In a way it seems so obvious: find out what kinds of things people are putting into their bodies by studying what comes out the other end. These do sound like muddy waters, but with some clever science researchers are able to draw some clear insights about the habits of different demographics of the population. And with their methods improving all the time, some see a bright future for this dark corner of science that involves real-time health monitoring, predicting disease outbreaks ahead of time and even tracking the rise of antibiotic resistance.

Just like a professional athletes urine sample can be checked for the presence of certain drugs, so too can ours. We dont all have an anti-doping official waiting at the bathroom door, but as our business makes its way into sewerage systems and pools with that of our neighbors, analysis of its chemical makeup can reveal the types of pharmaceuticals we have running through our bodies.

This field of science is known as wastewater-based epidemiology, and in the space of two decades has established itself as a valuable tool to track certain societal behaviors, but one with plenty more still to give.

In the early 2000s, scientists began to seriously explore the idea of tracking the use of illicit drugs by analyzing wastewater. This was inspired by the discovery of metabolites in lakes and rivers, which chemical analysis traced back to certain pharmaceutical compounds that had broken down in the waterways.

Some scientists saw no reason these same techniques couldnt be leveraged to track illicit drug use in the human population. The idea would be to sample wastewater at treatment plants and measure metabolites derived from illicit drugs, gathering non-incriminating drug usage data on the local population.

This is the first feasible approach to obtaining real-time data that truly reflects community-wide usage of drugs while concurrently assuring the inviolable confidentiality of every individual, wrote the EPAs Christian G. Daughton in the American Chemical Societys 2001 publication Pharmaceuticals and Care Products in the Environment. At the same time, this approach yields environmental data for a class of potential pollutants never before considered as such.

Daughton was onto something, it turns out. These days wastewater-based epidemiology has evolved to become a widely used tool by authorities all around the world. By sampling water from sewage treatment plants and measuring the chemical signals within it, scientists can make estimates on the quantity of drugs the community is using, and track the rise and fall of different drug types.

The SCORE network (Sewage analysis CORe group Europe) started out in 2010 as a collaboration between European scientists using wastewater analysis to track illicit drug use in different locations. At first, it involved 19 cities across the continent and by 2018 had expanded to cover 73 cities in 20 different European countries.

EMCDDA

This data is passed onto the European Monitoring Centre for Drugs and Drug Addiction, who work it into a publicly-available online tool that visualizes drug usage trends across the eight years of monitoring so far. By toggling different options, users can see hotspots for cocaine, amphetamine, methamphetamine and MDMA use across the continent, measured as milligrams consumed per 1,000 people each day.

And now other countries have gotten involved, helping to build a more complete picture of drug use around the world. An October paper published in the journal Addiction laid out the most recent data collected by the SCORE network, working with wastewater samples collected between 2011 and 2017, concerning more than 60 million people in 37 different countries.

It produced some interesting insights. For example, methamphetamine use was far more prevalent in North America and Australasia than in parts of Europe, though some hot spots emerged in Slovakia and the Czech Republic. Cocaine remains the drug of choice in Spanish, Italian, Swiss and French cities, while an overall upsurge was observed between 2011 and 2017. Ecstasy also grew in popularity in the cities sampled over the timeframe.

With this kind of generalized data on illicit drug consumption, the idea is that governments can better understand the role drugs play in the wellbeing of their communities. In turn, that can guide policy to curtail their harmful effects, whether that be through better use of police resources, more targeted awareness campaigns or the legalization of some substances that were seeing sweep through parts of the world.

Tying it all in with human behavior

The Australian government was an early adopter of wastewater-based epidemiology, starting out with a handful of testing sites in 2009 and now with a nationwide drug monitoring program in place. Through sewage samples, this initiative monitors the usage of 13 different substances, including nicotine, cannabis and opioid-based pain relievers, with local trends tracked through the help of chemistry researchers around the country. And some of them harbor grand ambitions for wastewater-based epidemiology.

Philip Choi is a PhD student using mass spectrometry and molecular biology to measure different aspects of population health through human waste. This extends beyond illicit drug use to include things like diet and the use of anti-depressants, making new connections between consumption habits and the lifestyles of the community.

The secret is to tie it all in with census data, which is exactly what Choi and his colleagues did the last time Australia conducted a nationwide census in 2016. The scientists had workers at treatment plants around the country freeze wastewater samples during the week of the census, and then mail them into Choi's lab at the University of Queensland for chemical analysis.

In searching these samples for certain biomarkers and comparing them to the census data, the team carried out the first ever study on the links between wastewater chemicals and social and economic measures of a population.

Prior to this study, some studies used wastewater-based epidemiology to study exposure to potentially harmful chemicals or pollutants such as pesticides, herbicides, flame retardants and so forth, Choi tells New Atlas. However, drug measurement studies made up the bulk of wastewater-based epidemiology studies. Additionally, previous studies measured what people are consuming. Our study is unique in that we show why people might consume different things.

And the results of the study, published in The Proceedings of the National Academy of Sciences in October, reveal some intriguing insights indeed. For example, the scientists found that the opioid-based pain reliever tramadol was used more heavily in areas where more people work as physical laborers. In areas populated by people with lower levels of education, they found higher use of anti-depressants and lower levels of dietary fiber. Some of these results were more surprising than others.

Before we analyzed our data, we expected socio-economically advantaged populations to have a better quality of diet, or take less drugs, and so forth, Choi explains. What was surprising, however, was that our data was able to show how specific aspects of socioeconomic advantage or disadvantage, such as having no home internet connection, lacking high school education, or having a high skilled occupation, were linked to diet or drug consumption. For example, we did not expect to find that lack of high school education was strongly linked to lower dietary fiber intake and higher consumption of amitriptyline, an antidepressant.

Higher caffeine and citrus consumption were other examples of habits tied to a strong socioeconomic status that revealed themselves through the wastewater samples. These new relationships that scientists are uncovering between human behavior and the chemicals in their sewage may prove highly valuable in building long-term pictures of population well-being, but could they also have an immediate impact, or even act as a warning sign of impending disaster?

As it stands, wastewater-based epidemiology is a laborious process that requires scientists to gather samples from different treatment plants and run chemical analyses to find out what's inside. But there could come a time when remote sensors built into treatment plants do most of the heavy lifting, and in much more expedient fashion.

"Some wastewater-treatment plants are already using inline sensors to measure specific chemicals in wastewater, such as online continuous monitoring of ammonium," Dr Jake O'Brien, a member of Choi's research team, explains. "There has been progress on developing more sophisticated biosensors for use in wastewater. Biosensors are small devices with a biological receptor, like DNA, an antibody, or a protein, that generates a signal in the presence of an analytical target, or analyte. They are already used for detection of disease biomarkers for both healthcare and environmental monitoring."

O'Brien points to sensor research being carried out at the UK's Cranfield University as an example of the exciting progress being made. Under the guidance of Dr Zhugen Yang, a research group at the university's Water Science Institute brings together cutting-edge biomedical and chemistry techniques to build next-generation sensors that connect wastewater with environmental science and human well-being. Yang also sees huge potential in using these techniques to offer a complete and immediate picture of population health.

"Wastewater-based epidemiology is very powerful to monitor the health at the community level," he tells us. "Compared to conventional analytical tools, sensors can provide rapid response times, ultra-sensitive detection of biomolecules, and the potential to be miniaturized for portable assays requiring minimal sample processing."

These tiny sensors Yang and his team are developing could be used to track pathogens in sewage that reveal outbreaks of certain diseases earlier on. Furthermore, he says they could also be tuned to track indicators of general health risks like diabetes, high blood pressure, sexually transmitted infections and even obesity.

"A recent report demonstrated that the level of an American citys obesity could be predicted by analyzing the bacterial community structure found in sewage," he explains.

Implementing these kinds of advanced sensors on a scale large enough to track population health sounds like a huge undertaking, and an expensive one. But Yang explains that the costs are something his team is already considering, and mightn't be as prohibitive as you'd think.

"Actually, generally those sensors are not so expensive, and we can really reduce the cost of sensors by using cheap material," he says. "For example, recently I have developed a paper-origami device, using filter paper as material to build up hydrophobic and hydrophilic channel to manipulate the liquid rather than using a pump. So I dont think the cost of sensors will be a main limitation for this kind of application."

The rise of antibiotic resistance bacteria, also known as superbugs, is a growing concern among scientists with many fearful they could return us to the dark ages of medicine and kill tens of millions a year by midway through the century. Wastewater-based epidemiology could emerge as a valuable tool in tracking their evolution, and the communities that are most at risk.

"Our recent work also demonstrated a low-cost later flow assay, which can be performed at the site of sample collection, with minimal user intervention, yielding results within 45 minutes and providing a method to monitor public health from wastewater," says Yang. "This can also be used for the tracking of antibiotic-resistant genes, with my research group currently working on the development for these kinds of sensors. The sensor will enable rapid monitoring of antibiotics and antibiotic resistant genes in wastewater."

There are still technical hurdles involved in building real-time sewage monitors to track human health, however. Yang says there are currently a handful of sensors that can perform real-time monitoring of chemical elements, but building versions to identify the right biological signals in real-time presents some unique challenges.

"As most current state-of-the-art sensor technologies for chemical and biological targets are mostly based on the bio-recognition element, the bio-receptor may become too saturated for a long-term detection during deployment, especially for the detection of the complex wastewater matrix," he says. "This is our opportunity to improve those sensors for wastewater-based epidemiology, which ultimately can be deployed for the real-time monitoring."

If these kinds of problems can be overcome, we could see humankind's excrement become an early warning system for some of its biggest health concerns. And then it might no longer be seen as waste at all.

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The science of sewage: What your wastewater could reveal about you - New Atlas