Cocaine residue in Italian water reveals more users than official estimates


The levels of cocaine residue in flowing water in Italy suggest that many more people take the drug than official national estimates previously suggested. A study published today in the open access journal Environmental Health reports on a new tool used to measure the levels of a cocaine by-product excreted in urine, and present in rivers and in flowing sewage water. This new method provides evidence that about 40,000 doses of cocaine are consumed every day in the Po valley - according to official estimates for this area, only 15,000 users admit to taking the drug at least once a month.

Current official estimates for illegal drug use, including cocaine, are based on population surveys, medical records and crime statistics. These methods are known to be unreliable and to under-estimate the extent of illegal drug use, mainly because they rely on users self-reporting drug use, a socially censured behaviour, which users tend to be elusive about.

Ettore Zuccato, from the Mario Negri Institute for Pharmacological Research in Milan, Italy, and colleagues tested a new tool to measure a cocaine residue called benzoylecgonine (BE), present in flowing river and sewage waters because it is excreted in the urine of cocaine users. The residue is a by-product of metabolism in the human body, and cannot be produced by other means. The researchers measured the levels of BE in the river Po and in the sewage water of medium-sized Italian cities. Their results show that the Po, the largest Italian river, with five million people living in its vicinity, steadily carried the equivalent of about 4 kg of cocaine per day. This would imply an average daily use of at least 27 doses of 100 mg of cocaine for every 1,000 young adults of 15 to 34 years of age the main consumers of cocaine. In the Po valley, this would translate into a least 40,000 doses being used every day by young people. This number greatly exceeds official national estimates, according to which 15,000 young adults living in the Po valley admit to taking the drug at least once a month. The researchers' data from medium-sized Italian cities is consistent with the figures found in the Po valley.

"Our main goal was initially to verify how our consumption estimates compared with official figures. We expected our field data on cocaine consumption to give estimates within the range of the official estimates, or perhaps lower, but certainly not higher", write Zuccato et al.

Their results demonstrate that new methods are needed to assess the number of illegal drug users. These figures are necessary to follow changes in drug use trends and help tackle drug abuse. Although the new method implemented by Zuccato et al. looks like a promising candidate, the authors warn "clearly, the method implemented here needs to be refined and validated, and adapted for other drugs of abuse before it can become a general tool for monitoring drug abuse."

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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