Hazy answers: Researcher studies risks, benefits of exercising in smoke

Anyone who lives in the fire-prone West has seen them: stubborn runners, bikers and hikers still exercising outside after wildfire smoke smothers the land in apocalyptic gray. They might cover their mouths with a bandana or filtered mask, but they refuse to let air alerts disrupt their health routines.

Exercise is good for you, but are these smoke-breathers doing more harm than good?

Enter John Quindry, one of those fit, stubborn people. Quindry sometimes can be spotted biking in sketchy air to work at the University of Montana, where he is a researcher, professor and chair of the School of Integrative Physiology and Athletic Training. Quindry and the other researchers in his school are known nationally for funded research in environmental physiology and rank among the best in the world for studying effects of smoke on human health.

With that pedigree, one would expect Quindry to rattle off quick answers about exercising in smoke. But the truth is he knows too much about the topic to be boxed into easy answers that lack nuance. He has worked on scores of studies, and for him the science isn't settled. But he will say this:

"Clearly people should exercise. Even a few times a week has huge benefits. And if people go to their annual checkup, and they are doing well, there is probably no reason for concern from most smoke we get here in Montana. The body is resilient, especially for those below age 60. But if you are in the smoke and become symptomatic – you find yourself wheezing or spots appear before your eyes – take note, back it off and talk to your doctor."

Quindry is particularly interested in smoke particulate matter smaller than 2.5 micrometers in diameter, known as PM2.5 in scientific communities. PM2.5 is tiny enough to reach the deepest recesses of our lungs, where thin-walled lung sacs line up with blood capillaries to take in oxygen and expel carbon dioxide. This exchange-area membrane is delicate and vital. If PM2.5 particles slip past the mucus in our lungs and then evade immune cells in our blood, they can cause damage such as cardiovascular aging.

Quindry and his partners have measured the biochemistry and physiology on both sides of that membrane since he arrived at UM eight years ago. And the first five or six studies found the body to be highly resilient when exercising in smoke – especially with young people.

However, science has shown that wildland firefighters after a full career may have a cardiovascular system that has aged 10 to 20 years beyond a person who didn't do such smoky work. The same is true of construction workers or farmers working frequently in PM2.5 haze. But UM scientists haven't replicated this in the short-term studies they have conducted.

"In a sense this is heartening," Quindry deadpans. "Maybe we aren't heading toward an early death as we live and breathe and exercise in Missoula."

However, their work has discovered something new. About 10% to 15% of people are genetically predisposed to have their blood pressure spike if they put one of their hands in ice water for two minutes. This quirky fact about hyperreactive blood pressure has been known for decades. These people are more likely to experience early onset hypertension and have heart attacks later in life. Quindry said their research found exercising in smoke was harder on these folks than others.

"When we separated out those subjects and had them exercise in smoke, we found they had a disproportionate response, and this is with subjects with an average age of 24," he said. "I don't know if we should start testing for this trait – with buckets of ice water and putting blood-pressure cuffs on people at the mall – but it is interesting."

In grad school, he read studies about there being more heart attacks in Midwestern places like Detroit after a weekend of wet heavy snow.

"It hasn't been proved scientifically yet," Quindry said, "but we suspect a lot of those people who have heart attacks from shoveling also would have their blood pressure spike after putting their hands in a bucket of ice water."

When studying the effects of smoke on people, Quindry often uses a newly defined metric, "PM MET minutes," as a tool to define individual exposure to environmental smoke.

MET means metabolic equivalent, and it describes the work to do anything in life. When we sleep, it's 1 MET. Being awake, watching TV and walking around is 1.1 to 3 METs. Three to 6 METs is activity that could include exercise. Above 10 METs is intense exercise, and the Lance Armstrongs of the world can hit 23 METs climbing the Alps in the Tour de France.

"The good news for the average schmo like me, is if I just hit 10 METs once or twice a week, you get all the exercise benefits you need to live a long and healthy life," he said. "You get most of the benefits just hitting 6 METs, and there are diminishing returns from 6 to 10. Above 10 METs you become a better athlete, but you don't actually live any longer on average than the rest of the population."

So a PM MET minute is the particle count in the air, multiplied by amount of time you are in it, multiplied by the METs (work) you are doing. For a wildland firefighter working a full day in PM 250 (which was the top count during Missoula's robust 2017 Lolo Peak Fire), the PM MET minutes come in at about 200,000. Quindry said that's a number they try to approximate with human subjects in the lab.

Quindry has garnered about $3 million in funding since he arrived at UM, studying the effects of prolonged smoke exposure on essential workers.

The application of these findings extends to all types of people with physically active jobs, including military personnel, firefighters, farmers and postal workers. To simulate those working conditions with human subjects, he sets the PM at a smoky level and makes subjects exercise rigorously for 45 to 120 minutes in UM's Air Inhalation Facility. The smoke dose is regulated by how big and frequently breaths are taken, and he uses METs as a surrogate for that dose. (And if someone really gets into METs, Quindry is co-author of a text called "Exercise Physiology," which has METs for everything from calisthenics to gardening neatly ordered in an eight-page appendix.)

He said the PM MET minute threshold of 200,000 is what they have documented scientifically so far, and their subjects seem to handle that level fairly well. However, people who experienced the 2017 Rice Ridge Fire near Seeley Lake lived in PM spikes of PM2.5 counts up to 900 at times.

"In the short term, we don't know what that sort of exposure does to people," he said. "That's off the charts into unexplored territory based on what modern science has explored."

So we still don't fully understand the long-term effects of exercising in smoke. But Quindry, the smoke-health expert, is an avid biker who never "goes hard" when the PM count is above 50. (For him, "hard" is biking 3,000 feet up a mountain.) He will keep biking to work outside even if the PM count rises to 75, but he would move more strenuous exercise inside.

"You have to trust your common sense," he said. "For the kinds of activity and exercise that most of us are going to do outside, we haven't discovered anything that turns that on its ear and should scare you off too much. And, actually, that's pretty good news."

Provided by University of Montana