Hot, stagnant conditions with a high of 91 are expected to cause unhealthy ground-level ozone levels for the third consecutive day on Wednesday.
The Department of Environmental Protection and the Southwest PA Air Quality Partnership declared an "code orange" Air Quality Action Day on Monday and Tuesday. Ever worsening temperatures are forecasted Wednesday for parts of the Pittsburgh region.
The first code orange of 2015 occurred June 12.
“When we have very high temperatures, sunshine, clear, dry air caused by high pressure; that builds up ground-level ozone,” said John Poister, spokesman for Pennsylvania DEP in Pittsburgh.
The department uses a standardized air quality index, which uses colors to give daily air quality levels. Green signifies good air, yellow suggests moderate pollution and orange, like this week, means there are unhealthy pollution levels for sensitive people. Code red equates unhealthy air for all.
“The problem becomes difficult for young children and the elderly, and those with respiratory problems, such as asthma or emphysema, to be affected by air pollution,” Poister said. “We ask that on a code orange air action day that those people try to limit their activities outside.”
The current stretch of hot, humid weather lacking significant precipitation tends to push pollutants down to street level where the ozone hugs the ground. Pollutants can't dissipate at their normal rate, Poister said, which generally leads to higher ground-level pollution. In Pittsburgh, those conditions could extend into September, he said.
So what do we do?
Poister asks residents to set their thermostats higher, keep lights and appliances off when not in use and use carpooling or public transportation when going out. Car exhaust is a chief component for ground-level ozone, he said.
Without sufficient long-term change, he said, these elevated threat levels could extend deeper into fall.
