Federal legislation clearly has improved outdoor air quality for all the regulated air pollutants with the exception of ozone, which is a problem in many major metropolitan areas. Debates have focused on the benefits of cleaner air and the value of reducing emissions from coal and industrial facilities, which has led to arguments between the emitter and receiver states and challenges to federal policy. The importance of these arguments has gone on for decades with Northeastern states arguing that their lakes have been acidified by emissions from states to the west. Meanwhile, less attention has been focused on indoor air quality, which is critical because Americans spend nearly all their time indoors and the young and some elderly people spend all their time indoors. The challenge is to measure and manage the regulated pollutants and deal with mold, sick buildings with no windows, tobacco smoke, formaldehyde, and pesticides. In locations with underground sources of uranium, radon is clearly the prominent threat to public health. The imbalance between where the federal government focuses its attention and where the risk is to be found is a challenge to both public health and governments’ reach and need to protect the public.