Pesticides are designed to kill or control harmful or unwanted living organisms. They can take the form of chemical substances, biological control organisms, or other forms. Pesticides serve important functions, including: improving quality and yield in agricultural production; preventing and controlling insect infestations; controlling the spread of harmful diseases and toxins; controlling noxious plants; and protecting pets from fleas and ticks. There are risks, too. Even when applied properly, pesticides and their breakdown products can contaminate soil, water and air, harming non-targeted fora and fauna. Some pesticides can persist in the environment long after being applied, and can accumulate in the body tissues of wildlife, becoming more concentrated up the food chain.
Among other matters, the Pesticides Act regulates what pesticides can be sold or used in Ontario, and requires licences in order to sell, apply or operate a business that employs people who apply pesticides commercially. In addition, permits are required to use certain higher-risk pesticides. In 2008, the Act was amended to ban the use of cosmetic pesticides. You can read the full legislation here. The Act is administered by the Ministry of the Environment and Climate Change.