Short-term PM2.5 exposure was associated with an increased risk of hemorrhagic stroke hospitalization in Yancheng, China, with the strongest effects observed within the first two days after exposure and more pronounced associations among susceptible populations and during the cold season.
Each 10 μg/m³ increase in PM2.5 concentration was associated with a 3.24% increase in hemorrhagic stroke hospitalization at the lag01 (two-day average) exposure window.
Significant associations between PM2.5 exposure and hemorrhagic stroke hospitalization were also observed at single-day lag0 and lag1 windows.
The association between PM2.5 and hemorrhagic stroke remained significant after adjustment for ozone (O3) but was no longer statistically significant after adjustment for sulfur dioxide (SO2), nitrogen dioxide (NO2), or carbon monoxide (CO).
Stratified analyses identified several subgroups with relatively stronger effect estimates for the PM2.5–hemorrhagic stroke association.
The study was conducted using an individual-level time-stratified case-crossover design based on hospitalization records from four major hospitals in Yancheng, China, between 2022 and 2024.
This research suggests that breathing air with higher levels of fine particulate matter (PM2.5) — tiny airborne particles from sources like vehicle exhaust, industrial emissions, and burning — is associated with a greater likelihood of being hospitalized for hemorrhagic stroke (bleeding in or around the brain) in the short term. Analyzing over 2,300 hospitalized stroke patients in Yancheng, China, the researchers found that for every 10 microgram per cubic meter increase in PM2.5 levels, the risk of hemorrhagic stroke hospitalization increased by about 2.5% to 3.2% over the following one to two days. The effects appeared strongest in the combined zero-to-one-day window after exposure. The study also found that certain groups appeared more vulnerable to this effect, including women, older adults, people with hypertension or diabetes, smokers, alcohol drinkers, and people exposed during cold weather months. These findings add to a growing body of evidence linking air pollution to serious cardiovascular and cerebrovascular events, and highlight that the risk may be especially elevated for people who already have underlying health conditions or other risk factors. One important caveat is that when the analysis accounted for other air pollutants like sulfur dioxide, nitrogen dioxide, and carbon monoxide, the statistical significance of the PM2.5 association disappeared — suggesting that disentangling the independent effects of individual pollutants remains challenging, as they often occur together. Nevertheless, this research suggests that short-term spikes in air pollution may have near-immediate consequences for brain health, particularly among vulnerable populations, and underscores the potential public health importance of reducing ambient air pollution levels.
Qian K, Xu X, Xu C, Jiao Y, Sun Q, Yu X, et al.. (2026). Association between ambient fine particulate matter and hemorrhagic stroke in Yancheng, China.. Frontiers in public health. https://doi.org/10.3389/fpubh.2026.1882030