Shifting winds are sending smoke our way. What’s that mean?
10 questions for atmospheric chemist Richard E. Peltier
The Bay Area Air Quality Management District is issuing an air quality advisory for smoke on Friday through Sunday, August 19. Polluted winds are expected to head our way, blowing smoke from fires in northern California, eastern Washington and British Columbia. That’s in addition to Friday’s “Spare the Air” alert for car-caused smog — the seventh this year.
What’s the problem? We asked atmospheric chemist Richard E. Peltier, associate professor of Environmental Health Sciences at the University of Massachusetts in Amherst, who studies wildfire smoke.
Q
What is inside wildfire smoke?
A
It changes. It depends on what things are burning. Broadly, it is a mix of both particulate droplets and gases from burned trees, dried leaves, forest litter and, unfortunately, homes. And these particles and gases interact and change over time, as they travel downwind. Wood smoke is a complicated mixture and there’s no one answer.
Q
Why is it dangerous?
A
Generally, it is pretty toxic and can make you sick. There is carbon monoxide, the gas that comes out of the car. There are organic carbon compounds. There is a huge mixture of gases — 5,000 to 10,000 different gases — including polycyclic aromatic hydrocarbons, some of which are known to
cause cancers.
Q
What does research tell us about the types of smoke exposure we’re now seeing in California?
A
Research is hard to do on this subject. Everything we know about smoke comes from controlled labs, where you add a specific kind of smoke to a room and certain populations of people breathe it. We know what it looks like in that controlled condition.
And we know what generally happens to people who are exposed to it on their job, or who participate in prescribed burnings.
What we don’t know much about are general populations with upwind exposure, like you’re seeing now in California. The research all suggests that it’s pretty nasty. But it doesn’t mean you’re going to get sick. It means you’re at elevated risk.
We all wear seat belts when we drive in a car, because there’s a low chance we’ll be in an accident. If you’re a dangerous driver, that risk goes up.
It’s the same with smoke — there’s always a small risk that there will be some kind of health effect. When you increase the smoke, you increase that risk.
Q
Is a weekend of exposure considered dangerous?
A
That depends on two things.
It generally does have an effect on susceptible people — the elderly or children, or people who are sick with cardiovascular disease or asthma. Those risks go up even with just a weekend of exposure.
It also depends on distance. We generally see plumes of polluted clouds. The pollution lowers in concentration the further it goes, because it becomes more dilute.
Q
So the risk is reduced if you’re farther away?
A
The absolute concentration of toxins from 500 miles away is going to be lower than five miles
away. In the summertime, those big hot plumes might eject smoke up to the higher altitudes — 1,000 or 2,000 meters.
But when that plume of pollution travels over 500 miles, it might expose 5 million people.
It also depends where you are — in mountainous areas, where the atmosphere is capped, the pollution can stick around.
Ultimately, all wood smoke lands on the ground.
Q
The conventional wisdom is: If you smell smoke, you’re breathing it. But if you can’t smell it, you’re OK. Is that true?
A
Yes and no.
Many chemicals, when they burn, have no odor — like toxic carbon monoxide. But the smelly stuff comes hand-in-hand with carbon monoxide. So there’s truth that if you smell it, your lungs are exposed to it.
But if you can’t smell it, that doesn’t mean you’re not exposed. Everybody is different at detecting certain odors. Maybe you have nasal congestion. Maybe you tend to breath through your mouth, not your nose.
Q
In some parts of California, our air pollution has been compared to Beijing, one of the world’s most polluted cities. Is that a fair comparison?
A
People lump air pollution into a single evil thing. They say: ‘Air pollution is high.’ Or: ‘Air pollution is low.’
But air pollution is made up of all kinds of different compounds. And there are different groups of different compounds, depending on whether the pollution is from cars, forest fires or something else.
In places like Beijing, there’s a wider mixture of things. There’s ozone, carbon molecules, SO2, plus lots of particulate matter. It is a mixture of gas and diesel and coal smoke and many other things. It is soupier.
When we talk about relative risk, we really don’t know if what’s going on in California is equivalent, on a per unit basis, to what you might see in Beijing. In Beijing, high concentrations are sustained across the entire region for days or even weeks.
But the evidence would suggest that at least some Californians are experienced what it is like to live in a developing country without strong air pollution controls, like Beijing.
Q
When the air is smoky, what is the best way to protect yourself?
A
When you have a fire event in your town, removing yourself from it, for the short term, is the best. But that is not practical for a lot of people who have jobs and families and school.
Coming indoors, and closing windows and doors, is helpful. If you have an air conditioner with a good filter, that would be helpful as well. Try to seal away the pollution.
Q
What devices do you recommend?
A
Portable high-efficiency filter devices — HEPA devices — are useful for cleaning the air, but only only for a small room. They’re not designed to clean air in an entire house. Put it in a place where you spend the most time. That’s usually the bedroom, because you’re sleeping.
If you need to be outside, using an N95 face mask can be useful. It doesn’t cost a whole lot of money and it removes particulate matter.
Air fresheners are ineffective. They don’t remove the pollution — they just make it smell nice. They are not recommended.
Q
Should we worry about our firefighters? A
Firefighters — they’re a special class of superhuman. But when they’re fighting a fire, it’s important that they take as many breaks as they can — in locations that are upwind, with fresher air. It’s important that they take a ‘precautionary approach,’ taking care of themselves with nutrition and hydration, because the smoke will affect their lungs. It causes inflammation. They’re at increased risk of lung and cardiovascular diseases.