Canadians use hundreds and thousands of kilograms of pesticides -weed killers and insecticides- on their lawns.

Other users -parks, golf courses, sod farms- also use huge quantities of the stuff.

• More: Pesticides by the numbers

The trouble is it doesn't all stay on the grass. It's getting into our water, our rivers, even into the rain.

In the summer of 1998 in Lethbridge Alberta, the rain was laced with the common weed killer 2,4-D. It drenched both city and farms.

The City of Toronto tests the Humber River for lawn pesticides

In Southern Ontario, similar chemicals have turned up in waterways, possibly the Humber River in Toronto where the city is testing for lawn pesticides.

"They're herbicides and insecticides, so if they were able to get into the streams at very high concentrations they could kill fish or affect plants themselves," says John Struger, a scientist with the Canadian Centre for Inland Waters.

He has analyzed urban streams and detected nine kinds of lawn pesticides in them. In one instance, a bug killer exceeded by 140 times the provincial guideline set to protect water.

John Struger is a scientist with the Canadian Centre for Inland Waters

Dr. Kelly Martin is an emergency room doctor at the Royal Victoria Hospital in Montreal. "Children are … at increased risk from pesticides," she says.

Martin is also an epidemiologist and a member of Health Canada's Pest Management Review Agency. She's about to tell a parliamentary committee of a number of studies linking pesticides and cancer.

The studies Dr. Martin has reviewed deal with children exposed to lawn pesticides:

"We have five or six good studies that show that if you use lawn pesticides on your lawn or garden one to four times a year your child has a five to six times increase of developing leukemia."

"Children are … at increased risk from pesticides," says Dr. Kelly Martin

But Wendy Rose, with the Urban Pest Management Council, cites a different study -by Health Canada- which found no elevated risk of cancer to agricultural workers using pesticides.

"We are the first people to want to make sure that those products are okay for use on the market," she says.

"Our industry is the most regulated in Canada," Rose adds. "Every product, before it goes on the market, is approved by the Pest Management Regulatory Agency. And if at any time the PMRA feels there are potential adverse effects for a product they remove it."

"Our industry is the most regulated in Canada," says Wendy Rose

The Turfgrass Institute at the University of Guelph is recognized around the world for its research on pesticides and grass. Gerry Stephenson is a professor of biology there.

"Pesticides are toxic chemicals," he says. "They are particularly toxic to weeds and insects we want to control."

Stephenson has tested people for chemicals after they have shuffled through turf that's been sprayed with pesticide:

"You can get detectable residues that have penetrated the skin, and fortunately, with 2,4-D, 99 per cent of what gets through the skin is excreted within 48 hours."

"Pesticides are toxic chemicals," says Gerry Stephenson

Dr. Martin notes: "These are adults. These aren't children who are playing around for an hour on the grass."

She says that 20 per cent of the people who arrive in a hospital emergency room with toxic pesticide exposure are children who've crawled on a lawn after it's been sprayed "safely."

The industry is confident that registered pesticides have an adequate margin of safety. Dr. Stephenson agrees, but he says pesticides should be used more discriminately.

Dr. Stephenson says pesticides should be used more discriminately

"We have to educate the lawn care companies," he says. "They don't believe that, a lot of them, that if they're not applying the pesticide they think maybe their customer would think they're not doing anything."

Toronto's Parks and Recreation department manages one of the largest inventories of urban parks in Canada - 31 square miles, from ravines and golf courses to sports fields and play areas.

Traditionally, parks departments have been among the largest users of pesticides. Seeking a balance between good-looking green spaces and healthy living led Toronto to adopt a Pesticide Reduction Program this summer.

'Aquacide,' is a truck-mounted device that is a new take on an old technology

It employed some unconventional pest-control measures like Aquacide, a truck-mounted device that is a new take on an old technology. It uses steam to kill weeds. No warning signs, no toxic chemicals, no chemical residues.

Another approach is to leave the ground cover in some park areas uncut. Weeds become wildflowers creating an urban pocket of natural habitat where birds and small animals have returned.

But Wendy Rose is not impressed.

"I've seen some communities, as an environmental initiative, reduce their use of pesticides. Then two, three or eight years later have to go and use more product," she says.

"Citizens are complaining about municipal weeds blowing onto their property," says Wendy Rose

"Citizens are complaining about municipal weeds blowing onto their property."

But many complaints have been about pesticides and there have been concerns expressed about chemicals and the long-term potential effects of these chemicals.

Toronto is not the first city to reduce the use of pesticides in its parks.

Calgary and Vancouver have done it too. Waterloo, Ont. has virtually eliminated pesticides in its public places. Nine municipalities in Quebec have passed by-laws restricting use of pesticides by institutions and homeowners as well.

So what's a person with a lawn to do? Some lawn care companies are sensitive to the excessive use of pesticides.

"Pesticides are not the foundation of our program, fertility is," says Ken Pavely with Nutri-lawn.

"Pesticides are not the foundation of our program, fertility is," says Ken Pavely

"We use all kinds of different fertilizers to achieve a good thick healthy lawn," Pavely continues. "That's the best defence against weed encroachment, and insect and disease infestation."

Rather then blanketing your lawn with a combination of fertilizer and weed control, the pesticide is sprayed directly on the weeds as needed using a special trigger.

"A lot of people are under the misconception that when we spray a lawn we're going to prevent weeds from coming up with a weed control. That's not the case," Gravely says. "So the best defense against a weed infestation in a lawn is a thick thick turf."

Cheryl Shour goes even further. Her company offers customers chemical-free lawn care.

"I was shocked by what was used and there was no alternative to using chemicals," she says.

Cheryl Shour's company offers customers chemical-free lawn care

So Shour offers an organic lawn care program with four visits for $200. But she admits that using no chemicals means there's no quick fix.

"This time of year, which is perfect for seeding, we also put down an organic fertilizer. Once is all you really need in the fall," says Shour. "We also educate the homeowner on healthy maintenance practices which includes cutting nice and long to encourage healthy root growth."

So if you're interested in reducing pesticide use on your lawn, check out our tips.