While cocaine and cannabis remain the most popular illicit drugs, new synthetic substances are being detected at a rate of about one a week — a fast-rising trend, according to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA).
A total of 49 new synthetic drugs were detected by law enforces in 2011, and more than another 50 so far this year.
For the period 2005-2011, the total had been 164.
"More than ever before, young people are exposed to a plethora of powders and pills," the agency said in a statement.
"Data from emergency rooms, toxicology reports and drug treatment centres indicate that the associated risks are not always well known by the users."
The new psychoactive substances are sold on the illegal drug market but also sometimes on the Internet as so-called "legal highs".
But the report warned they often contained "obscure" chemicals or mixtures of chemicals, and said they had caused several acute medical emergencies and deaths.
"The number of products containing multiple psychoactive substances appears to be rising, and some test purchase samples have been found to include both controlled and non-controlled substances," the report said.
"Consumers of these products are likely to be both unaware of what they are consuming and ignorant of the health and legal implications."
The agency also reported a decline in overall cocaine and heroin use, but noted a worrying rise in HIV infection among heroin-injectors in Greece and Romania.
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