Short-term exposure to air pollution, whether from motor-vehicle exhaust, wildfires, or dust from construction sites, is associated with an increased risk of stroke. This link, already established for extended exposure – for instance, over several weeks or months – is seemingly now confirmed with exposure of just a few days.
“Previous research established a connection between long-term exposure to air pollution and an increased risk of stroke, but the correlation between short-term exposure and stroke was less clear,” study co-author Ahmad Toubasi of the University of Jordan in Amman explained.
“Instead of looking at weeks or months of exposure, we looked at just five days and found a link between short-term exposure to air pollution and an increased risk of stroke.”
For the purposes of this study, the researchers carried out a meta-analysis of no fewer than 110 studies involving more than 18 million cases of stroke. Nitrogen dioxide, ozone, carbon monoxide, and sulfur dioxide were among the pollutants they analysed.
They also looked at different particle sizes, including those originating from motor exhaust, the ignition of fuels from power stations and other industries or forest fires (PM2.5), and those emanating from dust from roads and construction sites (PM10).
Published in the medical journal “Neurology”, the study suggests that people exposed to higher concentrations of several of these air pollutants had an increased risk of stroke – as well as death from stroke.
The experts specify that nitrogen dioxide is particularly associated with an increased risk of stroke (28%), followed by carbon monoxide (26%), sulfur dioxide (15%) and ozone (5%).
In terms of particle size, PM2.5 is linked with a higher risk of stroke (15%), followed by PM10 (14%). The researchers also observed an increased risk of death from stroke with higher concentrations of sulfur dioxide (60%) and nitrogen dioxide (33%).
“There is a strong and significant association between air pollution and the occurrence of stroke as well as death from stroke within five days of exposure,” Toubasi added. “This highlights the importance of global efforts to create policies that reduce air pollution.
It should be noted, however, that this research does not encompass data from all over the world, with the majority of studies included coming from Asia (59%), followed by Europe and the Americas (25% and 17%, respectively).
This is an important detail, since the researchers point out that “most of the studies were conducted in high-income countries, while limited data was available from low- and middle-income countries”.