Fate of organophosphate esters (OPEs) in East Greenland polar bears and their ringed seal prey using in vitro lab- and field-based studies to investigate metabolism

Arctic wildlife can be exposed to environmental chemical contamination due to long-range transport and subsequent deposition. Organophosphate esters (OPEs) are emerging chemicals of concern, found at high concentration in Arctic abiota but low levels in biota, including in polar bear and ringed seal adipose tissue currently under study. OPE metabolism was investigated in East Greenland polar bears and ringed seals using enzymatically-active liver microsomes. Organophosphate triester metabolism rate and extent were found to be greater in polar bears than ringed seals. Chemical structure and physical properties of OPEs affected metabolism; notably, bulkier, alkyl-substituted triphenyl phosphates had decreased metabolism in both species. The degradation of OPEs with aryl and alkyl substituents occurred at a greater rates in polar bears and ringed seals respectively. The structure-dependent metabolism of eleven OPEs have important implications for regulatory and risk assessments, as some compounds have little to no toxicokinetics data available in the current literature.