Outdoor, or ambient, air quality standards define the maximum average amount of specific pollutants that can be present over a period of time.
The Clean Air Act Amendments of 1970 instruct the U.S. Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six air pollutants — particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide and lead. Primary standards must protect public health, including at-risk groups, with an “adequate margin of safety.” Secondary NAAQS are designed to safeguard plants, crops, animals and buildings.
In 1959, California enacted legislation requiring the state to establish air quality standards and necessary controls for motor vehicle emissions, but attaining NAAQS takes precedence.
The state and federal limits on the level of specific air pollutants are detailed in the Table of Ambient Air Quality Standards on the California Air Resources Board (CARB) website.
Quick Links
For more information on the attainment status of California air districts, visit CARB’s Ambient Air Quality Standards Designation Tool webpage.
For details on federal standards, see the EPA’s NAAQS Table.
For additional information on state standards, visit CARB’s California Ambient Air Quality Standards page.
NAAQS Review Process
The EPA is required to review and, if necessary, revise each of the NAAQS at five-year intervals to make sure they are based on the most recent scientific findings. The process takes about five years and includes a review of scientific literature and an assessment of evidence, risk and policy implications. The Clean Air Scientific Advisory Committee reviews the information and makes recommendations to the EPA administrator, who issues proposed standards. Public comments are collected throughout the process. The EPA makes the final determination.
Attainment
The EPA designates areas as meeting (attainment) or not meeting (nonattainment) each of the NAAQS. Federal law requires that all states attain federal standards. States must develop general plans to attain and maintain them. State and local air quality management agencies prepare specific plans for attaining the standards in nonattainment areas. States submit the plans, called State Implementation Plans or SIPs, to the EPA. Failure of a state to reach attainment by the target date can trigger penalties, necessitate additional air pollution control measures and require the EPA to prepare a federal implementation plan if the state does not submit an acceptable SIP.
Ventura County is in attainment for all standards except the following:
Ventura County Nonattainment Pollutants
| Ozone | 1-hour | State |
| 8-hour | State and Federal | |
| Particulate Matter/PM 10 | 24-hour | State |
| Annual Arithmetic Mean | State |