You may have noticed what looked like small snowflakes drifting down from the sky in western Montana on Monday, but they were actually bits of ash that traveled from California, Washington and Oregon fires all the way to the Missoula valley.

Missoula City County Health Department Air Quality Specialist Sarah Coefield has been tracking the smoke since the fires began.

We’re most concerned about the size of the particles though they are so tiny that when you breathe them in, they can bypass your natural defenses and go deep into your lung and can actually pass into your bloodstream.

“It started building up yesterday,” said Coefield. “I'm sure people noticed that they couldn't see the sky yesterday and as the inversion finally broke late yesterday afternoon that smoke mixed down to the ground and conditions actually continued to deteriorate overnight. Starting about four o'clock yesterday afternoon it kind of got worse and worse and worse and worse, and here we are this morning in unhealthy air quality throughout Missoula County.”

Coefield has been studying the particulate from wildfire smoke for years, and describes how damaging it can be to the human body.

“We’re most concerned about the size of the particles though they are so tiny that when you breathe them in, they can bypass your natural defenses and go deep into your lung and can actually pass into your bloodstream,” she said. "There they set off an inflammatory response which really is why you start to feel really crummy when it gets smoky outside, because your body is trying to fight this stuff that isn't supposed to be in it.”

Coefield is particularly concerned about the damage to those whose health is already compromised.

“For folks that have pre existing conditions such as heart or lung disease, that particulate matter can be very, very harmful,” she said. “We see increased frequency and severity of asthma attacks. We're seeing symptoms of COPD, and there's increased risk of heart attack and stroke. When you have a smoke event in a population, you typically will see increased mortality, and increased hospital visits for pneumonia and other infectious diseases.”

She said other parts of the state have even worse air quality due to the smoke.

“The worst air quality is currently in Libby where air quality is hazardous, and it’s very unhealthy in Thompson Falls,” she said. “As you go eastward, it starts to improve quite a bit. Most of the smoke is kind of hung up west of the Continental Divide, so once you get past the divide, it gets better. Then certainly the further west you go across the country, the worse it gets until you get on the other side of the smoke closer to the coast where the wind is going to finally start pushing that smoke inland and the folks on the coast are going to hopefully finally have some good air to breathe after days of some of the worst air we've seen in a long time.”

Click this link to get the current air quality report from the Missoula City County Health Department.