In the context of air standards, the term "standard" refers to a regulatory limit placed on the presence of a contaminant in the ambient (outside) environment. Ontario's air standards are based on the best scientific information available and are set at levels that safeguard human health and the natural environment.
Setting air standards is a multi-step process that considers a full range of scientific issues and perspectives.
Most of the standards developed under O. Reg. 419/05 are based on the ministry's Ambient Air Quality Criteria (AAQCs). AAQCs are effect-based concentration levels with variable averaging times (e.g., 24 hours, 1 hour, 10 minutes). The effects considered include health, odour, vegetation, soiling, visibility and corrosion.
