The Secrets in Our Sewage – Part II

You’re reading Part II in a 5-part series about sewage science. Catch up on Part I before diving into this one.

Scientists have long monitored sewage for harmful contaminants with the goal of improving wastewater treatment practices. But no one had ever proposed studying sewage to better understand the people that contribute to it.

That is, not until former EPA scientist Christian Daughton. In the 1990s, the EPA focused solely on identifying “priority pollutants” like pesticides, heavy metals, and solvents in wastewater. But other substances—like drugs, both legal and illegal—could have environmental impacts, too, if they leaked from sewage. In 1999, Daughton coauthored a paper that considered how pharmaceuticals in sewage could be contaminants in the environment. Soon after, he published a book on the topic—and offered a ground-breaking proposal. Rather than studying how pharmaceuticals in sewage impacted the environment, why not see what they can tell us about community-wide drug use?

“That was the very beginning of this idea of monitoring things in sewage, not as contaminants, but as markers for human activity, human behavior, human action,” Daughton said.  

Some of his peers doubted the idea. “Several of the scientists involved with the review said, ‘Why are you doing this?’” Daughton recalled. In their view, it had nothing to do with the environment and the mission of the EPA.

But other scientists saw the value of studying sewage as a proxy for human activities. The first demonstration was in 2005, when a team led by Ettore Zuccato measured cocaine in untreated wastewater in Italy. This proof-of-concept experiment opened the floodgates: Since then, researchers have published a flurry of studies using wastewater to track consumption and use of caffeine, alcohol, tobacco, antidepressants, antibiotics, asthma medications, antihistamines, and more.  

Sewage has also been crucial to studying the opioid crisis. When you take a painkiller, your body metabolizes it, breaking it down into different products as it moves through the digestive system. The metabolites, which are in a different form than the original “parent” compound in the drug, then get secreted through feces or urine. When you flush the toilet, the waste travels through networks of pipes to sewage treatment plants.

Fahad Ahmed, a graduate student at the University of Queensland in Brisbane, Australia, analyzes the raw, untreated sewage by capturing the metabolites onto a special type of column and using a device called a mass spectrometer to obtain their concentrations.

Ahmed then tries to estimate what he calls the “pain burden” of a community. But to get from the concentration of a metabolite to the amount of painkiller consumed per day—the way such figures are typically reported—he needs to know a lot more information. For instance, how the painkiller is processed in the body, how much of the metabolite is excreted, how fast the sewage flows, and the size of the “catchment,” or the population that serves a given treatment plant, could all influence calculations. Ahmed makes reasonable estimates to translate the concentration of a metabolite in the sample of sewage into a pain index. Armed with this knowledge, Ahmed hopes that health officials can develop strategies for alleviating the burden of pain while combating opioid addiction. In the U.S., researchers including those at the startup Biobot and the Human Health Observatory at ASU have partnered with cities to use their wastewater data to assess the effectiveness of drug take-back initiatives.

Such wastewater surveillance programs allow governments to measure the effects of drug policy, identify trends in use, and flag harmful new drugs that enter the market. Since 2011, Sewage Analysis Core Group Europe, or SCORE, has tested sewage in cities across the continent for the presence of cocaine, MDMA, amphetamine, and methamphetamine. A similar monitoring program was started in Australia through the Queensland Alliance for Environmental Health Sciences. In Canada, the national statistical agency Statistics Canada started monitoring marijuana use in six cities in April of 2018.

Dan Burgard, professor of chemistry at the University of Puget Sound, has been a member of SCORE since 2015. Burgard became interested in wastewater analysis after his students told him about the prevalence of “study drugs” like Adderall on campus. Wanting to better understand patterns of use and abuse, he collected samples from a manhole capturing the waste flowing in from four dorms. Unsurprisingly, Burgard found a clear increase in the use of study drugs during periods of high stress, like midterms and finals. During one particular time period—finals week of spring semester—the levels of Adderall were eight times higher than during the first week of school, Burgard said.