Why is wildfire smoke bad for you?

Wildfire smoke includes tiny pieces of material called particulate matter (PM). A type of PM called PM2.5 is particularly worrisome because it is so tiny — less than 2.5 micrometers (30 times smaller than the diameter of one strand of human hair).

“The reason we talk about PM2.5 is that it can actually get deep into your lungs,” Dr. Altman says. “You have many layers of protection, for example, mucus and cilia (which are like very small hairs), to keep things out of your lungs. But these tiny particles can get past our defenses.”

When these particulates get into your lungs, they can cause a variety of health problems. Some of these can be short-term, like throat and lung irritation, coughing and sneezing. The particulates can also exacerbate existing respiratory conditions like asthma and can contribute to heart disease. Long-term exposure to PM2.5 is linked with several serious health issues like bronchitis and reduced lung function.

What is the air quality index (AQI)? How do you know if the air in your region is safe?

In regions where wildfire smoke is common, people will often read the air quality index (AQI) to understand the air quality in their area, and to assess their health risks. AQI measures pollutants in the air on a scale that includes:

• Good: 0-50, little to no pollution risk
• Moderate: 51-100, air quality is acceptable, very low risk
• Unhealthy for sensitive groups: 101-150, members of sensitive groups may experience health effects
• Unhealthy: 151-200, the general public may experience health effects, sensitive groups may experience more serious health effects
• Very Unhealthy: 201-300, increased health risk for everyone
• Hazardous: 301 and above, emergency health warning, everyone is more likely to be affected

“Sensitive groups” typically include people with conditions that impact their respiratory system including asthma, chronic obstructive pulmonary disease (COPD), and other lung and heart diseases.

“It's not a hard cutoff, it’s not that 199 is safe and 201 is not,” Dr. Altman says. “But generally, the higher the AQI gets, the more people are going to experience both short and long-term health effects.”

How does wildfire smoke impact people with asthma? Can wildfire smoke make asthma worse?

“The short answer is yes, wildfire smoke makes asthma worse,” Dr. Altman says. “The longer answer is that there’s less research around how pollutants like smoke trigger asthma than there is for other causes like allergens and viruses.”

Scientists learned that pollution impacts asthma by looking at epidemiologic data in places like Los Angeles, with high levels of PM2.5 and other pollutants.

“This epidemiological data looks at thousands and thousands of patients and shows spikes of asthma attacks correlated with pollution including from wildfires,” Dr. Altman says. “However, it basically only tells us that those patients needed medical care for their asthma, not how wildfire smoke causes asthma attacks.”

Dr. Altman and his colleagues are digging deeper, by doing research that aims to uncover key details about the relationship between smoke and asthma.

“We’re taking a deeper look at several hundred patients, getting samples from their blood and airways to learn more about exactly what’s going on in the immune system when air pollution triggers asthma,” he says.  

One challenge is that wildfire smoke is a complicated mix of various pollutants.

“So, unlike a virus where you can just study one virus or allergens where it's one specific thing, we’re looking at a mix of particles, volatile gases and other things within wildfire smoke and are trying to understand what the body is reacting to and how it is reacting,” he says.

This research could have important implications for how asthma induced by smoke is treated.

“Right now, we’re seeing that asthma attacks caused by pollutants use a different mechanism than those caused by a virus or allergen,” Dr. Altman says. “That means that conventional asthma drugs may not work as well for this type of asthma attack. Future studies will likely look at treatments that are more targeted for smoke-induced asthma attacks.”

What can you do to protect yourself from wildfire smoke?

The CDC recommends the following measures to help reduce the effects of wildfire smoke:

• Stay inside with windows and doors closed as much as possible. HEPA air filters can help improve air quality in your home. Run air conditioners if you have them. If you do not have an air conditioner, look for local shelters or cooling stations in your area.
• If you do need to go outside, avoid strenuous exercise.
• Avoid activities that increase pollution like smoking, frying foods and using fireplaces or gas stoves in your home.
• Help prevent wildfires by following local regulations for campfires and burning trash and debris.