The City of Ottawa is monitoring how animals and plants in the Ottawa River are affected by chemicals that remain in sewage after it is treated and discharged into the waterway.

Dave McCartney, the manager of wastewater and drainage services for the city, said even though the sewage and landfill runoff discharged into the river is treated to remove most of the harmful bacteria and heavy metals, thousands of chemicals remain.

And while bacteria in the sewage have recently garnered much media attention because of contamination at Ottawa's public beaches, the other chemicals are less frequently discussed.

"I think the public is probably unaware … that many of the chemicals they use around their homes or the pharmaceuticals they take themselves ultimately end up in the natural environment and are very difficult to handle," McCartney said. "We really don't know what the long-term effects of these things are in the environment. Some are persistent and don't break down."

He added that it's impossible to monitor what people put down the drain, but he thinks public education about the proper way to dispose of hazardous waste is having a positive effect.

In the meantime, McCartney said, the city tests the water and sediments of the river regularly for metals and organic chemicals and monitors the health of the organisms in the sediments at the bottom of the river, where many chemicals tend to accumulate if they are not water-soluble.

Chemical testing not mandatory

That is not required by the Ministry of the Environment, and very few other cities do it, he added.

So far, the results of the testing have been good.

"We're finding very very little going on — having very little impact," McCartney said.

Jules Blais, an environmental toxicologist at the University of Ottawa, said in other rivers, scientists have noticed changes in fish hormone levels that have been blamed on chemicals in sewage runoff and can affect the ability of the fish to reproduce.

That should worry humans, too, he said.

"Many of these substances that we release into the environment come back to us because we are all downstream from someone else's drain," he said. "What goes around comes around."