Marine pharmaceutical monitoring with POCIS: sampling rate uncertainty, and implications for regulation

POCIS passive samplers were deployed at differently polluted marine sites in the cities of Helsinki and Tallinn and in an open part of the Gulf of Finland. The aim was to determine baseline concentration levels for pharmaceuticals in water monitored with passive sampling techniques, which could also be applied to regulatory monitoring. That baseline concentration data method could then be applied to other sites in the Tallinn and Helsinki area to assess whether the pharmaceutical concentration is elevated or at the baseline level. Altogether, 150 pharmaceuticals were analysed from passive and grab water samples, and 30 substances were discovered. The number of pharmaceuticals detected in passive samplers (27) was higher than in grab samples (20). However, the study revealed the presence of several pharmaceuticals even from expected background sites, such as the open sea site in Gulf of Finland, implying their ubiquitous presence in the study area. The passive sampling results have been converted to TWAC with sampling rate, which is characteristic of the sampler type and studied compound. We assessed the suitability and differences of sampling rates collected from the literature, calculated from LogK_OW values and estimated from field deployment results. The selection of sampling rate is essential, as it can cause 86 to 99% differences in determined TWACs. The TWAC was compared with PNEC was calculated to evaluate the potential environmental risk. There are still open questions regarding how to reconcile the passive sampling results with regulatory monitoring obligations based on grab water sampling and existing limit concentrations.