History of California's Ambient Air Quality Standards

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The following chronology shows when California State agencies took major actions on ambient air quality standards. Starting in 1969, actions listed were taken by the California Air Resources Board (CARB).

Note: After each pollutant, the allowable level and duration are shown in parentheses.
Abbreviations are as follows:
  • AQS = Air Quality Standard
  • CO = Carbon Monoxide
  • PM = Particulate Matter
  • NO2=Nitrogen Dioxide
  • SO2 = Sulfur Dioxide
  • H2S = Hydrogen Sulfide
  • µg/m3 = Micrograms Per Cubic Meter

1955

Los Angeles County Air Pollution Control District establishes an air pollution alert system to prevent disaster.
 
  • First Alert Levels
    • Ozone (0.5 ppm)
    • NOx (3 ppm)
    • SOx (3 ppm)
    • CO (100 ppm)

1959

The first statewide air quality standards were set by the Department of Public Health for total suspended particulates, photochemical oxidants, sulfur dioxide, nitrogen dioxide, and carbon monoxide.
 
  • 'Adverse' Level: "Oxidant Index" (0.15 ppm, 1 hr)
  • Particulates (Visibility < 3 Miles), SO2 (0.3 ppm, 8 hr and 1 ppm, 1 hr)
  • 'Serious' Level: CO (30 ppm, 8 hr and 120 ppm, 1 hr)
 The table of standards includes notes regarding health and welfare effects from exposure to ozone, NO2, hydrocarbons, lead, photochemical aerosols, sulfuric acid, and ethylene. The table also states that carcinogens (e.g., polycyclic aromatic hydrocarbons, arsenic, chromium) should be "as low as possible."

1962

  • Ethylene (0.1 ppm, 8 hr and 0.5 ppm, 1 hr)
  • H2S (0.1 ppm, 1 hr)
  • NO2 (0.25 ppm, 1 hr - Adverse Level)
 The table of standards is revised to include a note regarding health and welfare effects from exposure to hydrogen fluoride.

1967

California Air Resources Board created. Subsequent AQS are set by CARB.

1969

Air quality standards are set by the ARB for total suspended particulates, photochemical oxidants, sulfur dioxide, nitrogen dioxide, and carbon monoxide.
 
  • Oxidant (0.1 ppm, 1 hr), H2S (0.03 ppm, 1 hr), NO2 (0.25 ppm, 1 hr)
  • Suspended PM (60 µg/m3, Annual and 100 µg/m3, 24 hr)
  • CO (20 ppm, 8 hr), Particulates (Visibility < 10 Miles), SO2
    (0.04 ppm, 24 hr and 0.5 ppm, 1 hr)

1970

  • CO (10 ppm, 12 hr and 40 ppm, 1 hr)
  • Lead (1.5 µg/m3, 30-Day Average)

1974

SO2 (0.1 ppm, 24 hr); "Photochemical Oxidant" changes to "Oxidant as Ozone."

1975

SO2 (0.04 ppm, 24 hr)

1976

  • Lead (1.5 µg/m3, 30-Day Average) - Retained from 1970 Action
  • Sulfates (25 µg/m3, 24 hr)
  • For Lake Tahoe Air Basin Only: CO (6 ppm, 8 hr) and Visibility Reducing Particles
    (Not Less Than 30 Miles)

1977

SO2 (0.05 ppm, 24 hr)

1978

Vinyl Chloride (0.01 ppm, 24 hr) - Due to the carcinogenicity of vinyl chloride, this level is not a threshold but is the minimum detectable (in 1978).

1982

CO (9 ppm, 8 hr and 20 ppm, 1 hr)

1983

PM10 or Respirable PM (50 µg/m3, 24 hr and 30 µg/m3, Annual Geometric Mean) - These standards replace the suspended PM standards.

1984

SO2 (0.25 ppm, 1 hr)

1988

Ozone (0.09 ppm, 1 hr)
 California Clean Air Act Goes into Effect

1989

CO (9 ppm, 8 hr and 20 ppm, 1 hr) - Retained from 1982 Action

1991

SO2 (0.04 ppm, 24 hr)

1992

NO2 (0.25 ppm, 1 hr) - Retained from 1969 Action

1995

SO2 (0.25 ppm, 1 hr) - Retained from 1984 Action

2000

CARB-funded study finds that exposure to air pollution retards children's lung function growth rate.
 CARB reviews all AQS based on Childrens Environmental Health Protection Act.

2002

  • PM2.5 or Fine PM (12 µg/m3, Annual Arithmetic Mean)
  • PM10 (20 µg/m3, Annual Arithmetic Mean
  • Sulfates (25 µg/m3, 24 hr) - Retained from 1976 Action, Monitoring Method Revised          
2005
  • Ozone (0.070 ppm, 8 hr)
  • Ozone (0.09 ppm, 1 hr) – Retained from 1988 Action
2007
  • NO2 (0.18 ppm, 1 hr and 0.030 ppm, annual)

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