Supervisor Chuck Harris can tell if the county is designated as a code red day when he goes out for one of his occasional jogging trips.
"It feels harder to breathe, and it feels like you're not quite getting as much [air] as you are on other days," said Harris (D-Broad Run).
Supervisor James Burton (I-Mercer) notices when fine-particulate matter, which he says looks like black dirt, appears on cars and decks in the mornings, while Supervisor Mark Herring (D-Leesburg) looks out on the horizon to measure air quality.
"It seems like the air quality is so poor, you can see how bad it is, especially during the summer. You just can't see very far," Herring said.
Herring, Harris and Burton are concerned about Loudoun's air quality, which is affected by pollution produced within the county but also by pollution coming from nearby counties and states.
"Air doesn't know political boundaries," Herring said. "It migrates across the state. It requires our federal legislatures to act."
The Environmental Protection Agency extended the 1999 deadline to 2005 for the Washington metropolitan region to meet public health standards for ground level ozone, a key ingredient of urban smog. The health standards for six pollutants are part of a 1990 amendment to the Clean Air Act, which carries federal sanctions if the standards are not met, including loss of federal highway funds and an increase to emission offsets for certain businesses locating to the area.
The pollutants include lead, particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide and ground level ozone.
THE METROPOLITAN Washington region, which is allowed 161.8 tons of nitrogen oxide emissions per day, is classified as a non-attainment area for ground level ozone. The classification increased to severe non-attainment in July, when the Sierra Club environmentalist group won a suit against the deadline extension.
The non-attainment classification, in part, results from the amount of nitrogen oxides that are transported into the region from several out-of-state power plants. Several of the plants release four to 10 times the amount of nitrogen oxides as modern plants, since they were grandfathered under existing legislation.
Nitrogen oxides are a precursor of ground level ozone, since it has to combine with sunlight to create the ozone.
"None of our pollution sources emit ozone," said Craig Lowrance, air monitoring specialist for the Virginia Department of Environmental Quality (DEQ). "It takes high heat and sunlight. That's why the summer is the peak season for ozone. A hot sunny day will have a higher ozone concentration than the exact same situation with cloud cover."
High concentrations of ground level ozone can cause shortness of breath, coughing, headaches, nausea and eye and throat irritation, according to the DEQ.
"We have to breathe the air and the pollutants these plants put into the air," Harris said.
THE CLOSEST POWER plant to Loudoun is the Dickerson Power Plant in Montgomery County, Md., which is one to two miles from Leesburg across the Potomac River.
The Harvard School of Public Health recently studied five power plants in the Washington metropolitan region, including the Dickerson plant. The study found that more than 250 area deaths, 40 in Northern Virginia, and thousands of respiratory illnesses are linked to particulate matter released from the plants and that the percentage of deaths could be reduced by 75 percent if the plants implemented current pollution control equipment.
"Ashburn is downwind from Dickerson plant," Burton said. "When the wind is northwest, whatever comes out of the smokestack ends up in the Leesburg and Ashburn area."
Burton sees the Dickerson plant as a concern, but no more so than the coal-fired plants in the southwestern part of the state and older plants outside the state. Plants in West Virginia, Kentucky, Ohio and the Ohio Valley transport nitrogen oxides into the county's air. Most of the plants burn coals as a fuel source and are grandfathered from meeting current emission standards.
"Because of that, 23 states have to reduce nitrous oxide by 85 percent," Burton said. "They are all a problem. Taken together they are a serious problem."
THE DEQ MEASURES ozone in the Washington metropolitan region by monitoring six pollutants in various sites, including Ashburn. The ozone monitor, which is in a gray shed near Broad Run High School, recorded 16 ozone violations between June 10 and Aug. 10 for 12 code red days and four code purple days. Code red means the air quality is unhealthy for sensitive groups and for people with asthma. Code purple points to unhealthy air quality.
The number of violations in the county increased from last year when the ozone monitor recorded nine 8-hour exceedences. The monitor measures both 1-hour and 8-hour exceedences. The 8-hour measure is for a longer period of time for a lower concentration of nitrogen oxides, but is harder to meet, Lowrance said.
"Clean air and clean water are important things to have a healthy life, and we should do what we can to protect it," Herring said.