The horizontal axis shows the hazard quotient. The vertical axis shows each individual pollutant having a potential to cause adverse non-cancer effects. 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 Toxics Inventory, the ASPEN dispersion modeling, and the HAPEM4 exposure modeling for that pollutant. The horizontal bar for each chemical indicates the range of typical hazard quotients for different census tracts across the US. For example, to read the hazard quotients for acetaldehyde on the chart for hazard quotient from all sources, the right-hand end of the bar shows a hazard quotient of about 0.4, for the 99th percentile census tract. This means that only 616 census tracts (1% of 61,641 total census tracts) have a higher hazard quotient associated with inhalation of acetaldehyde. Other vertical lines across the acetaldehyde bar show different percentiles, as indicated by the key in the lower right of the chart. For example, the 50th percentile line shows that half the census tracts have hazard quotients higher than 0.05. The left-hand end of the bar shows the 5th percentile hazard quotient, about 0.004. Ninety-five percent of all tracts have a higher hazard quotient for acetaldehyde inhalation.