Traces of cocaine, cannabinoids, nicotine and caffeine have been found in the Roman air, according to a report released recently by the Institute of Atmospheric Pollution at Rome’s national research agency Consiglio Nazionale di Ricerca (CNR).

The institute's findings, published in the scientific journal Environmental Pollution, were part of the Ariadrugs project that measured psychotropic drugs in the air in eight major Italian urban centres: Bologna, Florence, Milan, Naples, Palermo, Rome, Turin and Verona, from May 2010 to May 2011.

Turin's air had the highest concentrations of cocaine, followed by Naples, Rome and Milan. Turin topped the league table in all four categories, with Palermo at the opposite end. After Turin, there were high levels of cannabinoids – such as marijuana and hashish – in Bologna and Florence, something the institute attributes to the large student populations in both cities.

The drug levels, which are too low to have an effect, reveal seasonal trends. Although cocaine and nicotine rates are stable throughout the year, the use of marijuana and caffeine soars over the winter months, which researchers suggest could be related to issues such as seasonal affective disorder.

The results of the year-long report are set to be used to inform public health and legal policy.

In 2007 an air quality study by the same research agency revealed the presence of airborne cocaine in Rome, with the highest levels of the drug detected in the capital's S. Lorenzo district.