WASHINGTON – Ozone pollution in the Baltimore-Washington area is slowly improving, but it remains the biggest and most enduring air pollution problem in the region, said a state environmental official and a scientist who has studied the problem for years.
The Baltimore metropolitan region has been in a “non-attainment” status — meaning it fails to meet federal clean air standards — for ozone since the 1970s.
“It is the major atmospheric pollution issue,” said Russ Dickerson, a professor of meteorology at the University of Maryland, College Park. Dickerson’s air chemistry group has studied regional air quality issues extensively.
“Last year, Anne Arundel County was third worst in America for ozone pollution,” Dickerson said. “Houston was first, Los Angeles was second, and Anne Arundel County was third.”
While ozone may be the area’s best-known air pollutant, it is not something that comes directly out of a smokestack or a tailpipe. Rather, ozone is actually the product of two other pollutants — nitrogen oxides and volatile organic compounds — that react in hot sunlight.
Because ozone is a product of these two “precursor” pollutants, environmental officials are able to measure their emissions rather than directly measuring ozone emissions, even though ozone is classified as a criteria pollutant under the Clean Air Act.
Angelo Bianca, the deputy director of the Maryland Department of the Environment’s Air and Radiation Management Administration, said ozone pollution is the only remaining major air pollution problem facing the state.
“Long term, the state has made good progress,” Bianca said. “Our only remaining problem, if you look at it from a federal standard . . . is ground- level ozone.”
Bianca pointed out that a significant amount of both ozone precursor pollutants come from “non-stationary” or mobile sources, such as cars, trucks, boats, trains and as an assortment of lawn care equipment like mowers, leaf blowers and weed whackers.
He pointed to a 1990 study that showed mobile sources — chiefly cars and trucks — accounted for fully 46 percent of observed nitrogen oxides pollution in Maryland, while stationary point sources accounted for another 43 percent of the total.
Even more dramatically, he said the same report found that mobile sources accounted for 52 percent of volatile organic compound pollution while stationary point sources accounted for just 8 percent of the total. The remaining 40 percent came from stationary area sources, including paints, inks, cosmetics and solvents.
Solving the ozone problem requires dealing with mobile-source issues.
“You have to account for the fact that in your planning to reduce ozone precursor emissions. . .that people are continuing to travel more, which means more gasoline usage and to deal with that, there are a number of things that have been done and will be done,” Bianca said.
He added that progress is being made, based on the number of ozone air- quality violation days experienced by the region during the summer months. He said that is borne out by a plot of ozone violation days vs. 90 degree days.
“As you plot that curve over time, the trend is downward,” Bianca said, so that unlike in the past, “it is not necessarily a given that every time you have a high-temperature day, you have an ozone-violation day.”
Dickerson agreed that the situation is “very slowly” getting better.
“The observations and statistics support his (Bianca’s) assertion” that the ozone situation is improving, Dickerson said.
But he noted that even last year when regional air quality was very good, there were still ozone pollution violation days in the Baltimore-Washington area.
“Last year was an unusually clean year. . .nevertheless, we still violated the ambient air quality standard four or five times,” Dickerson said.
The current federal standard is 125 parts of ozone per billion parts of air. That standard corresponds to the familiar air quality index of 100. Any air quality index reading at or above 100 corresponds to a “code red” or unhealthy air quality, according to the Maryland Department of the Environment’s “Ozone Information Center” web page.