A year-long study of the spatial occurrence and relative distribution of pharmaceutical residues in sewage effluent, receiving marine waters and marine bivalves

• Pharmaceuticals detected in wastewater effluent at concentrations up to 3.16 μg·g− 1
• Pharmaceuticals detected in Irish marine waters at concentrations up to 1.41 μg·g− 1
• Three pharmaceuticals detected in marine mussels after in situ exposure
• Trimethoprim measured in mussels at concentrations up to 9.22 ng·g− 1 dry weight
• Low risk of pharmaceutical exposure to humans via ingestion of exposed mussels

Reports concerning the quantitative analysis of pharmaceuticals in marine ecosystems are somewhat limited. It is necessary to determine pharmaceutical fate and assess any potential risk of exposure to aquatic species and ultimately, seafood consumers. In the work presented herein, analytical methods were optimised and validated for the quantification of pharmaceutical residues in wastewater effluent, receiving marine waters and marine mussels (Mytilus spp.). Selected pharmaceuticals included two non-steroidal anti-inflammatory drugs (NSAIDs) (diclofenac and mefenamic acid), an antibiotic (trimethoprim), an antiepileptic (carbamazepine) and a lipid regulator (gemfibrozil). This paper also presents the results of an in situ study in which caged Mytilus spp. were deployed at three sites on the Irish coastline over a 1-year period. In water samples, pharmaceutical residues were determined using solid phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS). The extraction of pharmaceuticals from mussel tissues used an additional pressurised liquid extraction (PLE) step prior to SPE and LC–MS/MS. Limits of quantification between 15 and 225 ng·L− 1 were achieved in wastewater effluent, between 3 and 38 ng·L− 1 in marine surface water and between 4 and 29 ng·g− 1 dry weight in marine mussels. Method linearity was achieved for pharmaceuticals in each matrix with correlation coefficients of R2 ≥ 0.976. All five selected pharmaceuticals were quantified in wastewater effluent and marine surface waters. This work has demonstrated the susceptibility of the Mytilus spp. to pharmaceutical exposure following the detection of pharmaceutical residues in the tissues of this mussel species at measurable concentrations.