Drugs in wastewater can reveal usage trends

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  • Published: Jan 18, 2007
  • Author: Steve Down
  • Channels: Base Peak
thumbnail image: Drugs in wastewater can reveal usage trends

Illicit drug use remains an acute problem throughout the world. The latest World Drug Report published by the United Nations Office on Drugs and Crime (UNODC) estimates that about 5% of the global population aged 15-64 used illicit drugs at least once during 2006. That's around 200 million people. The greatest misuse involves cannabis (162m people), followed by amphetamines (35m), cocaine (13m), heroin (11m) and ecstasy (10m). However, these figures are clearly broad approximations.

The report states "The paucity of the data on which the annual prevalence estimates are based does not allow for the identification of clear global trends in the short term." The UNODC relies on the perception of national experts to estimate drug usage trends in their own countries which, it admits, is an imperfect process, based on many estimates and assumptions.

It was these uncertainties that stimulated Italian researchers in 2005 to try another way of estimating drug use, by measuring the levels of drugs in river water. Ettore Zucatto and colleagues from the Mario Negri Institute for Pharmacological Research in Milan, with co-researchers from the University of Insubria in Varese measured the levels of cocaine and its principal metabolite, benzoylecgonine, in the River Po. They discovered that the river carries about 4 kg of cocaine per day, equivalent to 27 doses per 1000 young people.

The official figures suggested that there were 15,000 cocaine-use events per month but the experimental evidence suggested that the real usage was about 40,000 doses a day. The authorities appeared to be seriously underestimating cocaine use in the Po river basin.

Now, the same team has extended the concept to a whole series of illicit drugs and their metabolites, including amphetamines, cannabinoids and morphine, as well as methadone, the heroin substitute. They collected samples from the influent and effluent flows of two wastewater treatment plants (WWTPs) that were fed primarily with domestic wastewater. The first WWTP was at Milan-Nosedo and served a population of about 1.25m people, with a flow rate of 380,000 m3/day. The second plant was at Lugano, Switzerland, serving about 120,000 people with a mean flow rate of 60,000 m3/day.

The samples were spiked with deuterium-labelled internal standards of the analytes and cleaned up by mixed-mode solid-phase extraction on reversed-phase/cation exchange phases. The extracts were analysed by LC/MS/MS with either positive- or negative-mode electrospray ionisation in multiple reaction monitoring mode, two product ions being monitored for each precursor ion.

The recoveries were 67-119%, with only the tetrahydrocannabinol metabolites giving poorer values. The variabilities were less than 10% for untreated wastewater and less than 5% for treated wastewater. The quantification limits (LOQ) were relatively low at less than 2 ng/L for influents, except for morphine and 6-acetylmorphine (4 and 5 ng/L) and amphetamines (3.7-8.7 ng/L). The corresponding values for effluents were less than 1 ng/mL, except for morphine and 6-acetylmorphine (3 ng/L) and amphetamines (1.0-2.8 ng/mL).

The majority of the drugs and their metabolites were found in the WWTP influents of both plants, cocaine and its metabolites being the most abundant in both cases. Benzoylecgonine was the most abundant analyte found, at 1132 and 547 ng/L, respectively, in Milan and Lugano. Three other cocaine metabolites were detected at lower amounts (4-36.6 ng/L). Morphine levels were also relatively high at 83 and 204 ng/L, respectively.

The Italian WWTP removed cocaine and its metabolites to below the LOQ but the Swiss plant did not, leaving about 18% of benzoylecgonine (100 ng/L) and 5% of cocaine (10 ng/L) in the effluent. Other analytes which were treated inadequately by the process included methadone and the amphetamine MDMA, for which 72-78% and 30-37.5%, respectively, remained in the water after treatment.

Overall, 16 illicit drugs and their metabolites were detected in the wastewater, confirming that the parent drugs should be considered ubiquitous environmental contaminants. The presence of some in treated effluents is a cause for concern.

Although they did not do so in this case, the researchers claim that measurement of the drugs and metabolites in WWTP influents could be used as a measure of drug abuse in the catchment areas, in a similar way to their previous work on cocaine. General trends and changing drug habits could be monitored regularly in a way which guarantees user anonymity and the data can be used to tackle drug abuse.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

  Heroin user

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