We learned that smoking was bad for our health, but perhaps missed in all that smoke was the danger from the campfire burning away. Because the PM2.5 stuff is clearly more damaging than we ever knew. The American Heart Association writes:
Exposure to PM <2.5 μm in diameter (PM2.5) over a few hours to weeks can trigger cardiovascular disease-related mortality and nonfatal events; longer-term exposure (eg, a few years) increases the risk for cardiovascular mortality to an even greater extent than exposures over a few days and reduces life expectancy within more highly exposed segments of the population by several months to a few years.
Another study notes that "long-term exposure to combustion-related fine particulate air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality."