More than 300,000 Canadians contract an acute stomach bug every year from the municipally-supplied water that comes out of their taps, some likely ending up in the hospital or even dying, a new government study suggests.
The research also concludes millions of people are still getting their drinking water from substandard municipal and private systems — despite repeated safety warnings after the tainted-water disaster in Walkerton, Ont.
The authors at the Public Health Agency of Canada and Health Canada argue the overall figures show the risk of getting sick from drinking water in Canada remains low.
But they suggest that more municipalities look at implementing multiple, fail-safe treatment “barriers,” shown to be the most effective way to keep water safe. The majority of Canadians get their tap water from such sources.
Almost 1.5 million people, however, are still served by municipal systems that have only one form of treatment or none at all, often drawing on surface water prone to contamination, the researchers say.
A water-safety expert whose organization advised the Walkerton judicial inquiry said she was “shocked” by that number.
Such higher-risk systems were banned in Ontario after tap water contaminated with E. coli killed seven people in Walkerton in 2000, said Theresa McClenaghan of the Canadian Environmental Law Association. She thought everyone else had followed suit.
“(Walkerton) was a huge wake-up call, but here we are 15 years later and as the tragedy and the events recede in time, people start to forget the lessons,” McClenaghan said.
“It’s kind of an inexcusable risk to impose on people.”
There are also another 5.5 million Canadians who rely on private wells or smaller systems, another federal study notes, which leads to about 103,000 gastro illnesses a year.
The research is part of an effort to trace the source of an estimated 20.5 million acute gastrointestinal illnesses that occur every year in Canada, stomach upsets triggered by viruses and bacteria from Norwalk to salmonella.
A previous study attributes four million of these cases to food-borne pathogens, with the rest stemming from causes like person-to-person contact, touching animals and swimming in tainted water.
The gastrointestinal bugs can have minor effects, such as a day or two of diarrhea, vomiting or nausea, but sometimes lead to far more serious cases, notes Katarina Pintar, lead author and the agency’s manager of food-safety policy.
“We consider this to be a burden on the Canadian population,” she said.
A study by Pintar and colleagues published this year suggested the four million food-caused cases result in 11,000 hospitalizations and 238 deaths.
The researchers estimated there are about a tenth as many water-borne illness cases but have yet to come up with an estimate of hospitalizations and deaths specifically for them.
The problem, regardless, is that few of the acute cases are reported to authorities; the figures are all estimates.
In one of the new studies, the government team categorized municipal water systems serving 1,000 people or more according to the level of treatment, then used the results of earlier research on water-caused disease to extrapolate the total number of cases.
They came up with 334,000 illnesses from those larger systems. Using a similar method, they estimated 103,000 cases from smaller systems and private wells.
The methodology was sound, but the data used to reach the estimates are thin, making the results less than definitive, said Ron Hofmann, a civil engineering professor at the University of Toronto who advises water-system operators on safety.
Still, the estimates indicate that drinking water in Canada is very reliable, he said.
“They’ve shown, I believe … that personal hygiene and food are much more important than drinking water for these illnesses,” he said. “Overall, compared to other countries in the world, we have things really good in Canada.”
That’s true for most Canadians whose municipal water systems have multiple forms of treatment, coupling methods like chlorine disinfection, filters, and ultraviolet light, said McClenaghan. New laws mandated that approach in Ontario after Walkerton.
But the story is different for those relying on systems without such protections, she said.
As for people who depend on private wells, they should have their water tested at least twice a year, and use some form of treatment, said McClenaghan. But a 2011 survey found just 27 per cent of people on private supplies tested their water at all.