The horizontal axis shows the upper-bound lifetime cancer risk per million individuals exposed. The vertical axis shows each individual carcinogenic pollutant. 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 risks for different census tracts across the US. For example, to read the risks for arsenic on the chart for risk from all sources, the right-hand end of the bar shows a risk of about 4 in 1 million, denoting the 99th percentile census tract. This means that only 616 census tracts (1% of 61,641 total census tracts) have levels of arsenic-associated inhalation risks higher than this level. Other vertical lines across the arsenic 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 risks higher than 2 in 10 million. The left-hand end of the bar shows the 5th percentile of risk, about 4 in 1 billion. Ninety-five percent of all tracts have a higher arsenic-associated inhalation risk.