California Air Resources Board

SACRAMENTO – Today the California Air Resources Board (ARB) approved new, stricter standards for nitrogen dioxide (NO2), a pollutant associated with increased asthma and cardiovascular disease. NO2 is a pungent gas that, when combined with fine airborne particulate matter, contributes to the reddish-brown haze characteristic of smoggy air in California.

"Today's action continues California's leadership on air quality programs and health protection," said ARB Chairman Dr. Robert F. Sawyer. "The standards are set with a margin of safety to protect the youngest Californians and other vulnerable populations."

The Children's Environmental Health Protection Act (Senate Bill 25, Escutia), passed by the state legislature in 1999, requires the ARB, in consultation with the Office of Environmental Health Hazard Assessment (OEHHA), to "review all existing health-based ambient air quality standards to determine whether, based on public health, scientific literature and exposure pattern data, these standards adequately protect the health of the public, including infants and children, with an adequate margin of safety." As a result of the review requirement, the ARB today adopted the new NO2 standards:

• The 1-hour-average state standard for NO2 is lowered from 0.25 parts per million (ppm) to 0.18 ppm, not to be exceeded.
• A new annual-average state standard is established for NO2 at 0.030 ppm, not to be exceeded.

NO2 is a concern particularly for asthmatics and for infants and children. Higher concentrations of NO2 occur near roadways compared to ambient background levels, and raise health concerns. Finally, NO2 besides being a common outdoor air pollutant, is becoming an increasing health concern in indoor environments, where the average person spends most of their time.

Sources of NO2 include high temperature combustion processes such as motor vehicle engines and power plants. It can also be the product of atmospheric processes where nitrogen oxides react with ozone to create NO2. Indoor concentrations are caused by sources such as gas appliances, and un-vented heating systems.

Today's changes to the state NO2 standards are not expected to alter the attainment status for most areas of California. All are in compliance for the state 1-hour standard. The South Coast Air Quality Management District has occasionally exceeded the new annual standard, but current control efforts should produce future compliance.