Wastewater-based epidemiology as a method to explore spatial, temporal, and sociodemographic patterns of drug use: A New Zealand case study

Abstract

Wastewater-based epidemiology (WWBE) is a relatively young field of research which uses advances in analytical chemistry to investigate community-level drug use through the analysis of municipal wastewater. Being a young discipline, the WWBE literature has focussed on describing and refining analytical techniques. There are areas of research still to explore, particularly practical applications such as how drug use patterns vary between urban and rural communities, and whether these patterns reflect sociodemographics. This thesis uses WWBE to investigate drug use patterns in New Zealand. Daily composite wastewater samples were collected at seven wastewater treatment plants of varying size and location during census week in March 2018. The aim was to best capture the sociodemographics of each catchment for comparison with drug use. Samples were analysed for methamphetamine, cocaine, MDMA, nicotine, alcohol and morphine via LC-MS/MS using standard methods. Drug use was back-calculated based on detailed catchment mapping using GIS maps of the reticulated pipe network for each site and the best available sociodemographic data, which did not happen to be census week information. Drug consumption rates were compared between sites, throughout the week and correlated with sociodemographic measures of age, ethnicity and (dis)advantage. Cocaine and MDMA consumption were higher in cities, whereas methamphetamine use was higher in rural locations. However, the considerably high rates of methamphetamine use at Te Maunga (Bay of Plenty’s urban site) showed that methamphetamine use is not particular to rural communities. Cocaine, MDMA, and alcohol consumption were higher on weekends, and this was more pronounced for cities. Conversely, nicotine and morphine were consumed consistently throughout the week. Weekly patterns of methamphetamine consumption were different across sites. Methamphetamine and nicotine were positively correlated with metrices of disadvantage, whereas cocaine and MDMA were positively correlated with metrices of social advantage. These findings demonstrate that drug use patterns varied across communities, and that these patterns are attributable to supply dynamics, social preferences and sociodemographic characteristics, namely community-level measures of disadvantage. This thesis ends with a frank and open discussion about the accuracy of WWBE to draw implications for how WWBE data is interpreted and applied in drug policy.