Showcasing the potential of wastewater-based epidemiology to track pharmaceuticals consumption in cities: Comparison against prescription data collected at fine spatial resolution.

While the extent of pharmaceutical consumption within a society/community is of high relevance to its health, economy and general wellbeing, this data is often not readily available. Herein, we strengthen a wastewater-based epidemiology (WBE) approach as a way to track the consumption of pharmaceuticals within the sampled community. This method is less laborious than established questionnaire or databases approaches and allows a higher temporal and spatial resolution. The WBE approach was conducted by sampling influent wastewater from two wastewater treatment plants of different size. A total of 39 targeted compounds were quantified by liquid chromatography coupled with tandem mass spectrometry. The number of prescriptions and the defined daily doses for each prescription was obtained from the reference database of The Catalan Health System to validate the wastewater-based approach. The wastewater sampling and the data inquiry were both executed during the same period (October 2019) and standardised for comparison to treatments per 1,000 inhabitants per day. The back-calculation parameters were improved from previous studies by including the faecal excretion rate of the pharmaceuticals. For prescription only pharmaceuticals, where prescription numbers are expected to be a good estimate of consumption, our WBE approach agreed with 27 out of 32 (<0.7 order of magnitude). Common over-the-counter pharmaceuticals such as acetaminophen, ibuprofen and naproxen showed much higher values for treatments per day per 1,000 inhabitant in wastewater than prescribed, reflecting the usefulness of WBE in obtaining an estimate of the total consumption i.e. with and without a prescription.