Unprecedented Wildfire Pollution Linked to Higher Stroke Risks

When heavy plumes of sepia-toned smoke from the 2023 Canadian wildfires blanketed the Mid-Atlantic, the most immediate visible threat appeared to be respiratory, but for residents of Camden, New Jersey,¹ the environmental crisis was quietly escalating a different kind of health emergency.

An abstract slated to be presented at the American Academy of Neurology’s 78th Annual Meeting indicated that short-term surges in air pollutants during this event were associated with a significant rise in both the incidence and clinical severity of strokes.^2,3

Addressing a Critical Knowledge Gap

Air pollution has long been recognized as a cerebrovascular risk factor, known to exacerbate systemic inflammation, oxidative stress, and endothelial dysfunction.¹ However, although the health effects of long-term exposure to urban pollutants are well-documented, the acute neurological impact of intense, short-term wildfire smoke remained a "critical gap" in medical literature. The 2023 wildfire season, the deadliest in Canada’s history, caused unprecedented declines in air quality across the northeastern US, providing a unique opportunity to evaluate how sudden spikes in ozone and fine particulate matter (PM_2.5) influence stroke etiology and outcomes.

Investigators conducted a retrospective analysis using the Cooper Observational Acute Stroke and Thrombectomy Registry, examining all ischemic and hemorrhagic strokes that occurred during June and July of 2022 and 2023. To ensure the data reflected the physiological delay in pollution impacts, researchers linked each stroke event to pollutant concentrations from the day of the event as well as the preceding 2 days.

During the 2023 wildfires, air quality monitors in Camden recorded ozone levels peaking at 136 parts per billion (ppb), a massive increase from the median concentration of 36 ppb. Fine particulate matter reached 211 µg/m³ compared with a median of 48.5 µg/m³. On days with above-average ozone levels, the incidence of stroke rose to 1.25 cases per day compared with 0.93 cases per day on days with below-average levels. After adjusting for age, sex, and race, researchers found that higher average ozone days were associated with a 0.32 higher daily incidence of stroke.

Pollutant-Specific Impacts on Severity

The study revealed that different pollutants influenced stroke characteristics in distinct ways. Higher ozone levels were specifically correlated with a greater proportion of bleeding (hemorrhagic) strokes and more cases of large artery atherosclerosis, which involves plaque buildup in major arteries. Conversely, elevated levels of PM_2.5—particles 2.5 micrometers in diameter or less—were associated with increased neurologic severity. People who experienced strokes on high-PM_2.5 days presented with higher scores on the NIH Stroke Scale (NIHSS) and required longer hospital lengths of stay. Interestingly, the researchers observed no significant associations between these pollutants and cardioembolic or small vessel stroke etiologies.

The study analyzed a total of 122 strokes. Although the specific demographics of the stroke cohort were adjusted for age, sex, and race, broader surveillance from the New Jersey Department of Health during the same period noted that wildfire smoke disproportionately impacted specific groups. For instance, researchers from Rutgers University found that emergency department visits for asthma during the wildfire event saw a statistically significant increase among females and individuals between the ages of 18 and 40 years.⁴

The researchers acknowledged several limitations, noting that the analysis focused on a very brief wildfire period and represents an "early signal" rather than a definitive long-term picture.² The study relied on daily average pollutant levels, which may have missed the impact of more nuanced hourly fluctuations in air quality. Furthermore, other environmental variables that could influence health outcomes, such as barometric pressure and humidity, were not incorporated into the analysis.

Clinical and Managed Care Implications

These findings have significant implications for managed care organizations and public health officials tasked with disaster preparedness. As wildfires become more frequent due to climate change-driven droughts, the resulting "toxic plumes" represent a complex chemical load of hydrocarbons and heavy metals that can enter the bloodstream and trigger systemic inflammation.

Elizabeth Cerceo, MD, a study author from Cooper Medical School of Rowan University, emphasized the gravity of these environmental shifts.³ “Wildfire smoke contains pollutants like ozone and particulate matter, so it is more than a nuisance; it can be a public health hazard,” she stated. “Our findings show that short-term exposure to elevated air pollution from these wildfires was associated with a higher incidence and severity of stroke.”

The full poster and results will be presented at the American Academy of Neurology’s 78th Annual Meeting being held April 18 to 22, 2026, in Chicago and online.

References

1. Laurent JGC, Parhizkar H, Calderon L, et al. Physicochemical characterization of the particulate matter in New Jersey/New York City area, resulting from the Canadian Quebec wildfires in June 2023. Environ Sci Technol. 2024;58(33):14753-14763. doi:10.1021/acs.est.4c02016
2. Garfinkel L, Jaffri Z, Qureshi H, et al. Acute increases in ozone and PM2.5 during the 2023 Canadian wildfires associated with higher stroke incidence and severity in Camden, New Jersey. Presented at: 78th American Academy of Neurology Annual Meeting; April 18-22, 2026; Minneapolis, MN.
3. Wildfire smoke exposure and increased risk of severe stroke. Press release. American Academy of Neurology. March 3, 2026. Accessed March 3, 2026. https://www.eurekalert.org/news-releases/1118395
4. Surveillance of asthma, mental health, chronic obstructive pulmonary disease, and acute myocardial infarction presenting in NJ hospitals during the June 2023 air quality impacts from the Canadian wildfire event. New Jersey Department of Health Environmental and Occupational Health Surveillance Program. March 2025. Accessed March 6, 2026. https://www.nj.gov/health/ceohs/documents/ceohs%20content/SurveillaneDuring2023WildFires.pdf