Application of catecholamine metabolites as endogenous population biomarkers for wastewater-based epidemiology

Wastewater-based epidemiology studies use catchment populations to normalise chemical marker mass loads in 24-h composite wastewater samples. However, one of the biggest uncertainties within the field is the accuracy of the population used. A population marker in wastewater may significantly reduce the uncertainty. This study evaluated the catecholamine metabolites - homovanillic acid (HVA) and vanillylmandelic acid (VMA) - as potential population biomarkers. Influent wastewater 24-h composite samples were collected from 38 wastewater catchments from around Australia (representing ~33% of Australia's population), extracted and analysed by liquid chromatography tandem mass spectrometry. Measured mass loads were compared to population sizes determined by mapping catchment maps against high-resolution census data. Both biomarkers correlated with coefficient of determinations (r²) of 0.908 and 0.922 for HVA and VMA, respectively. From the regression analysis, a slope (i.e. the daily per-capita excretion) of 1.241 and 1.067 mg.day^-1.person^-1 was obtained for HVA and VMA, respectively. The mass load ratio between VMA:HVA were very similar to that reported in literature for urinary analysis among all catchments. Overall, this study provided further evidence that catecholamine metabolites are suitable candidates as population biomarkers for future studies.