Pesticide spray drift occurs when a pesticide (for example, herbicide, insecticide, fungicide) stays suspended in air long enough to drift off the area being sprayed. Spray drift occurs downwind of the application site and, generally, the amount of drift decreases rapidly as distance from the area being sprayed increases. In residential areas, spray drift could result from applications to lawns, gardens and parks or from applications on nearby agricultural areas.
The potential for drift depends on many factors, including weather conditions and the type of spray equipment being used. That's why Health Canada's Pest Management Regulatory Agency ensures that pesticide labels have directions for use that include advice on how to minimize spray drift.
Under normal use conditions specified on the label, pesticide residues from spray drift are not a concern for users or bystanders. However, an excessive amount of spray drift into non-target areas has the potential to affect human health or the environment. For this reason, the impact of pesticide spray drift on people and the environment, which includes non-target plants and wildlife, is taken into account as part of the pesticide risk assessment process when a pesticide is considered for registration or is being re-evaluated.
Human health risk assessments of pesticides examine direct exposure to users (both professional applicators and residential users) and bystanders who may be nearby during application. The potential for exposure to pesticide residues deposited on the ground or foliage after application is also considered. Health Canada must ensure that these anticipated exposures would not pose a health concern. Additional precautions are usually included in the label directions to further reduce potential human exposure to spray drift, such as directions to avoid spraying when bystanders are present.
Environmental risk assessments examine how a product travels through air, soil and groundwater and how long it stays in those areas. The potential for a product to adversely affect non-target plants and wildlife, both on the ground and in the water, is also considered. When necessary, Health Canada requires specific directions on the product label to minimize any potential effects to non-target plants and wildlife.
Other examples of label directions that Health Canada may require to further minimize the potential for both human and environmental impacts from spray drift include:
If you wish to apply pesticides to your lawn or garden, it is important to be aware of jurisdictional (provincial, municipal, local) regulations concerning the use of pesticides. You can minimize pesticide use as well as the potential for exposure by:
To further reduce the potential for spray drift:
It is good practice to notify neighbours of your intent to spray pesticides. They may choose to take additional precautions such as closing windows, removing and/or covering outdoor toys and eating areas, or by simply avoiding being in proximity to the area to be sprayed.
You may also choose to hire a professional pesticide applicator who is licensed/certified by your provincial regulator. Professional applicators are trained and certified to properly and safely use pesticides, including how to use appropriate application methods and choose equipment that minimizes spray drift. Professional applicators must follow provincial requirements for buffer zones and maximum allowable wind speeds for pesticide application.
Each pesticide has its own specific vapour component, which accounts for the odour detected near application sites. Although some pesticides can have strong odour that may be disagreeable, the odour itself is not harmful and tends to dissipate quickly. Fertilizers may also be a source of strong odour.
Health Canada restricts how pesticides are to be used. Best management practices are encouraged and promoted through applicator training initiatives and label statements. Health Canada and provincial authorities have developed national standards for pesticide education, training and certification in Canada, which include factors affecting drift and methods to reduce potential for drift to non-target areas during application. There are also compliance and enforcement programs in place that monitor the use of pesticides.
Please visit Health Canada's Web site for further information on the topics discussed in this document.