Environment Canada researchers have found a dozen different types of toxic drugs and even caffeine in water samples taken from the St. Lawrence River

The study raises many questions about the long-term effects of pharmacological pollution in the country's waterways. "At this point we have detected toxic substances but we don't know what the real toxic effects are," Andre Lajeunesse, one of several researchers involved in the study, said Tuesday. Although the study dealt specifically with the St. Lawrence, drug pollution in waterways is widespread, said Francois Gagne, who authored along with two other researchers the study published earlier this year in the journal Ecotoxicology and Environmental Safety.

"When you're near a city, you're going to see it," Gagne said.

Mercury, PCB and metal contamination has decreased, she said.

"We know that the St. Lawrence is doing much better than it has been for the past 30 years," Saulnier said.

Improved technology means researchers can now distinguish between the different types of pollution in the river.

Twenty years ago studies revealed alarming levels of PCBs in water, she said, and in ensuing years much has been done.

A decade ago scientists worried about pesticide pollution and today, she said, controls have been put in place and pesticide levels have dropped.