A paper published last night in the Journal of Transportation Research Part D: Transport and the Environment identifies how many people are impacted by highway pollution in the United States. The paper finds that 19.3 percent of the U.S. population lives within 500 meters of a high volume road.

The findings are important for public health because regulators have been slow to remedy the ample scientific evidence demonstrating high levels of air pollutants near major roadways.

The research is all the more important in a place like California where the study found that 40 percent of the state’s population lives near high volume roads—the biggest percentage of any state. Yet, air regulators in California have been slow to take initial steps to place air monitors near heavily trafficked roadways.

I’m pleased EPA regulations on nitrogen dioxide air monitors are kicking in by the end of the year, but we still await monitoring of other harmful pollutants by our regulators. I agree with the conclusion of a recent L.A. Times editorial that authorities can no longer ignore the situation.

As the paper points out, the lack of monitors near major roadways is potentially hiding violations of clean air standards—otherwise known as National Ambient Air Quality Standard or NAAQS. Once identified, a region must reduce emissions and “perform more detailed air quality analysis when developing transportation plans.” Thus, until we get these monitors in place to understand the extent of the pollution problem near highways, our regulators are allowing region’s to mask their duties to bring clean air to highway adjacent residents.

Cleaning up this air near highways will not be easy, but will get more difficult the longer we wait with our head in the sand.

The study also has large implications for environmental justice because it found that low-income residents and minority communities are overrepresented in the population near these roadways. The study also found that greater traffic density is associated with increased race and income disparities.

Last night at dinner with some Earthjustice supporters, I tried to explain why our regulators are slow to take action on this health threat. I did not have a good answer, and I doubt the regulators do either. We need swift action to remedy highway pollution, and there is no better place to start than in California.