Carcinogenicity Classification of Five Pesticides by the International Agency for Research on Cancer (IARC) March 2015

On March 20, 2015, the World Health Organization's (WHO) International Agency for Research on Cancer (IARC) published a summary of results of their hazard classification of five pesticides. The herbicide glyphosate and the insecticides malathion and diazinon were classified as probably carcinogenic to humans. The insecticides tetrachlorvinphos and parathion were classified as possibly carcinogenic to humans. The full report has not yet been released. Health Canada will review the full report once it is available.

It is important to note that these hazard classifications are not health risk assessments. The levels of human exposure, which determine the actual risk, were not taken into account. Pesticides are registered for use in Canada only if the level of exposure to Canadians does not cause any harmful effects, including cancer.

Before a pesticide is approved for use in Canada, it must undergo a thorough science-based risk assessment and meet strict health and environmental standards, and the product must have value. This includes the examination of both short and long term (lifetime) animal toxicity tests that assess the potential for the active ingredient to cause cancer or genotoxicity, reproductive and developmental toxicity, including effects of pesticide exposure on the developing child, and studies that characterize the unique exposures of children.

A variety of environmental toxicity studies are also examined including toxicity to birds, bees and aquatic organisms.

If the specified use of a product poses risks of concern to human health, future generations or the environment, it is not registered for use in Canada. These same standards apply when a registered product is re-evaluated. Pesticides registered in Canada regularly undergo a 15-year cyclical re-evaluation to ensure that they continue to meet modern standards for human health and environmental protection and provide value.

Glyphosate

Health Canada's Pest Management Regulatory Agency recently published its Proposed Re-evaluation Decision document for pest control products containing glyphosate for public consultation. The document proposes continued registration of products containing glyphosate for sale and use in Canada with implementation of further risk reduction measures. The findings of the re-evaluation, including the required assessment of carcinogenic risk of glyphosate, will provide context regarding the WHO (IARC) hazard classification.  Currently, no pesticide regulatory authority in the world considers glyphosate to be a carcinogenic risk to humans.

Malathion

A review of the mosquito control use of malathion was completed by Health Canada's Pest Management Regulatory Agency under its re-evaluation program in 2003. Based on the health risk assessment, which took into account the potential hazard from animal studies and the likelihood of human exposure, malathion is not considered to pose a cancer risk in humans as a result of its use to control mosquitoes in residential areas, when used according to label directions. This conclusion is not changed by the recent WHO (IARC) hazard classification, as pesticides are registered for use in Canada only if the level of exposure to Canadians does not cause any harmful effects, including cancer.

Parathion

Parathion is not registered for use in Canada.

Diazinon

The re-evaluation decision on diazinon in 2009 required the phase-out of most uses of diazinon due to health and environmental risk concerns, with the exception of soil drench and ear tag applications, which were found to be acceptable for continued registration with additional mitigation measures. This conclusion is not changed by the recent WHO (IARC) hazard classification, as pesticides are registered for use in Canada only if the level of exposure to Canadians does not cause any harmful effects, including cancer.

Tetrachlorvinphos

A review of tetrachlorvinphos was completed by Health Canada's Pest Management Regulatory Agency under its re-evaluation program in 2004.  Health Canada's assessment indicated no human health risks of concerns when the product is used according to label directions. This conclusion is not changed by the recent WHO (IARC) hazard classification, as pesticides are registered for use in Canada only if the level of exposure to Canadians does not cause any harmful effects, including cancer.