Criteria air contaminants (CAC), or criteria pollutants, are a set of air pollutants that cause smog, acid rain, and other health hazards. CACs are typically emitted from many sources in industry, mining, transportation, electricity generation and agriculture. In most cases they are the products of the combustion of fossil fuels or industrial processes.
The history of each criteria air pollutant is listed below:
| Pollutant | Action | Date Added |
|---|---|---|
| Ozone | Ozone included as an "oxidant" standard | 1971 |
| Ozone | Further analysis made revisions to standards necessary | 1979 and 1997 |
| Particulate Matter | listed in Criteria document issued by the EPA | 1996 |
| Particulate Matter | Second External Review Draft of the Air Quality Criteria for PM | 2001 |
| Particulate Matter | Third External Review Draft | 2002 |
| Particulate Matter | Fourth and Final External Review | 1996 |
| Lead | listed as a criteria air pollutant that required NAAQS regulation | mid-1970s |
| Lead | the EPA published a document which detailed the Air Quality Criteria for lead | 1977 |
| Lead | Addendum to the document published | 1986 |
| Carbon Monoxide | The EPA set the first NAAQS for carbon monoxide | 1971 |
| Sulfur Oxides | EPA first set primary and secondary standards | 1971 |
| Nitrogen Oxides | The EPA first set primary and secondary standards for the oxides of nitrogen | 1971 |
Read more about Criteria Air Contaminants: Background, Sections 108 and 109 of The U.S. Clean Air Act, Six Criteria Air Pollutants, EPA Endangerment Findings/ Mass V. EPA, Petition To Add Seven Criteria Air Pollutants
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