A total number of 58 parent AAs and 26 metabolites were tested in two contrasting catchments (>100K inhabitants in the city of Bath and <20K inhabitants in the town Keynsham) over 13 months. A diverse range of AAs (17 parent AAs and 8 metabolites) were quantified in the wastewater of both communities. AA average loads were, as expected, higher in Bath than in Keynsham (on average 83 ± 24% higher) as AA loads are population size driven. Full breakdowns of loads of all studied AAs can be found in Sims et al. . Seasonal variability of a handful of AAs across different classes was also observed, including MTZ, SLZ, LEX, CIP, and CLR reporting higher loads in winter versus summer. Other AAs reported low temporal variability during the studied period, including the sulphonamides SMX and SPY. A common observation was that the total prescribed AA mass in winter was higher than in summer -particularly for the macrolide, penicillins and cephalosporin classes .