Cocaine Rivers Make Headlines

Studies of cocaine levels in European rivers have revealed that levels of drug use in the community may be much higher than estimated by police authorities. In a paper published in the journal BMC Environmental Health in August this year, Italian scientists reported the detection of cocaine in samples from the River Po in northern Italy and several urban wastewater treatment plants around the country.

Four water samples from the River Po were collected on different days, with each sample being a composite of 5 x 500 ml volumes collected 30 minutes apart. Composite samples were also collected from influent wastewater at treatment plants in four medium-sized towns in different areas of Italy (total volume 2 litres, collected every 20 minutes over 24 hours). The samples were analysed for cocaine and its major urinary metabolite benzoyl-ecgonine (BE). All samples were positive for both cocaine and BE. Average levels in river water were 1.2 ng/L for cocaine and 25 ng/L for BE. In wastewater, levels of cocaine ranged from 42 to 120ng/L, and BE from 390 to 750 ng/L. Levels of cocaine use in the community were estimated from the concentration of BE, assuming that a single dose was 100 mg. The results suggested cocaine use at the level of 2 to 7 doses per 1,000 persons/day or 9 to 27 doses per 1,000 persons/day if only young adults were considered (15-34 year age group). These estimates are about 80 times higher than official figures.

The findings prompted international media coverage and led to the commissioning of a similar study in London by a British newspaper. The Italian research team sampled the river at two locations downstream of major sewage treatment plants in London and found levels of BE similar to those in the Italian study. Comparison with official UK figures suggested cocaine use in London was at least 15 times higher than previously estimated. The researchers have suggested that monitoring of drug levels in wastewater may be a more accurate way of estimating trends in use than the current method of anonymous questionnaire surveys.