The waterways of several Canadian cities saw substantial increases in toxic ammonia levels last year, and the prime culprit in at least two cases, according to municipal officials, is household urine.

Figures released this month by Environment Canada show major hikes in ammonia levels in the waterways around Montreal, Vancouver, Ottawa, Quebec City and St. John's.

The Newfoundland capital, where sewage is discharged untreated into the ocean, saw a 62-per-cent increase in ammonia levels in its harbour.

"There's no real discharge limit," city engineer Lynn Ann Stapleton said. "This is the way it's been for 500 years, right, since [explorer John] Cabot came over."

In Victoria, the only other major Canadian city that emits untreated effluent, ammonia levels rocketed up in 2006 but stayed constant last year.

Municipal officials in both coastal cities say one of the main causes is the tonnes of urine that gets flushed down toilets, but they also say better measurements are responsible for a large part of the statistical upswing.

Environment Canada considers ammonia to be toxic, but Canadian cities are not currently obligated to remove it from the sewage they release.

"We basically rank on the scale of a lot of Third World countries that are still under development," John Werring of the David Suzuki Foundation said.

St. John's and Victoria are both building sewage processing facilities, and long-awaited federal rules will require most municipalities to have at least secondary wastewater treatment by 2010.

However, while secondary treatment removes almost all coliform bacteria, it leaves much of the ammonia.

"As the levels increase, we'll be seeing more and more blooms of harmful algae and seaweed that are choking up sewage treatment plant pipes and harbours and bays," Werring said.

Cities such as Calgary and Edmonton that employ tertiary treatment on their sewage have dramatically curtailed aquatic ammonia levels.

Werring added that even with the new rules, which provincial environment ministers are expected to formally accept this fall, Canada's waterways won't get much cleaner right away, since some communities will be allowed up to 30 years to improve their sewage treatment.