Air pollution is often thought of as a long‑term environmental problem, but new research suggests that even short bursts of polluted air may have immediate and serious effects on human health.
Scientists studying the massive Canadian wildfires of 2023 have found evidence that the smoke drifting into the northeastern United States may have been linked to an increase in strokes and more severe cases of stroke.
The research was conducted by scientists from Cooper Medical School of Rowan University in Camden, New Jersey. The study is scheduled to be presented at the American Academy of Neurology’s 78th Annual Meeting, which will take place from April 18 to April 22, 2026, in Chicago and online.
Although the findings are still preliminary, they provide important insight into how wildfire smoke may affect the brain and cardiovascular system.
Wildfires in Canada during the summer of 2023 were unusually large and intense. The fires produced huge clouds of smoke that traveled hundreds of miles across North America. As a result, many cities in the northeastern United States experienced dramatic declines in air quality. Skies turned hazy and the air contained unusually high levels of pollution.
Wildfire smoke contains a mixture of harmful pollutants. These include ozone, a gas that can irritate the lungs, and very small particles called particulate matter. These particles are so tiny that they can travel deep into the lungs and even enter the bloodstream.
Scientists have long known that long‑term exposure to air pollution increases the risk of heart disease and stroke. However, less is known about how short periods of intense pollution, such as those caused by wildfire smoke, may affect the body.
To investigate this issue, researchers examined stroke cases recorded in a medical stroke registry. They looked at all strokes that occurred in Camden, New Jersey, during June and July of 2023, when wildfire smoke affected the region. They then compared these cases with strokes recorded during the same months in 2022, when air quality conditions were normal.
A stroke occurs when blood flow to part of the brain is interrupted. This can happen either because a blood vessel is blocked or because a vessel ruptures and causes bleeding in the brain.
The most common type is ischemic stroke, which happens when a blood clot blocks blood flow. Another type, called hemorrhagic stroke, involves bleeding in the brain and is usually more severe and more likely to be fatal.
In addition to collecting stroke data, the researchers analyzed air pollution levels recorded by the U.S. Environmental Protection Agency. Monitoring stations in Camden provided measurements of ozone levels and fine particulate matter, often called PM2.5. These particles are extremely small, measuring 2.5 micrometers in diameter or less.
During the wildfire smoke event in 2023, pollution levels rose dramatically. Ozone levels reached a peak of 136 parts per billion. Under normal conditions, the typical ozone level in the area is around 36 parts per billion.
Fine particulate matter also increased sharply, reaching 211 micrograms per cubic meter, compared with a typical level of about 48.5 micrograms per cubic meter.
Researchers then matched daily air quality data with the timing of each stroke. Because pollution exposure may affect the body over several days, the team also considered pollution levels during the one or two days before each stroke occurred.
The analysis showed that strokes were more common on days when ozone levels were higher than usual. On these higher‑pollution days, there were about 1.25 strokes per day on average, compared with 0.93 strokes per day on days with lower ozone levels.
After adjusting the results for factors such as age, sex, race, and the cause of stroke, the researchers found that higher ozone levels were associated with a measurable increase in stroke occurrence.
The study also suggested that strokes that happened during higher pollution periods tended to be more serious. Researchers observed a greater proportion of hemorrhagic strokes and more cases involving large artery atherosclerosis, which is the buildup of plaque inside major arteries.
The team also examined the effects of fine particulate matter. When levels of these particles were higher than average, patients who suffered strokes tended to have longer hospital stays and higher scores on medical scales that measure stroke severity.
According to the lead author, Dr. Elizabeth Cerceo, wildfire smoke should not be viewed simply as a temporary inconvenience. Instead, it represents a serious public health risk. She explained that the findings help fill an important gap in understanding how short bursts of air pollution can affect the brain and increase the likelihood of stroke.
However, the researchers emphasize that the study has several limitations. The analysis focused on a relatively short period of time during the wildfire event. Because of this, the results should be seen as an early signal rather than definitive proof of a direct cause‑and‑effect relationship.
Another limitation is that the study used daily average pollution measurements. Air pollution can vary significantly throughout the day, and these fluctuations may influence health outcomes in ways that average values cannot fully capture.
The researchers also did not include other environmental factors, such as humidity or atmospheric pressure, which may also affect stroke risk.
Despite these limitations, the study highlights an important public health concern. Wildfires are becoming more frequent and severe in many parts of the world due to climate change. As these events increase, more communities may experience sudden spikes in air pollution similar to those seen in 2023.
The findings suggest that public health officials may need to consider stronger warnings and protective measures during wildfire smoke events. Simple steps such as staying indoors, using air filters, and wearing protective masks may help reduce exposure to harmful particles.
Overall, the research provides valuable early evidence that short‑term exposure to wildfire smoke may increase both the number and severity of strokes. While more studies are needed to confirm these findings, the results underline the importance of monitoring air quality closely during wildfire events and protecting vulnerable populations.
If you care about stroke, please read studies about how to eat to prevent stroke, and diets high in flavonoids could help reduce stroke risk.
For more health information, please see recent studies about how Mediterranean diet could protect your brain health, and wild blueberries can benefit your heart and brain.
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