For the first time in two years, air quality reached such an unhealthful level over the weekend in parts of San Diego County that it prompted a Stage One smog alert, officials said Monday.
During a Stage One alert, people with respiratory problems should restrict their activities and everyone should avoid strenuous exercise, said Lynn Eldred, spokeswoman for the San Diego County Air Pollution Control District.
The unhealthy pollution levels on Saturday were the result of a "unique and unusual" weather pattern, combined with unhealthy air from Los Angeles and several large brush fires in San Diego, Eldred said.
A Stage One smog alert is issued when ozone levels exceed 200 on the federal government's pollution standard index for at least one hour, according to Eldred. A Stage Two alert is issued when the ozone level exceeds 275 on the pollution standard index.
Air quality from Del Mar to Point Loma, from the coast to about two miles inland, reached 240 on the pollution standard index from 4 to 8 p.m. on Saturday, she said. The last Stage One smog alert in San Diego was on Oct. 5, 1985.
Average Much Lower
On an average day, San Diego's air falls within 75 to 150 on the pollution standard index, according to Eldred.
A rare easterly wind pattern on Saturday had been expected to be strong enough to keep the unhealthy air flowing down from Los Angeles away from the coastal areas, but the offshore flow proved to be stronger than first thought, Eldred said.
"We had offshore smog come in from the Los Angeles area," she said. "We hadn't expected this; it was not in the forecast. We thought the winds would be strong enough to haul it (the smog) all the way offshore, but because of a unique and unusual pattern this did not turn out to be the case."
"The fires added a lot of particulates to the air, adding to what people's lungs already had to cope with," Eldred said. "There was also the heat factor, which made the air seem heavier."
Of the warning against physical activity, Eldred said, "Basically, don't give your lungs anything more to cope with than what they already have to survive. If it had happened during the week, we would have contacted the schools in the affected area to warn them to restrict the children's physical activities."
Air quality is expected to improve steadily over the next few days, Eldred said.