RESEARCHERS sifting through raw sewage in 19 European cities have found the highest cocaine use in Antwerp, while the Nordics prefer methamphetamines and Amsterdam unsurprisingly leads in cannabis use.

From the biggest-ever drug analysis of samples taken from Europe's sewers, the research team deduced that the continent uses about 350kg of cocaine every day while marijuana remains the most popular illicit drug.

"Through research into the sewer, we can determine how big the drug market in a city is," co-ordinator Kevin Thomas of the Norwegian Institute for Water Research said of the study covering cities in 11 European countries.

The team took samples from the inlets of 21 sewage treatment plants servicing a combined population of some 15 million people on seven consecutive days from 9 March, 2011 and analysed them in the lab.

The results, published on Thursday in the journal Science of the Total Environment, revealed the highest average cocaine use in the Belgian port city of Antwerp followed by Amsterdam (Netherlands), Valencia (Spain), Eindhoven (Netherlands), Barcelona (Spain), London (UK), Castellón (Spain) and Utrecht (Netherlands).

The Dutch cities of Amsterdam, Utrecht and Eindhoven showed the highest sewage loads of ecstasy, though the authors said Utrecht's figures were probably spiked by drug dumping in a police raid on an ecstasy factory two days prior to the study.

Antwerp and London also had high levels of ecstasy use, but none was detected in Castellón, Umeå (Sweden) or Stockholm (Sweden).

The study said the highest levels of methamphetamine use were measured in Helsinki and Turku in Finland, Oslo (Norway) and Budweis in the Czech Republic.

Amphetamine use was highest in Eindhoven and Antwerp.

in the Dutch capital, which is a popular soft-drug tourist destination.