Mirror, mirror on the wall - Wastewater as a source of health data
The use of water-based sanitation systems turns untreated wastewater into a mirror that incorruptibly reflects the life of communities. In theory, any indicator of human health and various markers for human diseases can be studied with the help of wastewater.

Wastewater research offers an exceptionally extensive and almost real-time dataset for assessing changes in the lifestyle and health of populations.

“Wastewater research enables the identification of a wide range of pathogenic microbes in the population using the sewer network. It enables also the monitoring of, for example, consumer chemicals in everyday use,” says Tarja Pitkänen, Associate Professor of Environmental Health at the University of Helsinki. Pitkänen also works as a chief specialist at the Finnish Institute for Health and Welfare, investigating water-borne pathogenic microbes.

Untreated wastewater contains all the microbes that cause infectious diseases and which are secreted into lavatory and washing water by the local population. Among other pathogens, wastewater has been used to monitor the occurrence of poliovirus and the SARS-CoV-2 virus, which causes COVID-19.

“The special value of wastewater data is that although not all carriers of infectious diseases necessarily develop a symptomatic infection, they can still infect other people. Wastewater contains the microbes secreted by such asymptomatic carriers as well,” Pitkänen explains.

In fact, the wastewater monitoring carried out during the coronavirus pandemic has increased interest in the opportunities offered by the technique.

Lifestyles and consumption habits under the loupe

Markers for non-communicable disease, such as diabetes, cancer or allergy, can also be measured from wastewater. It is also possible to detect in wastewater gut microflora linked to obesity or markers for oxidative stress, which reflects a state of stress in the body.

Drug use also leaves a mark in wastewater. Through wastewater monitoring, it is possible to obtain consumption data on the use of pharmaceutical agents or different chemicals that is more accurate than sales statistics.

“The significance of wastewater monitoring has been understood as a monitoring tool for bacteria that have developed antibiotic resistance,” says Pitkänen.

“Antibiotic resistance is spreading slowly, but apparently inevitably. Wastewater monitoring can help obtain important information on this silent pandemic and its regional differences,” she adds.

Real-time data in support of decision-making

Monitoring illegal drug use has been among the most significant applications of wastewater epidemiology both in Finland and abroad. The national wastewater monitoring initiated in 2012 by the Finnish Institute for Health and Welfare for assessing the scope of illicit drug use is one of the most comprehensive in the world in proportion to the population.

“Many changes in drug use have been first identified or verified with the help of wastewater epidemiology,” says Teemu Gunnar, Head of the Forensic Chemistry unit of the Finnish Institute for Health and Welfare. Gunnar has overseen drug-related wastewater monitoring in Finland from the beginning of its implementation.

According to Gunnar, an up-to-date overview of drug use is important for authorities and substance abuse professionals, as well as for decision-makers to ensure that decisions and measures are based on the most accurate and current information possible.

“Knowing the drug situation is key when planning measures, for example, to prevent substance abuse problems,” Gunnar says.

“The data on drug use gained through population-level wastewater epidemiology strongly correlate with the prevalence of at least certain societal side effects of drug use, such as driving under the influence of narcotic substances,” he explains.

A brighter future for wastewater monitoring

According to the researchers, data provided by wastewater could be used even more diversely in communities: the water could serve as a warning system for identifying emerging health threats or regional differences.

“The utility value of wastewater monitoring is at its highest when monitoring can be carried out using globally harmonised methods at regular intervals and in a nationally comprehensive manner,” Tarja Pitkänen says.

She points out that the appropriate allocation of limited resources requires planning and prioritisation.

“Solutions will be found by utilising scholarly research and the international networks of wastewater epidemiologists,” Pitkänen states.

This text is an edited version of an article published in a Think Corner paperback entitled Terveempi maailma — Kuinka vastaamme globaaleihin terveysuhkiin? (‘A healthier world – How to respond to global health threats’).