Wastewater Surveillance

The coronavirus could turn sewage surveillance into a mainstream public health practice - Emily Anthes

Wastewater Surveillance

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I have made what you excrete my daily business for almost two decades now. That means retrieving, from municipal sewers, wastewater that was created by thousands of people, rushing it to the laboratory, and analyzing it for toxic chemicals, human pathogens and biomarkers of harmful exposures. We have been fighting both the opioid epidemic and COVID-19, creating in the process the world’s first open-access electronic dashboards displaying opioid and coronavirus abundance at the neighborhood level to help inform public health actions.

The results can be counted in hundreds of offhand jokes, thousands of news stories, and millions of lives improved. I even went to Capitol Hill in Washington DC to brief members of Congress on the chemistry and biology flowing in the sewers below our feet. There have been real-world results, too: Information garnered from the municipal sewers helped to bring about the 2017 federal ban of risky antimicrobial chemicals from more than 2,000 personal care products sold in the U.S.

But there always are those questions we need to ask, again and again: What information is OK to collect? How many people’s human waste needs to be mixed to make the data we collect anonymous? Who owns the data, and who deserves to learn about what it says? If a changing climate or global tourism bring new pathogens into your city and neighborhood, we work to be the first to tell you.

Powerful tools are neither good nor bad; it just depends how they are applied. Wastewater-based epidemiology and other health monitoring tools are no exception. They are, figuratively speaking, a hammer that can be swung to extinguish a deadly microbial threat or to stigmatize a vulnerable sub-population. We scientists receive little to no formal training on how to make responsible decisions concerning the powerful tools we yield. Stories like Laura Walter’s fiction are an important impetus for never stopping to ask whether what we do is right. The decision process resembles the waste we analyze: it’s murky and messy, and it meanders as a function of purpose, place and people.

How far have we evolved in the monitoring of our waste and will the path of discovery take us where Laura Maylene Walter’s “Beauty Surge” leads? Analyzing our excreta to diagnose health is by no means new. In ancient Egypt and Rome, healers sniffed the bodily fluids of the diseased to diagnose and treat ailments. Several millennia later, scientists detected the polio virus in wastewater in Israel and rushed in to vaccinate the vulnerable to snuff out a still invisible epidemic that otherwise may have claimed thousands of lives.

The one-two punch of first using a wastewater radar to detect community health threats and then mounting a public health intervention, such as a vaccination program, has saved lives and today protects millions of people. This is what the COVID-19 pandemic has taught us: Population health monitoring works. It is cheap. It is feasible and practical. And it is equitable, reaching virtually everyone irrespective of wealth, health insurance, immigration status or political leanings.

Today, more people than ever before benefit from wastewater monitoring. My nonprofit project, OneWaterOneHealth of the Arizona State University Foundation, has brought COVID-19 wastewater monitoring to states across the nation, aiding minorities in underserved geographic regions and helping to control COVID-19 clusters in Tribal and Hispanic communities. (Disclosure: ASU is a partner with Slate and New America in Future Tense.) This pro bono work yields actionable data that save lives. But paying to monitor community health threats in wastewater makes good business sense, too. Customers of AquaVitas LLC, a commercial venture that was spun out of my ASU research laboratory, is commercializing wastewater sampling devices, detection methods, and data analysis and visualization services; the company has seen explosive growth in interest from municipalities to Fortune 500 companies, eager to protect their residents and workforce at a small cost, thereby realizing a high return on investment. Most recently, AquaVitas performed the first phase of the largest wastewater-based epidemiological study to track COVID-19 for the U.S. government, reaching some 40 million people in more than 100 U.S. cities. Next up, genetic sequencing of the coronavirus genetic information to learn from where and how variants have spred across the U.S.

Indeed, wastewater monitoring thrives on scale. The more people are represented in the composited excreta, the cheaper the technology gets and the more powerful public health protection becomes. For biomarkers that decay quickly during travel in the sewer pipe (like SARS-CoV-2, the virus that causes COVID), better data are obtained when reducing the area surveyed to capture the virus signal before it disappears. A signal that is impossible to observe at the city scale becomes detectable and actionable, when the monitoring area is reduced to a few thousand people. But there is a tradeoff between spatial resolution and practicality as well as economy. Sampling sewage city block by city block quickly becomes cost prohibitive and impractical. (Step aside please, I’d like to access that sewer maintenance hole you’re standing on.) Monitoring large buildings with hundreds of occupants, such as schools and university dorms, still is cost-effective and helpful in controlling COVID-19. But if you are worried about the privacy of your own excrement, I have good news: Currently, venturing beyond this scale to monitor individual apartments and private restrooms is unrealistic, impractical, and cost-prohibitive, meaning for now “Beauty Surge” can be understood as a dystopian fantasy.

The legal and ethical framework of wastewater monitoring is still in its infancy. Defining where population monitoring ends and surveillance of individuals begins is important but surprisingly difficult. For common biomarkers excreted by just about every individual, such as caffeine and stress hormones, mingling of the excreta of a few individuals is sufficient to make tracing back the signal to an individual utterly impossible. But beware, if you were the only user of a medical imaging contrast agents or if someone had poisoned you with a radioactive chemical, your mobility potentially could be traced by wastewater monitoring from one neighborhood or city to another.

And what about BeautyAid and Laura Walter’s toilet-to-tap scenario that sends chemicals into an endless loop? Is such cycling of chemicals from drinking water to wastewater and back to drinking water really possible? Unfortunately, yes! This is indeed true and not only for polyhalogenated chemistries of carpet protectants and textiles. Think of this next time when you hold between your thumb and index finger a little pink sachet of powder to sweeten your coffee or tea. The artificial sweetener therein, sucralose, does not expand your waistline, because neither you nor the bacteria in your gut can degrade this triply chlorinated sugar. Unfortunately, neither can the microbes in the wastewater treatment facility, thereby returning the artificial sweetener in reclaimed water right back into your drinking water supply. (My students and I have researched sucralose and once calculated what level of consumption it would take to turn our Arizona freshwater into sweetwater. The answer: a lot.)

So where do we cross over from scientific reality to impossible fiction? The monitoring described in “Beauty Surge” at present would be impractical in specificity, sensitivity, scale, and economy. But technologies get better and cheaper all the time. Thus, it makes good sense to think about the futures that may await us and which ones we should work toward living out.

From COVID-19 we learned that wastewater monitoring is too potent a public health tool to not be used. While it took a global pandemic to herald it in, the dream of diagnosing entire cities, as postulated in my pre-pandemic 2020 book Environment, has quickly become a reality and is practiced today in hundreds of municipalities around the world. And for good reason. Used responsibly and judiciously, this health threat radar protects populations including you and your loved ones; and while you remain anonymous and untraceable, the data collected are being used to extend your life expectancy and improve your quality of life.

So keep on flushing in the free world but also watch out what you put into your body because, like it or not, some of the chemistries we produce, including unsustainable plastics, have a tendency to come back to and into us, again and again.

Source: Rolf Halden, Are You Entitled to Privacy Over Your Pee and Poop?, Slate, August 28, 2021.

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Last Updated : Monday, December 6, 2021