Chemical wood preservatives are commonly used to enhance wood durability, and if effectively applied, they can increase the life expectancy of wood by a factor of five to ten times. Classified as pesticides, chemical preservatives achieve decay control as a direct result of their significant toxicity. Although the potency of these products varies according to the type of preservative, all are poisonous to some degree, and if misused can be potentially hazardous to humans and other forms of life. In either case, proper selection, use and disposal of chemical preservatives and treated wood are essential to reduce risk to human health and the environment. Most chemicals registered by Agriculture Canada for use as wood preservatives are classed as very toxic and potentially hazardous pesticides.
Misused preservatives can adversely affect a broad range of organisms.
Also, wood preservatives may contain chemicals and impurities which can cause long-term adverse biological effects. Although the most likely sources of environmental pollution by wood preservatives are industrial wood treatment and storage facilities, the misuse of even small volumes of preservatives by the homeowner can result in harm to humans and other organisms, as well as significant environmental contamination. Creosote is a complex mixture of toxic chemicals, which can have both immediate and chronic effects on exposed organisms. The polyaromatic hydrocarbon components of creosote accumulate in exposed aquatic organisms or can persist in sediments for long periods of time. Bottom-feeding fish exposed to creosote contaminated sediments can contain high concentrations of polyaromatic hydrocarbons, some of which can be carcinogenic.