The horizontal axis shows the number of people who live in census tracts where typical individuals have an inhalation hazard quotient above certain levels. The vertical axis shows 28 individual pollutant having a potential to cause adverse noncancer effects (either respiratory or neurological). To the right of each pollutant name is a symbol that indicates the relative level of overall confidence in the emissions information in the National Emissions Inventory, the ASPEN dispersion modeling, and the HAPEM5 exposure modeling for that pollutant. The horizontal bar for each chemical show numbers of people in census tracts exceeding the specified hazard quotient thresholds. For example, to read the bars for chlorine on the first chart, the bar indicates that about 3 million people live in census tracts where inhalation exposure to chlorine exceeds a hazard index of 1.0. The second chart indicates that about 75,000 people live in census tracts where typical chlorine-associated inhalation exposures exceed a hazard index of 10.0. Note that the 75,000 in the higher-exposure tracts are included in the lower-exposure population count of 3 million.