Wastewater-based epidemiology: making a pipe dream reality

TEN years ago, the idea of estimating illicit drug use in Australia by measuring metabolites in wastewater was just that: an idea. But in 2019, the National Wastewater Analysis Drug Monitoring Program is in its third year of providing scientific evidence to inform drugs policy in Australia.

How does wastewater-based epidemiology work?

Wastewater-based epidemiology (WBE) quantifies chemical and biological markers in wastewater. Systematic samples are collected at the inlet of wastewater treatment plants (WWTPs) to ensure that they are representative of the communities from which they originated. Australia is unique in that a large percentage of the population is covered by a small number of WWTPs – the largest five plants cover over 30% of the population, and the largest 20 cover over 50%. In most states, two to five WWTPs capture the wastewater from more than half the population.

A wastewater sample is a community urine sample. Interpretation of the sample requires information on the total flow of wastewater for that day in the catchment, the size of the population, and knowledge of the stability of chemicals within the sewers. When the data are population-normalised, spatial and temporal comparisons can be made. For example, WBE has been used to compare drug use for a week each year in over 70 cities in Europe and to identify which drugs are used where and in what quantities per person. In Australia, WBE has also identified an almost fivefold increase in methamphetamine consumption between 2009 and 2015 in southeast Queensland and Adelaide.

To date, WBE in Australia has been used to estimate the population’s consumption of alcohol, tobacco, illicit drugs, foods, pharmaceuticals, environmental chemicals and response to allergies. Research conducted elsewhere has shown that WBE can potentially measure markers of population health such as antimicrobial resistance, blood glucose and oxidative stress.

WBE data complement health surveys to provide a more complete picture of population health. For example, the most recent Australian Burden of Disease Study identifies tobacco use as the largest individual risk factor contributing to the burden of disease in Australia. Between 2009 and 2016, the Australian Government spent over $135 million on antismoking campaigns’ Strategies that were implemented during this time included plain packaging of cigarettes, and larger graphic health warnings on the packs, the widening of smoking bans, point-of-sale display bans, and substantial increases in tobacco taxation.

WBE in an Australian city found a 25% reduction in the average number of cigarette equivalents between 2010 and 2017. WBE has also identified communities where tobacco consumption is well above the national average and warrants further intervention.

Public health monitoring and evaluation ideally needs to rapidly identify major risks to public health and wellbeing. The unprecedented speed of urbanisation that we are experiencing globally and within Australia poses substantial risks to the resilience of cities. According to the 2016 Australian census, more than two-thirds of Australians live in a capital city, an increase of 10.5% since the 2011 census. A major strength of WBE is that public health data on cities can be collected in near-real-time and at modest cost, allowing for the possibilities of early identification of public health risks and evaluation of the success of policy responses.

WBE has the additional advantage that samples contain both endogenous markers of population health (eg, inflammation) and markers of human chemical and biological exposures. When combined with census data on the wastewater treatment catchment area, important demographics and socio-economic relationships may be identified – for example, is analgesic use higher in areas with older populations? or is binge drinking more likely to occur in younger populations? This may provide valuable information to predict the future health of Australia’s growing and ageing populations and the demands this may place on the health care system.

WBE is not limited to the analysis of sewage influent; it can also be used to monitor the per capita release of chemicals, including hazardous chemicals, into the environment. Some examples include antibiotics and other chemicals that may cause antibiotic resistance, chemicals that can affect reproductive function, and chemicals used in industry. The demand for data on release of these chemicals is growing as urbanisation and climate change increases the need for wastewater recycling.

Another important source of data is the solids produced during the wastewater treatment process, termed “biosolids”. These are rich in nutrients and organic matter and may contain chemicals that affect human, plant and animal health, such as flame retardants, pesticides, trace metals and microplastics. In Australia, biosolids are used in both agriculture and horticulture, with the result that toxicants that are removed from wastewater effluent can potentially re-enter the human food chain.

Long term, coordinated WWTP sampling can uniquely measure a wide range of human and environmental health exposures in the populations served by the plant. Wastewater influent, effluent and biosolids are good places to look for undiscovered population exposure sources. WBE may thereby form a key part of a national early warning system for emerging environmental hazards.

It is time to develop a national framework for WBE which, in addition to monitoring alcohol, tobacco and illicit drug use, will also collect baseline data on the chemicals that the Australian population consumes or is exposed to and those that are released into the environment. This information will enable policy makers to monitor the impact of community public health interventions. This will require secure funding for WWTP staff to collect and archive systematic samples of wastewater, and trained chemists, toxicologists and epidemiologists to conduct timely analyses and interpret the data.

A national WBE program would add substantial value to the National Health Survey by providing data on human exposures that cannot be measured accurately by self-report. Adequately resourcing a national WBE monitoring program in time for the next national census would enable Australia to realise the promise of WBE in providing cost-effective, high resolution and timely assessments of the health of Australians into the future.

Dr Jake O’Brien is a Research Fellow at the Queensland Alliance for Environmental Health Sciences, University of Queensland.

Associate Professor Coral Gartner is an Associate Professor at the School of Public Health and Theme Leader at the Queensland Alliance for Environmental Health Sciences, University of Queensland

Professor Kevin Thomas is Director of the Queensland Alliance for Environmental Health Sciences, University of Queensland.

Professor Wayne Hall is a Professor at the Centre for Youth Substance Abuse Research (CYSAR) at The University of Queensland and a Visiting Professor at the National Addiction Centre, Kings College London.

The statements or opinions expressed in this article reflect the views of the authors and do not represent the official policy of the AMA, the MJA or InSight+ unless so stated.