Wildfire smoke is small enough to enter your bloodstream
Invisible particles from a single forest fire can travel across an entire continent in days, crossing the blood-brain barrier once they reach your lungs.
When a massive wildfire erupts in the western United States, it lofts plumes of soot so high that they hitch a ride on high-altitude winds, crossing the entire continent in less than a week. While the haze might look like a simple cloud, it is actually composed of trillions of microscopic solids known as PM2.5. These particles are less than 2.5 micrometers wide, or about 1/30 the width of a human hair. Because they are so small, they bypass the body's natural filters in the nose and throat, traveling deep into the lungs where they slip directly into the bloodstream to circulate through every major organ.