The Walkerton tragedy of 2000, in which seven people died and thousands fell ill in Ontario because of E. coli infection, shattered the town's confidence in the public drinking-water supply. The crisis also got people across the country questioning the safety of what comes out of their kitchen and bathroom taps. And although the likelihood of such a deadly bacterial mix happening again in Canada is low, drinking water can contain microbes that lead to other, far less devastating illnesses. But little scientific attention and research have been directed to these kinds of nonfatal outbreaks, so there's a lack of understanding of their occurrence and impact. A group of B.C. scientists is out to change that, though, being the first in the nation to study gastrointestinal diseases caused by contaminated water and how they can be prevented.

Giardia lamblia and Cryptosporidium parvum are two microscopic protozoan parasites that ultimately arise from human or animal fecal sources and that can be found in tap water. The first causes giardiasis, better known as beaver fever, which is characterized by diarrhea, abdominal cramps, weight loss, malaise, vomiting, chills, headache, and fever. According to Health Canada, the symptoms usually show up six to 16 days after initial contact and persist for as long as a month. The latter single-celled organism leads to cryptosporidiosis, which has similar symptoms that surface within two to 25 days after infection and usually last one or two weeks, although they can stay for as long as a month.

Judy Isaac-Renton, the director of laboratory services at the British Columbia Centre for Disease Control, explains that there's no statistical data on the prevalence of these illnesses and whether they're linked to environmental factors affecting water supply, like weather conditions, sewage-disposal methods, and agricultural land use. People feeling sick might not go to their doctors, and if they do, they might be told they're suffering from the flu. However, gastrointestinal illnesses could account for as many as one half of all infectious-disease cases in Canada.

Although B.C. has a "very good" safety system in place and recently introduced its Drinking Water Protection Act, Isaac-Renton said that one of the problems in preventing illness is that existing tests are neither reliable nor swift. By the time water is checked for contamination and a boil-water advisory has been issued, that supply has already reached the public.

"We want to test water closer to the source so that we can send an alert before it's too late," said Isaac-Renton, who's heading the new three-year study exploring water quality and waterborne disease. "If there is a potential problem--a weather event or a fecal contamination--we need a faster way of giving people the heads-up. We want quick and early alerts."

Isaac-Renton, who also chairs the water-food-safety subcommittee of the Canadian Public Health Laboratory Network, describes the multidisciplinary study team as a "source-to-tap consortium". It includes members of the BCCDC, Health Canada, Environment Canada, UBC, University of Alberta, and University of Calgary, among others, whose goal is to improve public-health surveillance of drinking water. Funded by the Canadian Institutes of Health Research, the study is based out of the Township of Langley and the Greater Vancouver Regional District.

Giardia and Cryptosporidium in healthy people usually clear up on their own, without treatment, within a month. According to Health Canada, antiparasitic drugs can help those with giardiasis who have compromised immune systems and in whom the illness could develop into a persistent state, while there are no medications to fight cryptosporidiosis. Both parasites can cause more severe symptoms or even death in immunocompromised people, such as transplant patients or those with AIDS or cancer.

Health Canada's Web site ( www.hc-sc.gc.ca/ ) states that, when used as disinfectant, chlorine can reduce the risk of waterborne organisms like Giardia but it isn't effective against Cryptosporidium . People who want to be extra cautious can boil their water for one minute to kill such microorganisms. Bottled water isn't considered a safe alternative to tap water because it's not monitored for either parasite.

The City of Vancouver's engineeringservices department described the overall quality of drinking water in 2003 as "good". "At no time did the percentage of positive coliform samples exceed the 10% maximum stipulated [by] the BC Safe Drinking Water Regulation," the City's Web site says ( www.city.vancouver .bc.ca/ ). "In 2003, the microbiology and the chemistry quality of Vancouver Water conformed to all standards set by both the GCDWQ [Health Canada's Guidelines for Canadian Drinking Water Quality] and the British Columbia Drinking Water Protection Act except for one occurrence with a positive coliform sample." (Coliform bacteria are usually found in the gastrointestinal tract of humans and other vertebrates and are normally harmless; if present in water, they're tested for a subgroup called fecal coliform bacteria, which can indicate contamination by Escherichia coli [E. coli] or related harmful bacilli or viruses. The aforementioned positive sample was not a fecal coliform.)

Vancouver's water comes from mountain rivers, creeks, and streams and is collected by the Seymour, Capilano, and Coquitlam watersheds. Chlorine is used to control bacteria regrowth in the city's water mains. The city also monitors levels of disinfection byproducts: trihalomethanes and haloacetic acids, the first of which is a suspected carcinogen.

Water filters can improve the taste, smell, and appearance of drinking water. According to the Canada Mortgage and Housing Corporation, filters can remove substances like chlorine, mercury, or lead but do not disinfect water or remove microorganisms.

The CMHC ( www.cmhc.ca/ ) stresses that if not used according to the manufacturer's instructions, filters can actually promote bacterial growth. It's essential to replace the filter as often as recommended and in some cases to flush the filter daily with cold, treated drinking water to prevent the buildup of bacterial residue on the filter itself. "Studies have shown that levels of bacteria present in water that has passed through an improperly maintained home filtration device may be up to 2,000 times higher than levels in unfiltered water," the CMHC Web site states.

Filters aren't regulated in Canada. Though we in B.C. aren't likely to experience our own version of Walkerton, maybe boiling our water isn't such a bad idea.