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revised April 15, 2009

How Pesticides Affect the Environment

What happens to pesticides in the environment?

Pesticides have to be released into the environment to kill an intended, targeted pest.

Once applied to a lawn or garden, some of the pesticide may travel into the air, soil, groundwater, and surface waters and be carried away from the lawn or garden. Just how fast a pesticide moves off-site from where it’s applied depends on its chemical and physical characteristics. Also, pesticides in the environment can change or degrade due to reactions caused by light, chemical reactions, or biological reactions.

Risk to non-target species

Pesticides can kill beneficial soil bacteria, earthworms, snails, frogs, birds, fish, honeybees, and other valuable species. Sometimes instructions on the product label include information about risks to these ‘non-target species.’

Pesticides in water samples

In 1999, researchers from Environment Canada found a number of lawn care pesticides (including mecoprop, 2,4-D and diazinon) in water samples from both the Humber and Don Rivers in Toronto.

Lawn care pesticides have also been detected in surface waters in Hamilton, Guelph, and other urban areas. The waters of urban rivers, creeks and ponds do contain lawn care pesticides, and the concentrations are higher after rainfall.

In some cases, the highest levels of pesticides (diazinon and 2,4-D) measured in urban ponds and streams have, at times, exceeded the levels set by governments to protect aquatic life. However, there isn’t enough data to tell us how pesticide use affects plants and animals and the overall health of our ecosystems.

For more information: Guelph Turfgrass Institute


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Revised: April 15, 2009

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