According to a new study even low levels of air pollution may increase stroke-risk. More from the Annals of Neurology:
The results showed borderline significant associations between same day and previous day fine particulate matter exposures and ischemic stroke/TIA risk. Similar associations were seen with ozone. Despite the fossil fuel industry in the area, fine particulate matter exposures were relatively low relative to other regions in the US, probably because of the proximity to the coast and prevailing wind patterns. “Although the magnitude of elevated risk of stroke/TIA due to PM2.5 exposure was relatively small, the vast majority of the public is exposed to ambient air pollution at the levels observed in this community or greater every day, suggesting a potentially large public health impact.”The sad part is I’m not really sure what you can do to avoid this—not breathe!
These findings support the hypotheses that recent exposure to fine particulate matter may increase the risk of ischemic cerebrovascular events specifically. There is experimental evidence that particulate air pollution is associated with acute artery vasoconstriction and with increases in plasma viscosity (thickening of the blood) which may enhance the potential for blood clots, although this requires further study.