Health Effects of Wildfire Smoke and Ash: Lessons From California

Robert Glatter, MD: Hello. I'm Dr Robert Glatter, assistant professor of emergency medicine at Northwell Health and attending physician at Lenox Hill Hospital in New York City.

The year 2017 was particularly devastating for California. The October wildfires in Northern California killed at least 44 people and caused unprecedented levels of air pollution.^[1]

The Thomas Fire in Southern California has become the largest in the state's history.^[2] The smoke and ash from these fires exposed the population to the risk of inhaling particulate matter, sending many people to the emergency department. Now, as the latest blaze gradually comes under control, it's important to contemplate the health effects of wildfire smoke exposure.

Here to talk to us today about this topic is Dr John Balmes, professor of medicine at University of California-San Francisco and attending physician in the divisions of pulmonary and critical care medicine at Zuckerberg San Francisco General Hospital. I want to talk about the acute effects as well as long-term effects of smoke, especially from fires, and how this affects respiratory and cardiac health.

John R. Balmes, MD, MPH: Particulate matter is the primary constituent of wildfire smoke that we are concerned about in terms of health effects. There are many other nasty chemicals in wildfire smoke, but the bulk of the problem is related to particulate matter. Particulate matter comes in different sizes, and it's the fine particulate matter that can make it deep down into the lungs, which is what the Environmental Protection Agency (EPA) regulates and what we're concerned about.

Dr Glatter: There are different sizes, from 2.5 microns up to 10 microns. Is the 2.5-micron size the one that's causing the inflammation we see in lungs?

Dr Balmes: Yes. "PM10" means the particles are 10 microns in diameter or less. They make it through the vocal cords and into the large airways, so those particles can exacerbate asthma and chronic obstructive pulmonary disease (COPD). The small particles (2.5 microns; PM2.5) can make it down to the deep lung. Those are the ones that have been associated with an increased risk for death due to both respiratory and cardiovascular problems.

Dr Glatter: If an average person is exposed to smoke—for example, with this recent fire—and is overcome by the smoke, what is the impact of that exposure in and of itself? Is that enough to cause an inflammatory response or lead to some cardiac or respiratory issue down the line?

Dr Balmes: It all depends on the dose, like almost anything in medicine. If someone is near the fire, then the exposure is very heavy and they can actually be overcome with carbon monoxide intoxication. There was a woman who died in her husband's arms in the Santa Rosa fire. They sought shelter in a swimming pool. The husband made it; the wife didn't.

Farther away from the smoke, downwind in the Central Bay area—for example, during the October fires—the levels were quite high, as you mentioned. Unprecedented. The highest recorded in the Bay area. Most people had some eye, nose, or throat irritation, but the people most affected by those levels were those with preexisting heart or lung disease.

Dr Glatter: People with longstanding asthma or COPD—these are the patients who come to the emergency department and whom we see acutely. Can we expect any longer-term effects other than the pulmonary effects? In other words, any cardiac effects? Could you speak to that?

Dr Balmes: PM2.5 comes from different sources. Most of the PM2.5 that we experience without wildfires comes from combustion sources, such as motor vehicle emissions and power plants. That PM2.5 is associated with exacerbations of preexisting heart disease and death due to cardiovascular disease, either myocardial infarctions or strokes. It's not as clear that wildfire smoke, which is from wood combustion, is as toxic cardiovascular-wise. Respiratory-wise, there is no question. But cardiovascular effects of wildfire smoke are a little bit murky.

Dr Glatter: In a sense, does the smoke trigger inflammation that accelerates atherosclerosis? Has that been established?

Dr Balmes: With other types of PM2.5, definitely. There are some animal data in regard to wood smoke, but the epidemiology of human population studies is conflicting in regard to wildfire smoke and cardiovascular disease. I give advice to the public saying that we should be precautionary. People with heart disease need to protect themselves during these wildfire smoke episodes.

Dr Glatter: How can the general public and patients with lung or heart disease protect themselves? What is your advice on the important things to do in case of a fire?

Dr Balmes: Even healthy people should avoid exercising outside when the smoke is heavy. People with asthma, COPD, or heart disease should try to stay indoors, keep the windows closed, and turn off ventilation systems that bring in outside air without filtration.

If they have filter systems, then make sure they are high-efficiency particulate air (HEPA) filters. If they have to go outside, wear an N95 or N100 mask, which are the kind of masks we wear in hospitals to protect us from occupational transmission of tuberculosis. Those masks are available in hardware stores, home building stores, and pharmacies.

Dr Glatter: In terms of smoke cleanup, can you advise a safe way to help dispose of ash? Is there a specific way to go about this?

Dr Balmes: That's tricky.

In the Santa Rosa area after the October fires, there was a lot of ash in the neighborhoods—Coffey Park, in particular. That ash is actually probably more toxic than regular wildfire ash because that was a neighborhood that burned, so there were synthetic materials in the homes and cars—so there were more metal oxides and synthetic products of combustion.

The workers who clean up that ash have to be properly protected with N95 masks. People entering their homes should be wearing N95 masks. They shouldn't be vacuuming without special vacuums with HEPA filters. Wherever possible, they should wet the ash down with clean up. The bottom line is that using professionals is the best way to clean up after a fire—people who are trained properly.

Dr Glatter: You focused on the point of using water to clean up ash because of the risk of spreading the ash if you improperly use a vacuum. That could put people at risk.

Dr Balmes: The other thing that people can do—and I think the American Lung Association actually distributed some of these—is to get a good stand-alone home filtration device. There are several reputable brands. They should have that running at all times when they are trying to clean up. And if possible, have more than one in a home.

Dr Glatter: In a general sense, how long after exposure to fire smoke can health effects appear? Are we looking at 5 years or 10 years? Can you speculate on that?

Dr Balmes: Fortunately, while the exposures are heavy, they usually last for only a few days, so we mostly worry about acute, and not long-term, effects.

The people in whom we have to worry about long-term effects are the firefighters, especially wildland firefighters, because they can't wear the self-contained breathing apparatus that structural, urban firefighters wear. They are on the fire line for a long time—12-hour shifts and many days in a row, and they do it over the entire fire season. Some of them do it for years at a time.

The National Institute for Occupational Safety and Health is actually instituting a long-term study primarily to see whether there is increased risk for cardiovascular disease, COPD, and even cancer in these workers.

People who are exposed, even if heavily exposed, to one of these California wildfires are not likely to have long-term effects. There isn't enough exposure to chronically affect heart or lung disease and certainly not enough to cause cancer. However, there are some exceptions. Somebody with asthma could have a permanent worsening of their asthma with heavy exposure, because they get so much inflammation in their airways that it basically moves their asthma into a worse state.

Dr Glatter: Can you estimate the amount of carbon dioxide that was released as a result of this blaze? Have there been any data indicating that?

Dr Balmes: I think people have looked at this. I'm not going to be able to quote numbers, but as you alluded to earlier in the conversation, the amount of carbon dioxide that's emitted is a lot. It almost, in some ways, wipes out all of the efforts we've been making in California to have clean energy and clean vehicles, to have these catastrophic wildfires.

Dr Glatter: That brings us back to the point about climate change and doing all we can. These fires are devastating and certainly compound our efforts to help combat the situation.

Dr Balmes: Governor Brown said it well, after a few days of the Thomas Fire. He said that this is the new norm for us, and that we have to do all that we can to both try to better prepare communities for these catastrophic fires, but also to double our efforts in regard to climate change. And he's right.

Dr Glatter: Controlling fires is part of climate change now. I want to thank you for your time. This has been very beneficial. The fires have affected so many people in California, and to put this into perspective has been immensely beneficial. Thank you again. I appreciate your time.

Dr Balmes: Thank you.

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