History of California's Ambient Air Quality Standards

This page reviewed November 24, 2009.

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 Air Resources Board (ARB). 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 ARB.
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	ARB-funded study finds that exposure to air pollution retards children's lung function growth rate.
	ARB 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)

For a general history of California's Air Quality, please click here.

For more info on Ambient Air Quality Standards please contact Dr. Linda Smith
at (916) 327-8225.