10 August 2005: Recreational drugs down the drain

The discovery of cocaine by-products in an Italian river challenges official figures on national cocaine consumption and has prompted similar analysis of other drugs.

The consumption of illicit drugs is rife but there are no direct methods to determine the extent of the problem. Estimates rely on social, medical and legal statistics but researchers at the Mario Negri Institute for Pharmacological Research in Milan have adopted a novel approach. Targeting one specific drug, they measured the amounts of cocaine and its principal human metabolite, benzoylecgonine, in the River Po in northern Italy.

They reasoned that the majority of the drug excreted from users would eventually be conveyed to surface waters, which act as a local depository. The researchers used liquid chromatography/mass spectrometry, and monitored selected ions that were unique to each compound and found benzoylecgonine and cocaine at 25ng/L and 1.2ng/L, respectively.

While these figures may not seem particularly notable, they translate into a cargo of 4kg of cocaine per day. Data from wastewater treatment plants from four cities dispersed across Italy are consistent with these figures.

There is no other way than through human consumption that either compound could enter the river. The ratio of benzoylecgonine to cocaine was in the expected range, based on known amounts in human urine, and the concentrations were similar over several days, ruling out dumping in the river.

The daily total in the river was extrapolated to 40,000 doses per day for people living in the river’s basin, or 27 doses for every 1000 young adults, compared with official estimates of a mere 15,000 doses per month.

’The next stage is to address new drugs such as cannabis and ecstasy,’ team spokesman Ettor Zuccato told Chemistry World. ’The idea in general is to focus on the main urinary metabolites as a starting point.’ The researchers plan to use the same analytical technique for these studies, saying that it requires minimum extraction clean up but offers very high sensitivity and specificity.

Heroin, however, would be more problematical since one of its metabolites is morphine. ’There is a legal hospital use of morphine and before starting we would like to have an estimate of its environmental burden,’ said Zuccato. Steve Down