Cities are rich with information. Look closely, be it through street cameras, our phone GPS, or our grocery bills, and you can see patterns in how we live. But new research from the University of Queensland and the Norwegian Institute for Water Research has found a rich source of information beneath the surface of the city—specifically in the sewers.
Their findings show that our wastewater can reveal a lot about the way we live, revealing details about our diets, drug use, and even our propensity for artificial sweeteners. Combined with demographic data, our waste can reveal large-scale insights about income, health, and more. In many ways, underground waste is a direct reflection of life above.
The paper, published in the Proceedings of the National Academy of Sciences, analyzed the contents from 22 different wastewater treatment plants (WWTPs), spread across six states and territories inside Australia. That represented a huge sample size of roughly 21% of the entire population of Australia. Using some pretty clever methodologies, the scientists actually lined up their localized waste samples with the exact timing and location of the 2016 Australian census.
In other words, while the government was collecting demographic data from populations across the country, the researchers were freezing and analyzing their poop.
They were ultimately able to measure 42 specific biomarkers in our waste that could signal highly specific information, like our intake of fiber and citrus, or use of extremely particular painkillers.
Much of what they found was a link between income level and both diet and drug use. People in wealthy areas appeared to eat healthier and use fewer opioids, illicit drugs, and tobacco products than people in areas with lower incomes. Surprisingly, income correlated with more alcohol and coffee consumption. Regarding coffee, researchers point to the intelligentsia institution that coffee has become, in which this choice of beverage is actually a statement about one’s self. You could easily say the same thing about wine, whiskey, or craft beer, too—all of which are tasty, and culturally prized delivery systems for a chemically identical ethanol buzz.
One of the most surprising findings had to do with antidepressants. Like other drugs, people with more economic advantages used fewer antidepressants. (As the researchers put it: “We considered antidepressants as a proxy for psychological distress.”) That was all expected. However, the types of antidepressants people took correlated with lifestyles. Laborers took more desvenlafaxine. People who lived alone or were divorced took more citalopram. Amitriptyline was associated with education and higher degrees. Exactly why is unclear, but looking into the medical description for desvenlafaxine, you see it’s an antidepressant that also treats painful physical symptoms. It seems reasonable that laborers are in more pain, and so their doctors prescribe a double-duty antidepressant painkiller.
In any case, the individual discoveries of the study are really intended to prove a larger point: that our sewage clearly has the capacity to reveal an incredible amount about us on the urban scale. It literally conveys the substances people ingest in certain areas, and by proxy the greater health of socioeconomic groups living inside a city. Our wastewater is a portrait of our stressors, our indulgences, and our good and bad habits. Perhaps it’s worth cities taking a more continuous look.