Northwest Clean Air Agency

NWCAA: Serving Island, Skagit and Whatcom Counties

The Clean Air Act, last amended in 1990, requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards:

Primary standards set limits to protect public health, including the health of “sensitive" populations such as asthmatics, children, and the elderly.
Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.

NATIONAL AND STATE AMBIENT AIR QUALITY STANDARDS

The EPA has set National Ambient Air Quality Standards for six principal pollutants, which are called "criteria" pollutants and are listed below. Units of measure for the standards are parts per million (ppm) by volume and micrograms per cubic meter of air (µg/m3).

POLLUTANT	NATIONAL PRIMARY STANDARDS	NATIONAL SECONDARY STANDARDS	WASHINGTON STATE STANDARDS
Carbon Monoxide (CO) 8-hour 1-hour	9 ppm 35 ppm	9 ppm 35 ppm	9 ppm
Lead Quarterly Average	1.5 µg/m3	1.5 µg/m3	1.5 µg/m3
Nitrogen Dioxide (NO₂) Annual Mean	0.053 ppm	0.053 ppm	0.05 ppm
Particulate Matter (PM₁₀) Annual Average 24-hour	50 µg/m3 150 ug/m3	50 µg/m3 150 ug/m3	50 µg/m3 150 ug/m3
Particulate Matter (PM_2.5) Annual Average 24-hour	15.0 µg/m3 65 ug/m3	15.0 µg/m3 65 ug/m3	15.0 µg/m3 65 ug/m3
Ozone 8-hours 1-hour	0.075 ppm 0.12 ppm	0.075 ppm 0.12 ppm	0.08 ppm 0.12 ppm
Sulfur Oxides Annual Average 24-hour 1 3-hourr 1 1-hour 5-minute	0.03 ppm 0.14 ppm None None None	None None 0.50 ppm None None	0.02 ppm b 0.1 ppm 0.4 ppm 0.80 ppm c
a Eight hour ozone standard went into effect on September 16, 1997, but implementation is limited. b 0.25 not to be exceeded more than two times in any 7 consecutive days. c NWCAA standard