The mucus and hairs in your nose can trap larger particles, and the mucus and cilia in your upper airways can trap some, too, said Luke Montrose, an environmental toxicologist at Colorado State University. But some particles that are PM2.5 or smaller can get around those defenses and penetrate the deeper parts of your lungs.
Dr. Montrose described the lungs as an upside-down tree: Smoke travels through the airways, the trunk. Smaller particles can reach the tips of the tree’s leaves, the alveoli. These air sacs deposit the oxygen from your breath into your bloodstream. When PM2.5 particles enter, they can impair lung function and cause irritation.
Even smaller smoke particles, one-thousandth the size of PM2.5 particles, can pass from your lungs into your bloodstream, potentially causing damage at the cellular level, said Carlos Gould, an environmental health scientist and assistant professor at the University of California, San Diego. That could explain some of the health effects researchers have linked to wildfire smoke, including heart disease, infertility and dementia.
People near a wildfire can also ingest particles that settle in drinking water or food. These particles are dangerous to consume because they can contain potentially carcinogenic substances like benzene. Skin and hair follicles can also absorb smoke, which can cause itching and skin irritation.
Unanswered questions
It is difficult to disentangle the link between health and smoke. There is enormous variation in the health status of individuals before exposure to smoke, in the amount of smoke they are exposed to, and in what is in that smoke.
Researchers are seeking to answer two of the biggest questions: How much time do you have to spend in smoky air to feel health effects? And how smoky does the air have to be for that to happen?
The Air Quality Index, which measures five pollutants on a scale of 0 to 500, is an indicator of wildfire smoke pollution. It is an indicator that measures the presence of five pollutants on a scale of 0 to 500. Generally, Air Quality Index levels above 100 are considered potentially unsafe for children, the elderly, and people with heart or lung disease, and levels above 200 are considered “very unhealthy” for everyone.
Researchers are just beginning to study the impact of different levels of air pollution on health by tracking wildfire survivors’ outcomes over time. After a 2017 fire, researchers at the University of Montana looked at community members who had been exposed to heavy smoke for six weeks and followed them for two years.
Over those six weeks, the average air quality index in the area was about 221. The researchers initially saw no change in the participants’ lung function. “But then over the next year, they started to see that lung function had declined,” Dr. Montrose said.
Research also suggests that these effects may be cumulative, meaning your risk may increase over time as you are more exposed. People who are frequently exposed to high levels of smoke, such as some firefighters, may develop serious problems. Their lung function may decline, and they may develop higher levels of inflammation. They may also have an increased risk of lung cancer.
Researchers don’t have data to determine whether it’s more harmful to experience high levels of smoke for a short period of time or low levels for a long period of time, but they are certain: As the number of smoky days in the United States increases, many Americans will be at increased risk because smoke affects them year after year.
“We’ve moved from looking at daily and weekly exposures to looking at annual or multi-year exposures because now there are communities that are chronically exposed,” said Stephanie Cleland, an environmental health scientist and assistant professor at Simon Fraser University.
How to protect yourself
If smoke is in the air, try to stay indoors with the windows closed, she added, especially if you have a chronic condition that puts you at higher risk. Dr. Gould recommended using an air purifier indoors if possible. (You can make one by gluing a furnace filter to a box fan.)
It is not always possible to avoid going outside on days when there is a lot of smoke. If you absolutely must do so, avoid strenuous exercise and wear an N95 mask.
There are no clear answers about when exactly you should avoid exposure to smoke outdoors, but public health officials often issue health warnings when the AQI index is above 100.
Dr. Cleland recommends checking air quality reports in the summer and fall, much like you check the weather. “People tend to react if they see, smell or feel smoke, but the health effects happen before the smoke reaches that level,” she said.
