Background: Analysis of student consumption of illicit drugs (ID) by school population surveys (SPS) provides information useful for prevention, but the results may be influenced by subjective factors. We explored wastewater (WW) analysis to improve the information.

Methods: We used WW analysis to measure ID consumption in eight secondary schools in Italy in 2010-13 (students aged 15-19). Samples were collected from the sewage pipes of the schools during lessons for one week each year. Samples were analysed by mass spectrometry to measure ID and consumption by students was compared to that of the general population.

Results: We found THCCOOH (human metabolite of THC) concentrations in 2010 indicating significant consumption of cannabis in all the schools and benzoylecgonine (human metabolite of cocaine) suggesting a limited consumption of cocaine in all but one school. Morphine was only found in traces, and amphetamine, methamphetamine, ecstasy, ketamine and mephedrone were not detectable. Repeated analysis showed cannabis stable until 2012 with increases in 2013, low cocaine and morphine levels, and none of the other ID.

Discussion: WW analysis suggested that students used amounts of cannabis comparable to the general population, with low, sporadic use of cocaine and opioids, but excluded the use of significant amounts of amphetamine, methamphetamine, ecstasy, ketamine and mephedrone. WW analysis was useful to confirm SPS figures and provides complementary findings for effective prevention strategies. This is the first time WW analysis has been used to investigate consumption of a large number of ID and new psychoactive substances (NPS) in schools.