The horizontal axis shows the number of people who live in census tracts where typical individuals have an upper-bound lifetime cancer risk above certain levels. 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 three horizontal bars for each chemical show numbers of people in census tracts exceeding three different risk thresholds. For example, to read the bars for arsenic on the chart for risk from all sources, the longest bar indicates that about 18 million people live in census tracts where the upper-bound arsenic-associated inhalation risk to a typical individual exceeds 1 in 1 million. The shorter bar immediately above indicates that about 600,000 people live in census tracts where such risks exceed 10 in 1 million. The shortest bar shows that about 30,000 people live in census tracts where such risks exceed 100 in 1 million. The 30,000 exceeding the highest-risk threshold and the 600,000 exceeding the medium-risk threshold are also included in the counts for people exceeding the lowest risk threshold.