ABSTRACT
When assessing the environmental exposure of active pharmaceutical ingredients (APIs), the mass contributed from over the counter (OTC) sales are often not included due to difficulty obtaining this data and topical formats are overlooked completely. This study presents a comprehensive approach, investigating the significance of OTC and topical applications as sources of API releases to wastewater, in addition to temporal and subnational variations in use in the UK. The study provides methods to obtain and make use of OTC sales data which can be applied widely. The calculated releases to wastewater compared well with influent concentrations measured at several UK wastewater treatment plants (WWTPs). Consistent overestimation was observed, attributed to a number of factors, including in-sewer removal. OTC sales were found to make up a large proportion of the mass of ibuprofen (76%) and diclofenac (35%) consumed and topical formats were also found to be vital, contributing disproportionately to wastewater loadings per unit mass of ibuprofen and diclofenac used (43% and 99% of the total mass released, respectively). Releases of the APIs investigated did not vary temporally, but regional variation was significant and where possible should be considered for the most accurate exposure assessment of pharmaceuticals.