Wildfire smoke is composed of tiny particles and chemicals. As they travel through the air from the site of the fire to you, they often pick up other pollutants and energies from the sun that make them even less healthy than their original forms.
The most massive contiguous structure known to all of human history may very well be the American highway system. If its 41,000 miles were made into a parking lot it would be a cube more than 20 miles on a side and could hold 50 million vehicles. Understandably it’s a great way to get around.