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The first Canadian National Ambient Air Quality Objectives were developed in the mid-1970s. These objectives were set for various air pollutants.The NAAQO had three levels indicating severity (maximum desirable, acceptable and tolerable levels) and also evaluated effect levels (maximum desirable, acceptable and tolerable levels).
The violations occurred between 2007–2008 and the state of Hawaii suggested these should be exempt from regulatory actions due to an 'exceptional event' (volcanic activity). Since 1980 the national concentration of SO 2 in the ambient air has decreased by 83%. [16] Annual average concentrations hover between 1–6 ppb.
Ambient air quality criteria, or standards, are concentrations of pollutants in the air, and typically refer to outdoor air.The criteria are specified for a variety of reasons including for the protection of human health, buildings, crops, vegetation, ecosystems, as well as for planning and other purposes.
The National Ambient Air Quality Standards (NAAQS) govern how much ground-level ozone (O 3), carbon monoxide (CO), particulate matter (PM 10, PM 2.5), lead (Pb), sulfur dioxide (SO 2), and nitrogen dioxide (NO 2) are allowed in the outdoor air. [6] The NAAQS set the acceptable levels of certain air pollutants in the ambient air in the United ...
1970 – Clean Air Act (Extension). Major rewrite of CAA, setting National Ambient Air Quality Standards (NAAQS), New Source Performance Standards (NSPS) Hazardous Air Pollutant standards, and auto emissions tailpipe standards. 1970 – Williams-Steiger Occupational Safety and Health Act (created OSHA and NIOSH)
The standards for determining whether an area is in "attainment" (compliance) or "non-attainment" (non-compliance) for six major pollutants are the National Ambient Air Quality Standards (NAAQS). These are required by law to be reviewed every five years, as new scientific information becomes available on the health and property impacts of ...
The Clean Air Act (USA) (1990) requires the EPA to review its National Ambient Air Quality Standards every five years to reflect evolving health effects information. The Air Quality Index is adjusted periodically to reflect these changes.
In order to meet these needs, the individual pollutant concentrations are compared to Alberta's Ambient Air Quality Objectives (AAQOs). The national AQHI is used most of the time; however, if hourly air pollutant concentrations are higher than Alberta's AAQOs, the AQHI value is replaced (overridden) with the appropriate "High" or "Very High ...