Evaluation of the OECD P and LRTP screening tool for estimating the long-range transport of organophosphate esters.

Scientists and decision makers need accurate, accessible and fast tools to assess and prioritize the persistence (P) and environmental long-range transport potential (LRTP) of chemicals. Here we evaluated the Organisation for Economic Co-operation and Development (OECD) P and LRTP Screening Tool ("the Tool") with respect to the P and LRTP estimates that the Tool provides for organophosphate esters (OPEs). We found that the use of default parameter values could significantly underestimate P and LRTP values of OPEs and, potentially, other Persistent Mobile Organic Compounds (PMOCs), by not accounting for episodic atmospheric transport and poleward river-based transport in the northern hemisphere. Specifically, sensitivity and Monte Carlo uncertainty analyses indicate that non-chlorinated OPEs could be subject to LRTP when uncertainties in gas-particle partitioning and its implications for atmospheric degradation are considered, and chlorinated OPEs when river-based transport is considered. Further, the analyses showed strong dependence of results on the accuracy of the environmental half-lives used as input parameters. We suggest that the Tool could be modified to include an optional "Arctic (PMOC) LRTP setting" that incorporates episodic atmospheric and river-based transport as well as decreased environmental half-lives due to cold temperatures.