A study conducted in Ontario has found an association between air pollution, stroke, and atrial fibrillation (a heart arrhythmia).
The strongest association was for stroke and fine particulate air pollution (PM2.5), and it found a linear association to PM2.5 levels as low as 4 or 6 micrograms/cubic meter, levels below the current U.S. standard of 12 micrograms/cubic meter. The U.S. standard of 12 is below the WHO and Canadian standard of 10 12 micrograms/cubic meter. PM2.5 was also associated with atrial fibrillation, though not as strongly as stroke.
Ozone and nitrogen oxide (both are chemicals that cause oxidant stress on humans) were also associated with both stroke and atrial fibrillation, though not as strongly as PM2.5.
The study included all people in Ontario over age 35 who had lived there 5 or more years, starting in 1996.
The study was published in the journal Environmental Health Perspectives: https://ehp.niehs.nih.gov/doi/pdf/10.1289/EHP4883
