BioEd Online

A study of drug chemicals in sewage water suggests that the level of cocaine use could be many times the figure suggested by questionnaires.

Ettore Zuccato of the Mario Negri Institute for Pharmacological Research in Milan and his colleagues took river and sewage samples from four medium-sized Italian cities. They analysed these samples for cocaine and its main metabolite, called bezoylecgonine, which is found in urine.

They then scaled this up to estimate the total amount of drugs travelling through the water system in a day, using figures of overall water flow.

This approach revealed that the 5 million people living around the Po, Italy's largest river, consume four kilograms of cocaine each day. This translates into at least 40,000 daily doses of this drug, or about 200,000 lines of cocaine, the team reports in Environmental Health¹.

"It's higher than what we were expecting," says Zuccato.

High numbers

In contrast, a 2001 survey by the Italian Welfare Ministry indicated that the roughly 1.5 million young adults living near the river take cocaine at least 15,000 times a month. In the survey, 1.1% of those aged 15-34 admitted to having used cocaine at least once in the preceding month. But researchers did not know any more precise details of their drug use.

Zuccato's sewage survey helps to add to the data. It is the first time that a community's drug abuse has been measured in this way, Zuccato says. Though he adds that the same technique has been used for pharmaceuticals. In 2000, Zuccato's team measured the amounts of medications such as antibiotics in river and sewage waters². "The levels were as expected or lower," Zuccato says.

The researchers now plan to search for other illegal drugs in waste water, although some drugs might be difficult to distinguish from legitimate pain relief medication. "It will be difficult to distinguish between heroine and morphine because there are similar metabolites," Zuccato explains.

Other drugs, such as marijuana, produce too few stable metabolites to be easily detected in sewage and river water.