It's no secret that there hasn't been much "quality" to southwest Oregon air for the past few weeks, thanks to the numerous smoke-churning wildfires burning across the state.

But data from the Oregon Department of Environmental Quality shows just how bad it's gotten. Most of the six air-quality monitoring stations scattered across Jackson and Josephine counties have not registered "good" air quality since Aug. 13, and several show a gradual, worsening decline.

Medford, for example, saw air quality diminish from "good" on Aug. 13 to "moderate" through Aug. 19, based on historical 24-hour totals recorded by the DEQ's website. It then degraded further to "unhealthy for sensitive groups," then "unhealthy" Aug. 20-23. It saw a short-lived bounce back to "moderate" Aug. 24-25, then slipped back into poor ranges. Seven of the 11 days between Aug. 26 and Sept. 5 were "unhealthy," and two were "unhealthy for sensitive groups." Sunday and Tuesday this week saw the first drop into "very unhealthy" levels.

Then came today: As of noon, Ashland and Medford both registered "hazardous" for the past 24 hours.

The main health issue from so much smoke comes from the lilliputian specks of pollution that drift with it. Fine particulate matter, also referred to as "particle pollution" by the Environmental Protection Agency, is broken into two categories, PM 10 and PM 2.5. The numbers refer to the particle's size, with PM 10 referring to particles that are 10 micrometers or small, and PM 2.5 referring to particles that are 2.5 micrometers and smaller. For comparison's sake, a human hair is 50 to 70 micrometers, while a grain of sand is about 90.

The particles can burrow deep into the lungs and result in a spate of health problems from prolonged exposure, including asthma aggravation, decreased lung function, irregular heartbeat and "nonfatal heart attacks," according to the EPA website.

"Inhaling particulate matter is a leading risk factor for premature death," said Greg Svelund, Oregon DEQ spokesman. "For people with heart and lung disease, this is a pretty serious thing."

Area air stations monitor the number of particles in the air with laser technology, Svelund said. Samples get pulled into a tube, and lasers shine across it. The beams scatter when they come across the particles, so the more scattering, the more particles are present in the sample.

"That correlates really well with the concentration," Svelund said.

Wearing certified masks, specifically the N95 and P100 models, can help, though health officials recommend staying inside as much as possible. Those with cabin fever can certainly head to other indoor locales.

"Go to the library, go to the mall, watch a movie," Svelund said.

Staying hydrated and not pushing yourself physically are also important.

The smoke is probably here to stay for a bit. Some slight improvement is forecast later this week because of chances for rain, though no actual clearing is expected, according to National Weather Service meteorologist Misty Firmin. But even with that, there's a chance the haze will just thicken right back up. And new fire starts from possible lightning strikes could worsen it.

"It’s going to depend on how the next few days go out with all the thunderstorms," Firmin said.

The Chetco Bar fire, burning on old burn scars in the Kalmiopsis Wilderness, remains the largest fire in the state. On Wednesday, it had grown to 176,770 acres, with fire officials halving an earlier containment percentage from 10 to 5 percent. There are nearly 1,700 personnel assigned to the fire, and evacuation notices remain in effect for remote areas of Josephine and Curry counties. An updated interactive map on current evacuation levels across the fire area can be viewed at https://goo.gl/keU1PZ.

The High Cascades Complex, made up of 20 fires burning near Crater Lake, is at 18 percent containment and is 52,255 acres in size. The Miller Complex, which includes multiple fires in the Applegate east of Cave Junction, is 25 percent contained and is 28,670 acres in size.

— Reach reporter Ryan Pfeil at 541-776-4468 or rpfeil@mailtribune.com. Follow him at www.twitter.com/ryanpfeil.