The plume is packed full of carbon dioxide and carbon monoxide, methane and benzene, hydrocarbons, nitrogen oxide, sulfur dioxide, ammonia, oxygenated compounds and chlorinated compounds.
So health concerns are understandable whenever firefighters become fire breathers. How much wildfire smoke can the lungs handle, and for how long?
In fact, cancer risk from a dental X-ray is about seven per million, he said. Cancer risk from working on a Type 2 fire crew is about half that, 3.2 per million.
By comparison, a two-pack-a-day smoking habit comes with a cancer risk estimated at about 100,000 per million.
That's according to a report written by Sharkey, titled “Health Hazards of Smoke,” and released by the Missoula Technology Development Center, a U.S. Forest Service facility where staff conducts field studies into firefighter health, among other things.
Sharkey works there as both a physiologist and project leader; before that, he was professor of exercise physiology at the University of Montana, where he studied firefighter safety from 1964 until his retirement in 1997.
“The public health message is ‘smoke is dangerous; don't go out,' ” Sharkey said. But for a healthy person, he said, the danger is slim to none, even on the fireline.
Turns out, the human body is well adapted to handle the amount of fine particulate that can cloud skies during the summer fire season. Cilia - tiny hairlike projections - easily sweep the particulate up and out of respiratory passages.
Sure, too much smoke can deaden the cilia action and suppress the immune system. That allows particulate to build up, and can eventually lead to bronchitis.
But such a system failure requires fairly long-term exposure to fairly high levels of smoke pollutants, which is generally not the case around wildfires.
Take away the smoke come autumn, and the cilia bounce right back, healthy as ever.
Studies of firefighters have shown a short-term decrease, ever so slight, in lung function on heavy smoke days. But crew members were back to normal in a matter of weeks.
Similar studies of Missoula's third-, fourth- and fifth-graders showed similar decreases - and similar returns to normalcy - within eight weeks of fire season.
Clear the air, Sharkey said, and you clear the temporary problems of cough and shortness of breath.
In addition, those slight decreases in lung function often are not even felt by a system engineered to handle much worse.
“The respiratory system is overbuilt for its duties,” according to the report. “Its capacity is one-and-one-half times that needed at maximal effort.”
A slight and temporary decline in lung function, the report concludes, “is not noticeable and it does not decrease work performance. The human lung has a remarkable capacity to cleanse itself when given an opportunity. In one study, decreased lung function persisted 16 days - but not 25 days - after exposure to smoke.”
In other words, you're much worse off living in urban smog 365 days of the year than you are working on a fireline or living under seasonally smoky skies.
Back in 1998, the National Institute for Occupational Safety and Health joined several fire management agencies to evaluate carbon monoxide exposure among four firefighting crews.
“The data,” Sharkey reports, “did not exceed recommended limits for time-weighted average exposure to carbon monoxide.”
And that's for people working and breathing in the thick of it.
Firefighters certainly take in more smoke than community members, on average, but “a four-year study showed that wildland firefighters have above-average lung function and that occupational exposure to smoke has little effect on the decline in lung function that normally occurs with age.”
“The risk,” Sharkey concludes, “just isn't what it's been made out to be.”
Still, independent studies in 1989, 1994 and 2000 show 30 to 50 percent of firefighter visits to medical tents are for upper respiratory problems, including coughs, colds and sore throats. Changes have been made to firefighting efforts - particularly during mop-up - to keep crews out of the heaviest smoke.
But researchers know those sorts of upper respiratory ailments have several roots, including fatigue, stress, smoke, sleep deprivation and poor nutrition.
“A healthy immune system is the best protection against the effects of smoke,” according to Sharkey's report. “Immune function is enhanced with regular moderate physical activity, good nutrition, hydration and adequate rest.”
The physiologist notes that's good advice no matter the air quality.
And while you're eating right and exercising, you might want to kick that habit, as well.
“Firefighters who smoke have more carbon monoxide in their blood on the way to the fire than do non-smoking firefighters at the end of the work shift,” the document reports.
Likewise, while there's ample evidence than smoking tobacco can cause cancer, the World Health Organization says there's been no conclusive link made between seasonal wildfire smoke and cancer.
“An assessment of chronic smoke exposure for wildland firefighters indicated little increased risk for the average firefighter, even though exposure can be several times higher than that experienced by residents of communities exposed to smoke,” the report states.
And while wildfire smoke may be a potential carcinogen, “it is much less of a cancer risk than motor vehicle exhaust or other known carcinogens.”
So your eyes may burn, Sharkey said, your throat may scratch and your head may ache a bit - especially if you're older or younger or asthmatic or allergic - but the risks of long-term trouble are remarkably slight, even for firefighters with their noses in the ash.
His report quotes from an Aug. 23, 2000, letter from the Montana state medical officer to public health officials:
“Although the impact of the poor air quality is quite serious for those with underlying heart and lung disease, this is not true for healthier individuals. There is no doubt that the smoke is irritating and results in scratchy throats, dry coughs, irritated sinuses, headaches and rhinorrhea. However, these effects are not permanent.”
Nor, he says, are they overly serious.
“The risks of occasional exposure to fine particulate and other components of vegetative smoke,” the report concludes, “are minimal for healthy individuals.”
Irritating, it is. Life threatening, probably not.
“Everybody thinks, ‘Oh, it's a terrible problem,' ” Sharkey said. “And part of the reason for that is the public health message. But we need to be honest and realistic about the risks here. The evidence suggests it's just not that bad.”
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