under the test conditions. The 28-d no-observed- effect concentration (lethality) was 2 mg/L, whereas growth was not impaire d ac 6.4 mg/L in survivors after 28 d. Laurate was extensively biotransform ed to metabolites, including less polar compounds, possibly triacylglycerol s. At the end of the exposure period, which was considered long enough for steady state to be achieved, the bioconcentration factor of laurate was est imated 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.