EPA targets nitrogen dioxide emissions near freeways

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The rest of the country may be catching up to California when it comes to limiting emissions of the air toxin nitrogen dioxide.

The EPA last Friday proposed to strengthen the limits on nitrogen dioxide (NO2), an air toxin that the agency says can lead to respiratory illnesses. Nitrogen dioxide is found in emissions from traffic and industrial facilities such as power plants. Even short-term exposure can increase the risk of respiratory effects, particularly among children, the elderly, and people with asthma, according to the EPA.

California already limits NO2 emissions to 30 parts per billion on average annually, while the federal limit would stay at 53 ppb per year under the new regulations.

However, California’s hourly average limit for NO2 emissions is 180 parts per billion, while the EPA has proposed hourly limits of 80-100 parts per billion, and is taking comments on hourly limits as low as 65 ppb and as high as 150 ppb. The EPA is also proposing the use of a different format for calculating hourly averages.

The hourly limits are meant to curb the concentrated short term exposures that communities near highways might experience during peak traffic hours. Concentrations of NO2 are 30%-100% higher near major roads, according to Cathy Milbourn, a spokeswoman for EPA.

The federal proposal would also require states to implement monitoring devices for NO2 emissions particularly targeted at measuring emissions around major roads in areas with large urban populations -- a key issue for Los Angeles, where dense housing and schools are crowded close to freeways.

“We’re updating these standards to build on the latest scientific data and meet changing health protection needs,” said EPA Administrator Lisa P. Jackson. “In addition to limiting annual average concentrations, we’re preventing high NO2 levels for shorter periods of time and adding stronger monitoring in areas near roadways, where the highest levels of NO2 are often found. This will fill gaps in the current standard and provide important additional protections where they are needed most.”

California health advocates greeted the proposal with mixed sentiments. ‘We are pleased with the EPA proposing for the first time a one hour NO2 standard, but we do think it needs to be strengthened to protect kids with respiratory illnesses like asthma,’ said Bonnie Holmes-Gen, senior policy director at the American Lung Assn. of California. Holmes-Gen suggested that the EPA should follow California’s example by limiting the yearly average for NO2 emissions to 30 parts per billion.

The proposal marks the first time in over 35 years that the EPA has strengthened the NO2 limits.

The proposed limits were released just days after a study found a connection between traffic-related nitrogen oxide pollution and the major birth complication preeclampsia.

A public hearing is slated for Los Angeles in August. The public has 60 days to comment on the proposal.

-- Amy Littlefield

Photo: Traffic on major roadways like the 110 Freeway in Los Angeles is a major contributor to NO2 pollution. Credit: Brian VanderBrug/Los Angeles Times