EPA Regulates Short-Term Exposure to Air Pollutant Nitrogen Dioxide

The new one-hour standard is intended to protect Americans from peak short-term exposures to nitrogen dioxide, NO2, which is formed from vehicle, power plant and other industrial emissions, and contributes to the formation of fine particle pollution and smog.

The new one-hour standard supplements the existing annual average standard of 53 ppb.

This is the first revision to the national air quality standard for nitrogen dioxide since the current standard was adopted in 1971 and it includes the first network of roadside monitors for any motor vehicle pollutant.

"For the first time ever, we are working to prevent short-term exposures in high risk NO2 zones like urban communities and areas near roadways," said EPA Administrator Lisa Jackson.

"This new one-hour standard is designed to protect the air we breathe and reduce health threats for millions of Americans," Jackson said.

EPA is establishing requirements for an NO2 monitoring network that will include monitors at locations where maximum NO2 concentrations are expected to occur, including within 50 meters of major roadways, as well as monitors sited to measure the area-wide NO2 concentrations that occur more broadly across communities.

Residential apartment buildings line the Cross Bronx Expressway, New York City (Photo by Joshua Siebert)

Under the new monitoring requirements to measure NO2 levels, monitors must be located near roads in cities with at least 500,000 residents.

Existing community-wide monitoring will continue in cities with at least one million residents.

Working with the states, Jackson says the EPA will site at least 40 monitors in locations where communities are vulnerable to elevated levels of NO2. Larger cities and areas with major roadways will have additional monitors.

Based on the existing monitoring network, the EPA expects to identify or designate areas not meeting the new standard by January 2012.

New monitors must begin operating no later than January 1, 2013. When three years of air quality data are available from the new monitoring network, EPA intends to redesignate areas as appropriate.

Charles Connor, president and CEO of the American Lung Association, welcomed the new standard, calling it a good first step. but said the EPA's original proposal last summer was more protective.

"After waiting 38 years, we had frankly hoped for a stronger, more protective standard. Their decision allows areas to have nitrogen dioxide concentrations that remain hazardous to the millions of people who will have to breathe them," Connor said. "Their final decision, unlike their proposal of last summer, allows twice as many days when nitrogen dioxide will spike to dangerous levels."

"Unfortunately," he said, "that burden is likely to fall hardest on those who can least bear it - children, older adults, people with lung disease, as well as people with low incomes, and communities of color."

Connor pointed to a review of the evidence of the threats to health from living near a highway issued January 13 by the Health Effects Institute, a research center funded by the motor vehicle industry and EPA.

The HEI quoted the conclusions of an expert panel that breathing the nitrogen dioxide and other pollutants from highway traffic increased the risk that a child's asthma would get worse. Strong evidence warned that pollution from traffic may even increase the risk that children could develop asthma, or worsen their lungs' ability to function.

A residential area next to the highway serving the SeaTac airport near Seattle and Tacoma, Washington (Photo by Derrick Coetzee)

For older adults and people with cardiovascular disease, living near a highway may increase the risk of early death, the review showed.

"Neighborhoods near major highways are often home to people with lower incomes, as well as communities of color," Connor said. "Many busy highways pass through dense urban neighborhoods or near schools. Those communities often have higher prevalence of lung disease, putting them at even greater risk from breathing traffic exhaust."

The Institute's report states, "Based on a synthesis of the best available evidence, the Panel identified an exposure zone within 300 to 500 meters from a highway or major road as the area most highly affected by traffic emissions and estimated that 30% to 45% of people living in large North American cities live within such zones."

Jackson said the new standard is intended to protect the health of these very populations - people with asthma, children and the elderly living near major roads and highways.

The EPA points to current scientific evidence linking short-term NO2 exposures, ranging from 30 minutes to 24 hours, with adverse respiratory effects including increased asthma symptoms, more difficulty controlling asthma, and an increase in respiratory illnesses and symptoms.

Studies also show a connection between short-term exposure and increased visits to emergency departments and hospital admissions for respiratory illnesses.

"Improving air quality is a top priority for this EPA," said Jackson. "We're moving into the clean, sustainable economy of the 21st century, defined by expanded innovation, stronger pollution standards and healthier communities."

The Clean Air Act requires EPA to set national ambient air quality standards for "criteria pollutants." Currently, nitrogen oxides and five other major pollutants are listed as criteria pollutants. The others are ozone, lead, carbon monoxide, sulfur oxides, and particulate matter.

All areas presently meet the current (1971) NO2 national ambient air quality standards, with annual NO2 concentrations measured at area-wide monitors well below the level of the standard of 53 parts per billion.

Annual average ambient NO2 concentrations, as measured at area-wide monitors, have decreased by more than 40 percent since 1980, the EPA states in connection with this rule. Currently, the annual average NO2 concentrations range from approximately 10-20 ppb.

EPA expects NO2 concentrations will continue to decrease in the future as a result of a number of mobile source regulations that are taking effect. Tier 2 standards for light-duty vehicles began phasing in during 2004, and new NOx standards for heavy-duty engines are phasing in between 2007 and 2010 model years. Current air quality monitoring data reflects only a few years of vehicles entering the fleet that meet these strict NOx standards.

Click here to read the new final rule regulating nitrogen dioxide.

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