A picturesque part of the Rideau Canal running through downtown Ottawa is now on a list of contaminated federal sites, Parks Canada announced Thursday.

That dubious designation is the result of tests done on sediment from the canal bed between the Ottawa Locks and Bronson Avenue. The tests were conducted after the discovery of heavy metals such as lead and cadmium, as well as polycyclic aromatic hydrocarbons, which have been linked to various cancers.

The latest round of tests was conducted to identify the extent of the contamination, and to be able to put in place measures to protect the environment, Parks Canada said.

'Not unexpected'

Parks Canada calls the discovery of contaminated sediment "not unexpected" given the long history of industrial use and the urban location of that part of the canal. Over the last century the downtown stretch of the canal was home to a paint factory and has seen both trains running along its edge and steam-powered boats hauling industrial goods.

Parks Canada, the federal department in charge of the canal, said it would work with the City of Ottawa and the National Capital Commission to find ways to deal with the affected section of the UNESCO World Heritage Site.

The risk to human health is low, according to the department, as long as people don't have direct contact with the sediment at the bottom of the canal. Boating, paddling, skating and recreational use of the canal pathways will continue to be encouraged, Parks Canada said.

Parks Canada temporarily halted repairs along a section of the canal after workers turned up canal-bed toxins while laying bricks last November.

Repairs resumed in the winter but were restricted so as not to disturb the sediment.

Parks Canada said future construction work would proceed with mitigation measures in place to protect the environment and public safety.

Thursday's statement didn't mention the canal's marine life, which includes carp, muskies and other species popular with urban fishers.

Earlier this year, Parks Canada acknowledged that fish can ingest sediments, even though fishing is monitored by the Ontario government. The province told CBC News last spring it was assessing the situation.