Criteria Air Contaminants and Related Pollutants

CAC, in particular, refer to a group of pollutants that include:

• Sulphur Oxides (SO_x);
• Nitrogen Oxides (NO_x);
• Particulate Matter (PM);
• Volatile Organic Compounds (VOC);
• Carbon Monoxide (CO); and,
• Ammonia (NH₃)

In addition,

• Ground-level Ozone (O₃) ; and
• Secondary Particulate Matter (PM)

Are often referred to among the CAC because both ground-level ozone and secondary particulate matter are by-products of chemical reactions between the CAC.

CAC are produced from a number of sources, including burning of fossil fuels, and it is because of these shared sources that CAC are grouped together. Information on CAC emissions is collected every year within the National Pollutant Release Inventory (NPRI) starting in 2002. Prior to this, information was collected every five years within a separate inventory process dedicated to just the CAC.