Dietary Bioaccumulation and Biotransformation of Hydrophobic Organic Sunscreen Agents in Rainbow Trout

The present study investigated the dietary bioaccumulation and biotransformation of hydrophobic organic sunscreen agents, 2-ethylhexyl-4-methoxycinnamate (EHMC) and octocrylene (OCT), in rainbow trout using a modified Organisation for Economic Co-operation and Development 305 dietary bioaccumulation test that incorporated nonbiotransformed reference chemicals. Trout were exposed to 3 dietary concentrations of each chemical to investigate the relationship between dietary exposure concentration and observed accumulation and depuration. Both EHMC and OCT were significantly biotransformed, resulting in mean in vivo whole-body biotransformation rate constants (k_MET ) of 0.54 ± 0.06 and 0.09 ± 0.01 d^-1 , respectively. The k_MET values generated for both chemicals did not differ between dietary exposure concentrations, indicating that chemical concentrations in the fish were not high enough to saturate biotransformation enzymes. Both somatic and luminal biotransformation substantially reduce EHMC and OCT bioaccumulation potential in trout. Biomagnification factors (BMFs) and bioconcentration factors (BCFs) of EHMC averaged 0.0035 kg lipid kg lipid^-1 and 396 L kg^-1 , respectively, whereas those of OCT averaged 0.0084 kg lipid kg lipid^-1 and 1267 L kg^-1 . These values are 1 to 2 orders of magnitude lower than the BMFs and BCFs generated for reference chemicals of similar log K_OW . In addition, for both chemicals, derived BMFs and BCFs fell below established bioaccumulation criteria (1.0 kg lipid kg lipid^-1 and 2000 L kg^-1 , respectively), suggesting that EHMC ad OCT are unlikely to bioaccumulate to a high degree in aquatic biota. Environ Toxicol Chem 2020;39:574-586. © 2019 SETAC.