Fears that glyphosate, which the New Brunswick forest industry uses to kill maple, oak and other hardwood growth, might be dangerous to water are unwarranted, says a toxicologist from the University of Guelph.

Len Ritter, a professor emeritus of toxicology, said he has worked with herbicides and chemical residue his entire career.

He said government restrictions designed to protect drinking water from glyphosate contamination should be reassuring to the public.

"I think we're all concerned about the quality of water," Ritter said Monday on Information Morning Moncton.

Spraying near reservoir

Ritter was interviewed after Moncton Mayor Dawn Arnold asked the province to stop spraying glyphosate near the Turtle Creek reservoir, which provides drinking water to 100,000 residents.

The spraying for J.D. Irving Ltd. is permitted until Sept. 5.

NB Power also uses the spray to kill plant growth along transmission lines.

​Glyphosate was declared "probably carcinogenic to humans" by the International Agency for Research on Cancer, a branch of the World Health Organization, in 2015.

Used all over

Despite critics' concerns about the safety of the chemical, its effects on the water supply, and the changes it causes to forests, gysophate is registered in 100 countries.

It is widely used in forestry to kill hardwood growth that might interfere with softwood seedlings, and in agriculture to kill weeds.

Ritter said many of the studies on the effects of herbicides are done by industry, then submitted as part of the regulatory process. There is no reason for the public not to trust the studies because of who sponsored them, he said.

"The likelihood that that's going to unduly influence the outcome of the particular study, I don't think is a realistic concern," he said. "I just don't think that's likely to happen."

Under government restrictions, aerial spraying of herbicides cannot occur within 3.2 kilometres of where a municipal water supply is collected.

The water quality is measured before the spraying and after it's over to make sure it has not been contaminated, Ritter said.

But Elizabeth May, federal Green Party leader, said spraying the herbicide in a watershed area is outrageous.

"Glyphosate is not a product without health risks for human beings," she said in an interview with Information Morning Fredericton. "It's a product that should not be used across Canada."

Even the buffer zone around the sources of water supply is no assurance against the herbicide drifting with the wind.

"They should be very cautious about applications of glyphosate," said May, who was in New Brunswick to talk about the environmental issues related to the proposed Energy East pipepline.

"They should be very careful that it is not used in places where people are exposed to the pesticide."

Long-term, low-dose exposure

Most of glyphosate uses are agricultural, said Ritter, who has worked with Health Canada and the World Health Organization in the regulation of toxic chemicals in food.

"So we have maximum residue limits, that is, there are registered permissible levels of glyphosate that might appear as residue in foods."

Ritter said most or the exposure humans would have to the herbicide would be through the food supply.

"Any contribution that would come from water, in the unlikely event that some were to creep into the water, it would still be relatively small compared the amount to which we're exposed to every day as approved food use," he said.

In June, Health Canada said it would be re-evaluating the herbicide, but it's not yet known when the result will be released