Tempe has been collecting samples from its sewers for seven years, looking for traces of opioids flowing through the city’s pipes. Anyone who flushes a toilet contributes to the data.
The testing has detected emerging drug threats, giving authorities more than a week of early warning to prevent spikes in overdoses.
This approach to public health has spread but Tempe was the first to turn its wastewater into actionable intelligence about opioid abuse hotspots.
One key finding is that opioid use is spread across the city, dispelling stereotypes about “good and bad” neighborhoods – and guiding first responders to prepare for emergencies by deploying nalaxone more widely.
“We were finding not only with our EMS calls, but also with where the wastewater was indicating levels of metabolized opioids, it’s across the entire city,” said Wydale Holmes, director of Tempe’s Strategic Management and Innovation Office. “That helped level-set and start to destigmatize so that we were able to have these conversations.”
People are also reading…
The testing program works like a citywide health survey. Researchers analyze samples and then post the data on a public dashboard that shows opioid use in near-real time, at the neighborhood level.
Many U.S. cities also test wastewater for illicit drugs. But only a few besides Tempe post the data publicly, let alone in real time.
“They were very open to kind of thinking outside the box,” said Erin Driver, an environmental engineer at Arizona State University. Many other cities, she added, “were more afraid to see what’s in their wastewater.”
In Tempe, the number of fatal overdoses per year rose 25% between 2019 and 2023, when the city reported 90 overdose deaths.
Opioid-related EMS calls also increased from 330 in 2017 to 622 in 2024. But that represented progress, Holmes said, noting that the annual increase flattened after 2020 as the city got better at acting on the early warnings.
Wastewater testing that has been conducted in Tempe for seven years has detected emerging drug threats, giving authorities more than a week of early warning to prevent spikes in overdoses.
The initiative began in 2018 with a $35,000 city innovation grant. That year, there were 1,116 opioid deaths in Arizona. Maricopa County reports an average of three overdose deaths per day from fentanyl.
Tempe set a goal of eliminating opioid abuse in the city by 2027.
It quickly became apparent that the testing spotted patterns that hadn’t shown up in arrests or medical reports yet.
“The folks on the ground would say, ‘Hey, we’re seeing more activity in this location,’ so we tried to link that with what we were seeing in wastewater,” Driver said. “If we had a spike in activity, it made responders more aware – maybe we need to carry more Narcan.”
In 2019, the city held an Opioid Town Hall to share findings and reduce stigma, and launched the public online dashboard to inform prevention, treatment and community health strategies.
The program expanded to include COVID-19 monitoring during the pandemic that began in early 2020. Opioid testing was suspended for more than two years, resuming in November 2022.
Monitoring wastewater for opioids lets public health authorities and law enforcement detect drug threats before overdoses, arrests and drug seizures spike.
The opioid crisis nationwide persists, though it has abated somewhat. In Arizona, the annual death toll peaked at 2,015 in 2021, more than double the 2017 toll.
According to the state health department, on average four people died in Arizona every day from overdoses through Sept. 11 this year. The 1,116 deaths attributed to opioids is slightly below last year’s pace.
The city initially partnered with ASU’s Biodesign Institute and now works with Eurofins, a commercial testing lab for its BioIntel Wastewater Program.
The testing includes opioids such as fentanyl, heroin, oxycodone and codeine; COVID-19 and other respiratory viruses; and gastrointestinal viruses and flu strains.
Since summer 2024, the wastewater testing has also included xylazine, a veterinary tranquilizer that is often mixed with fentanyl, a powerful synthetic opioid that is fatal in even tiny amounts.
Also known as “tranq,” xylazine has been FDA-approved for animals since 1972 as a sedative and pain reliever. Though not an opioid, it can slow brain function and breathing and lower the heart rate and blood pressure.
Unlike fentanyl, xylazine does not respond to naloxone, the overdose treatment sold under the brand name Narcan. Because drug users often consume it unknowingly, community detection is especially helpful for emergency responders.
“If they respond to a call they think is related to opioids and the patient isn’t responding to Narcan, they then know, this could also be xylazine and we need to treat them a little differently,’” said Holmes. “It’s never absolute without toxicology, but it helps our teams anticipate and respond more effectively.”
In July 2024, Tempe’s testing program detected xylazine in five of six collection areas in the course of a single week.
Spotting the trends ensured that first responders were prepared with Narcan in the right places, and helped target prevention and education efforts, officials said.
“Wastewater data can tell you if a new drug has entered into your community. And it gives you an early warning of that drug compared to overdose data,” said Aparna Keshaviah, director of wastewater research at Mathematica, a policy research firm.
She co-authored a paper last year detailing an algorithm that used wastewater data from the District of Columbia, Maryland, Virginia and West Virginia to flag spikes in fentanyl, methamphetamine, cocaine and xylazine.
“We found that wastewater data could detect the entry of xylazine into a community at least one month before suspected overdoses involving xylazine appeared,” she said.
The algorithm was adopted from computer modeling developed during the COVID-19 pandemic, and it predicts overdose spikes with 71% to 100% accuracy – providing at least eight days to prepare.
The science is straightforward.
When people consume drugs, their bodies break them down into metabolites. Labs can determine how much was consumed by testing wastewater for both the parent compound and the metabolized version.
“Everything from your kitchen sink to your toilet to your tub – all of that goes into a sample,” Driver said.
To protect privacy, each collection zone includes at least 3,000 people. The program does not test sewage from individual homes or businesses. Areas that use septic systems aren’t covered because that waste doesn’t enter the municipal waste stream.
“It captures the health of a community,” even if individuals don’t see a doctor or seek treatment for an infectious disease, she said.
Since Tempe began testing its sewage for opioids, many other cities have seen similar benefits.
In Cary, N.C., with a population of 191,000, officials discovered that Narcan use was drastically outpacing the number of reported overdoses about 25 to 1. Using wastewater data, authorities began distributing Narcan more widely.
Opioid-related deaths plummeted, from 11 in 2017 to two by 2021.
In 2023, the National Institute on Drug Abuse issued a contract to Biobot Analytics, a biotechnology company specializing in wastewater-based epidemiology. The company now monitors 70 sites in 43 states, covering about 35 million Americans.
