Update Friday 4:30 p.m.
A Code Orange Air Quality Alert has been extended through Saturday for the Knoxville area, Great Smoky Mountains National Park and Chattanooga.
More fires have broken out in the region and pollution levels are rising, the Tennessee Department of Environment and Conservation said in issuing the air quality alert.
A rain front coming through the area Friday night and Saturday is not expected to bring much precipitation, the department said.
A Code Orange alert means atmosphere levels are "unhealthy for sensitive groups." The general public isn't expected to be affected; however, those with lung diseases, older adults and children are at a greater risk from exposure to ozone.
In these alerts, members of "sensitive groups" should consider limiting or rescheduling strenuous outdoor activities until the air quality improves.
Crews have been battling dozens of wildfires across the state for several days with most of them located in the East Tennessee area.
The region has spent most of the week under some level of air quality alert. The state initially did not issue an alert for Thursday, but did issue one Thursday afternoon.
Previous story Thursday 7 a.m.
With smoke levels decreasing in the atmosphere, the state will not issue an air quality alert for East Tennessee for Thursday.
The Environmental Protection Agency forecasts Knoxville's air quality in the Code Yellow or moderate zone, which means there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
We were at a Code Red Alert on Wednesday, because of high levels of ozone in the air that is unhealthy for all of us to breathe.
The state's Department of Environment and Conservation's Division of Air Pollution Control monitors the conditions and issues the alert. If levels start increasing again, they could choose to issue an alert at a later time.
While there will be no alert issued, the air quality could still be unhealthy in the areas nearest the dozens of wildfires that continue to burn in the area.
An Air Quality Alert remains in effect for all of East Tennessee through Wednesday, but it has now risen to a Code Red level.
The Tennessee Department of Environment and Conservation said Tuesday it is extending the alert to Wednesday in the Chattanooga, Knoxville, Great Smoky Mountains and Tri-Cities areas due to ongoing wildfires across the entire Southeastern United States. Those areas have been under a Code Orange alert Monday and Tuesday.
Nashville is under a Code Orange alert Wednesday.
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While a Code Orange Alert means ozone levels are expected to be at an air quality index (AQI) that's "unhealthy for sensitive groups," a Code Red Alert means the ozone levels are expected to be "unhealthy" for everyone.
"Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects," the alert said. It is recommended people reduce prolonged or heavy exertion outside.
The air quality alert comes from continued wildfires burning throughout the Southeast. Smoke from those fires are blowing over parts of East Tennessee, triggering the alerts. At times during this incident, parts of East Tennessee have seen a Code Red Alert, meaning everyone may be at risk of experience negative health impacts.
"The biggest health threat from smoke comes from fine particles," the alert said. "These microscopic particles can get into your eyes and respiratory system, where they can cause health problems such as burning eyes, runny nose and illnesses such as bronchitis. Fine particles also can aggravate chronic heart and lung diseases."
See the different levels of air quality alerts HERE.
Lynne Liddington is head of Knox County's Air Quality Management Division, within the county health department.
"We have not had strong wind or rain in quite some time," she said, which contributes to the air pollution.
Dry conditions help wildfires spread, while a lack of strong winds mean the air pollution hangs around - especially in the Knoxville area, which acts as a bowl between the Great Smoky Mountains and Cumberland Plateau.
In her 35 years with the Knox County Health Department, Liddington said, she's never seen air quality this poor for this long of a stretch.
"I've also never seen forest fires affecting us the way they are right now," she said.
On Monday afternoon, Brandon Kocent was at Sharps Ridge, taking photos of the view - or lack thereof.
"You can see the Smokies clearly," he said, describing the view under normal circumstances. "You can see downtown Knoxville, my neighborhood, and you can't see any of that today."
He said the pollution has been a topic of conversation at the restaurant where he works.
"Yeah, a lot of people that I work with are congested," he said. "A lot of people I deal with at the restaurant are congested."
Over-the-counter sanitary masks won't protect against pollution, Liddington said. That's because the air pollution particles are so small - about 1/13th the width of a strand of human hair, she said - they'll pass right through the mask.
Dr. Michael Miller is a Knoxville-area allergist. He said the best way for people to protect themselves and their loved ones from the pollution is to stay indoors, with the windows shut and air conditioning on. He recommends people use the air-recirculation feature in their car, so outdoor air isn't constantly flowing through the cabin.