University of Maryland scientists say they have found a bright side to the great blackout of August 2003 that darkened the homes and workplaces of 50 million people in parts of the Midwest, Northeast and Canada.
The idling of electric power plants across the affected region resulted in drastically healthier air and bluer skies downwind, including the Baltimore-Washington corridor, the researchers said.
Sampling by aircraft 24 hours after the blackout began found a 90 percent reduction in sulfur dioxide and a 50 percent cut in ozone levels. Visibility increased by more than 25 miles.
The findings could lend new support to efforts by Maryland and other eastern states to force emissions cleanups at upwind power stations.
"This is good stuff," said Kendl P. Philbrick, Maryland's secretary of the environment. "This is what we've been saying all along. It's not a model, not a meteorologist's dream. [The pollution cuts] actually happened."
Philbrick said the Ehrlich administration generally supports the Bush administration's efforts to address air pollution issues, which have included moves to allow utilities to increase capacity without being sued for not making costly emissions improvements.
But the state is trying to convince federal officials that Maryland suffers too much from air pollution blowing in from elsewhere.
"We're saying, 'Hey look, we need help here. You've got to do more ... because we are in a special area. There's no one else in the country like us; no one suffers like we do with regard to this,'" Philbrick said.
A spokesman for the power industry, however, warned that using the College Park study to argue for tougher emissions rules for coal-fired power plants could backfire.
Scott H. Segal, director of the Electric Reliability Coordinating Council, said that stiffening those rules "has a direct implication for the ability to maintain power plants."
It could decrease their reliability and increase the cost of electricity, he said, "and that has a lot more direct health impacts than a temporary decline in emissions."
13 years in the works
The College Park study, to be published in the next issue of Geophysical Research Letters, was led by Lackson Marufu and Russell Dickerson, chairman of the meteorology department.
It grew out of a 13-year-old campaign, funded mainly by the Maryland Department of the Environment, to build a detailed understanding of air pollution patterns in the Baltimore-Washington area.
From May through September, College Park scientists board a specially equipped twin-engine aircraft in the morning and fly upwind of the urban corridor to measure pollution levels in air that is blowing toward the big cities.
In the afternoon, they fly in the downwind side to study the cities' contribution to those pollution levels.
On Aug. 15 last year, after a morning flight over Northern Virginia and Cumberland, the researchers realized that the northeast blackout, which began the prior afternoon, offered a unique opportunity.
"We had ideas of what the power plants were contributing to regional air quality," said Brett F. Taubman, a graduate student in chemistry who was aboard the plane that day. But those ideas came from multiyear measurements and computer modeling.
"This was the first opportunity to directly measure a large scale-back like this. And the results were far greater than we ever imagined," Taubman said.
The scientists flew to Selinsgrove, in central Pennsylvania, which was in the path of air blowing in from the blacked-out region. The differences in pollution levels there were immediately apparent, both on the instrument readouts and in the visibility outside the windows.
Compared with pollution levels measured earlier that day over Virginia and Western Maryland -- both downwind from unaffected power plants -- sulfur dioxide levels near Selinsgrove were 90 percent lower, ozone levels were 50 percent lower and light scattered by airborne particles dropped 70 percent.
Less ozone pollution
Later, as the cleaner air passed over Baltimore, Philadelphia and New York, it produced far less ozone pollution than had been forecast for that day.
"We had forecast 125 parts per billion" in Maryland, Taubman said, "but they only reached 90 parts per billion that day ... and 90 ppb is really quite low considering the surface temperatures and meteorological conditions that day."
Taubman said the most drastic reductions were among pollutants most closely linked to power plants. Levels of soot and carbon monoxide -- more typical of automotive sources -- remained steady.