University professor Peter Limb said his wife became unwell when a “glyphosate truck” sprayed a nearby street on a windy day.
“The spray wafted to us, even though we were in the church garden,” he said.
The herbicide is widely used by councils despite the World Health Organisation warning almost a year ago that the chemical “probably” causes cancer.
Mr Limb reported the incident to Planning Minister John Day in December and again on February 12 when he saw another “glyphosate truck in action”.
He wrote to the Shire of Kalamunda and asked why the council continued to put residents’ health at risk.
“Who is responsible for this action and why are staff (or contractors) advised not to do this in windy weather?” he said.
“We believe such a carcinogenic material should not be used at all; this is dangerous practice.”
Several European countries recently banned the use of glyphosate, a chemical commonly found in weed killers sold to the public.
A Shire of Kalamunda spokeswoman said the council was monitoring developments nationally and internationally.
“The pesticide glyphosate – the active ingredient in Roundup – is used to control weeds throughout the Shire including verges, reserves, traffic islands and fire breaks,” she said.
“In order to manage the use of glyphosate, a range of controls are in place including restrictions to when glyphosate can be used – not near pedestrians or in windy weather.”
She said other restrictions related to applying the lowest concentration required and wearing protective equipment.
Glyphosate is used throughout the Shire of Mundaring “wherever total broad weed control is required and in strict accordance with usage instructions”.
Shire chief executive Jonathan Throssell said measures such as high-pressure steam were not as effective as traditional measures in controlling weeds.
“Weed control is very important to ensure grasses for parks and ovals can thrive and allow active and recreational play,” he said.
“Weed control is also critically important for the natural environment to ensure native flora can thrive, as weeds can overtake natural bushland.
Mr Throssell said glyphosate was a common domestic weed killer found in many residential sheds and garages.
“We are committed to ensuring the health and safety of our community, employees and contractors,” he said.
“Should the advice regarding use of glyphosate or other chemicals change from their current approved status by the Department of Health, the Shire will undertake appropriate changes,” he said.
A Worksafe spokeswoman advised workers to take the required safety precautions when using chemicals.
“There is no proof glyphosate is carcinogenic and we have not received any reports of workers becoming ill using Roundup,” she said.The Australian Pesticide and Veterinary Medicine Authority (APVMA) – the peak body for pesticide control – and the Federal Department of Health are re-assessing the risk of glyphosate to humans and their investigation is due for completion in a few months.