Canadians warned to stop use of malathion products older than a year

Health Canada has issued a warning to Canadians to stop using pesticides containing malathion when products are more than a year old.

An advisory was issued Wednesday stating chemical changes in the products – even when stored correctly – could pose a health risk for people.

Malathion is a registered insecticide in Canada. It’s mainly used to control insects in agriculture and can also be used in and around the home.

Health Canada said the chemical is effective in killing mosquitoes and other pests without posing unacceptable risks to human health or the environment when used according to label directions.

Over time, however, a toxic chemical called isomalathion can naturally form in the products. This occurs more frequently when stored at elevated temperatures.

Health Canada said it’s possible levels of isomalathion could become a concern, even when proper storage guidelines are met.  

The advisory noted there are ways to test for higher levels of the toxin, but it’s not really feasible for individual Canadians.

People are told to make sure they store any products containing malathion in a cool – around 20-23 C – dry, well-ventilated place away from seed, fertilizer or other pesticides and for no longer than one year.

Health Canada said people should contact their provincial regulatory agency or local municipality for information on how to dispose of household hazardous waste properly in their area.

Exceptions for commercial users

The advisory noted Health Canada does not have an issue with the use of malathion product older than one year when all of the following are met:

• An accredited laboratory test results showing the malathion remains within accepted standards (for example, it meets the World Health Organization specifications)
• The test results are maintained for compliance verification purposes
• The product continues to be used in accordance with the other label directions (including storage conditions)

People are asked to report any adverse events to the manufacturer, who is required by law to report to Health Canada.

Incidents can also be reported directly to Health Canada by completing an incident report form.

The agency is working with manufacturers to modify the labels of products containing malathion to include date information, and the requirement for laboratory testing beyond this date to ensure the product is within acceptable specifications.