Wildfires have been increasing in frequency and duration in the western U.S. and the wildfire season has been increasing in length such that many regions now claim that there is no wildfire season anymore but that wildfires have become a year-round threat. While there are many causes of the increase in wildfires in the western U.S., it is becoming clear that wildfires not only affect forests and grasslands, but also have impacts on the health of populations downwind.