The researchers found that the largest Italian river carried about 4 kilograms of cocaine a day.
Sports teams and workers routinely undergo screening designed to detect illegal drugs. However, Italian researchers have done a drug test on an entire region -- and found that consumption seems to be considerably higher than people admit in drug-use surveys.
This was not the average urine test in a cup, however. They drug-tested a river.
Ettore Zuccato and colleagues at the Negri Institute for Pharmacological Research in Milan measured levels of a cocaine residue called benzoylecgonine (BE) in the Po River and in the sewage water of several medium-sized Italian cities in the region.
The residue is a byproduct of cocaine being metabolized in the human body and cannot be produced from any other source, so it is considered a good environmental marker of drug use.
The results, reported online in the journal Environmental Health, were at least three times higher than official estimates of cocaine use in the Po Valley.
The researchers found that the Po, the largest Italian river, with some 5 million people living around it, steadily carried the equivalent of about 4 kilograms of cocaine a day.
This suggests an average daily use of 27 doses of 100 milligrams of cocaine for every 1,000 people ages 15 to 34 -- the main consumers of cocaine. Readings from the municipal sewer systems yielded similar numbers.
In the Po Valley, that translates into at least 40,000 doses of cocaine being used every day. Yet official national estimates of cocaine use indicate that 15,000 young adults living in the Po Valley admit to taking the drug at least once a month.