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Testing the World’s Sewers for Illegal Drugs

If you want to know how people are getting “high” these days, you should look at what they dump in the sewer.  It sounds crazy, but increasingly substance abuse researchers across the globe are doing just that.

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According to a study published this week in the journal Addiction, “cocaine use is on the rise across Europe, methamphetamine is most prevalent in North America and Australasia, and the Netherlands has the highest rate of MDMA use.”

Researchers didn’t learn about these patterns by asking substance abusers to tell them – for years, the most common method of estimating types and levels of drug use.

Instead, they created a “comprehensive wastewater map” based on field testing of sewer samples collected in 120 cities in 37 countries worldwide.

The research team, led by Dr. Iria González-Mariño, a Spanish chemistry professor, reviewed wastewater samples over a 6-year period (2011-2017) and measured the residues from dozens of commonly-used illicit drugs.

It’s not the first time researchers have relied on such methods.  However, previous studies have focused on a particular city or event and have largely been snapshots of drug use levels and patterns at a particular moment in time.

The team began sampling wastewater in European cities in 2011 and expanded the survey to Australia, New Zealand, Colombia, Martinique, Canada, the US, South Korea, and Israel from 2014 to 2017.

To get a fair estimate, they also avoided sampling for drug residues during major festivals or other public events when drug use might be unusually high.

The highest level of drug use overall was found in cities such as Antwerp, Amsterdam, Zurich, London, and Barcelona, while cities in Greece, Portugal, Finland, Poland, and Sweden had the lowest levels of drug residue in their wastewater.

Wastewater testing is far from fool-proof.  Some drugs like marijuana are hard to test for accurately because of tetrahydrocannabinol (or THC) the drug’s psychoactive element, bonds too easily with wastewater particles.

Another problem is distinguishing legal from illicit use.  For example, Seattle tested high for methamphetamine use but the Spanish team acknowledged that legal drugs prescribed for attention-deficit/hyperactivity disorders could have boosted that finding.

González-Mariño says that her team’s methods for estimating THC levels correctly are improving.

“It is a tricky substance but I am confident our new methods will be good enough to include THC also in our next studies,” she noted in an interview with Vice.

Comparisons between the results from González-Mariño’s testing and more traditional survey research methods suggest that wastewater sampling is just as valid and reliable for estimating levels and patterns of illicit drug use.

However, wastewater testing has a distinct advantage, González-Mariño argues.

“The interesting thing of our methodology is that it provides data almost in real-time (samples are taken and analyzed within few days) so we get results ‘earlier’ than other indicators,” she noted.

For example, her team found a “spike” in benzoylecgonine, the metabolite compound in cocaine, in European cities from 2016 to 2017.  Apparently, cocaine purity had increased during that period, but her testing would have alerted authorities much earlier to the danger.

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Some countries like Australia have tested their wastewater for drug residues consistently for the past six years, with astonishingly precise results.

The most recent study produced by the nation’s Criminal Intelligence Division analyzed samples from 58 wastewater stations that encompass 56% of Australia’s population.

The commission found that cocaine and meth consumption had increased, while MDMA and heroin use was down.

However, overall illegal drug use, including marijuana use, was continuing to rise.

Some Australian territories and cities are especially noteworthy for increased opioid use while increased cocaine consumption predominates elsewhere.

Results from each wastewater station allow the Commission to conduct detailed spatial and temporal analysis, which assists in targeting drug enforcement and prevention resources.

In theory, the utility of wastewater testing is not limited to detecting and estimating illicit drug use.  With more refinement, the same methods might be used to test for alcohol, tobacco, caffeine, legal pharmaceutics or residues from pesticides and other hazardous materials.


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