Even light doses of glyphosate can cause disease in organs later on, says a biologist opposed to spraying the herbicide to kill weeds and young hardwoods in New Brunswick and elsewhere.

"Glyphosate accumulates in all our organs," said Thierry Vrain, a soil biologist and former president of the International Federation of Nematology Societies.

The New Brunswick forest industry uses glyphosate to kill maple, oak and other hardwood growth, and by NB Power uses it to kill hardwood growth near transmission lines.

The main ingredient in Roundup, glyphosate is also sprayed on farmland around the world, despite a finding by the cancer and water branch of the World Health Organization that it is "probably carcinogenic to humans."

Hangs around in soil

Vrain, who worked for Agriculture Canada for 30 years and has a doctorate in plant pathology, said that the company that invented glyphosate thought it was biodegradable and would last a only few days in the soil before disappearing.

"It's a lot longer than that," said Vrain, who was recently invited to speak in Fredericton to groups opposed to glyphosate spraying.

He said a Swedish study found traces of glyphosate remained in soil two years after it was applied.

Once introduced into the environment, glyphosate is remarkably stable, he said.

Although Vrain believes glyphosate is a risk to human health, he said no research has been done on humans.

Research done on animals, however, shows cause for concern, he said.

In recent years, research on animals, including rats and pigs, has found they become chronically diseased even with small doses of glyphosate, Vrain said.

He said the animals have developed cancer, kidney and liver disease and obesity.

Can only speculate about humans

"All we can do is speculate with all the data that we have on research from animals."

The European Union is deciding whether to ban glyphosate, and this year California moved to add it to its list of potentially cancerous chemicals.

Despite critics' concerns about the safety of glyphosate, its effects on the water supply, forest diversity and the environment, the herbicide is registered in 100 countries.

In New Brunswick, a report by the acting chief medical officer of health found that in 2016, nearly 29,000 hectares of forest were treated with glyphosate.

But Dr. Jennifer Russell also said there was no increased health risk for New Brunswickers.

"We acknowledge that some uncertainty about glyphosate exists, but based on our review, exposures in New Brunswick are similar to or less than elsewhere," she said.