Thick smoke from wildfires ringing Southern Oregon caused Medford's air quality to drop to unhealthy levels late Monday afternoon, with enough particulates in the air to cause health problems for residents.
The air-quality index in Medford ballooned Monday afternoon to 164 for particulate matter, with indexes of 150 to 200 considered poor enough that everyone could begin experiencing health effects, according to the state Department of Environmental Quality.
At that level, sensitive groups such as children, elderly or those with respiratory problems may experience more serious health effects, according to the DEQ.
Levels under 50 are considered good air-quality, with poor quality starting with an index of 100. "Very unhealthy" conditions occur at an index above 200 and hazardous conditions begin at an index above 300.
Josephine County communities of Provolt and Cave Junction on Monday were suffering with hazardous levels of particulate matter that were more than twice those in Medford. The air quality there was poor enough to potentially to cause serious health effects even for healthy people, according to the DEQ.
In the 6 p.m. reading, Cave Junction recorded an air quality index of 345 with Provolt's at 343.
Conversely, the station in Talent measured good air quality Monday evening, according to the DEQ.
Grants Pass, however, came in Monday evening at 131, high enough to be unhealthy for sentitive groups.
The Rogue Valley's air deteriorated rapidly Monday when winds not only blew in the smoke from low elevations but also carried in parts of the thick plume of smoke that normally rises vertically from wildfires, according to the National Weather Service in Medford.
As the day heats up, thermals push smoke down over the valley floor instead of up and over the mountains ringing it, said meteorologist Sven Nelaimischkies.
"That's mixing the smoke down into the valley," Nelaimischkies said Monday. "The winds are blowing everything into us. We have 21/2; miles of visibility. It's made our air crap."
Smoke levels could abate somewhat today as wind patterns shift and blow smoke from Oregon's fires north and west, he said.
"We'll still get the low-level smoke, but it won't mix as much of that upward smoke down," Nelaimischkies said.
William Knight, a spokesman for the DEQ, said the hazardous air ratings are based on a nationwide standard for particulates in the air.
"Folks need to really think seriously about taking some additional measure to protect themselves from the smoke: staying indoors, avoiding contact as much as possible, so they're not ingesting all the harmful pollution at unsafe levels," Knight said.
An online map to determine the air quality in different parts of the state is available at the DEQ website at www.deq.state.or.us/aqi/index.aspx.
Fire incident updates are available at www.inciweb.org.
Get updates on Oregon smoke levels from multiple agencies at http://oregonsmoke.blogspot.com.
Reach reporter Mark Freeman at 541-776-4470, or email at email@example.com.