Analyzing Wastewater Samples Collected during Census To Determine the Correction Factors of Drugs for Wastewater-Based Epidemiology: The Case of Codeine and Methadone

The correction factor (CF) is a critical parameter for back-estimating the consumption of a drug via wastewater-based epidemiology (WBE). The CF is usually the excretion factor (EF) of the drug or metabolite (the fraction of drug excreted after consumption and the molecular mass ratio of parent drug/metabolite) traditionally determined by human pharmacokinetic studies. An alternative approach to derive CFs is to compare the consumption data with the loads measured by WBE in representative wastewater samples. For this purpose, during the 2016 Australian Census week, more than 500 wastewater samples were collected from 83 wastewater treatment plants across Australia (covering >60% of the Australian population) and analyzed for codeine, methadone, and methadone metabolite, EDDP. National sales data for codeine and methadone to local pharmacies were obtained to estimate the CFs for the three biomarkers. The CFs estimated for codeine and EDDP in this study, 29% (95% CI = 28%–30%) and 50% (95% CI = 49%–52%), re...