Population-weighted mean NO₂ concentration in ppb (percent of total population<i>1</i>).

<p>^<i>1</i>Population totals may be less than 100% because of rounding, nonresponses in Census data, and category definitions (e.g., population >25 years old is 66% of total population).</p><p>^<i>2</i>Each race-ethnicity category in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094431#pone-0094431-t001" target="_blank"><b>Table 1</b></a> includes people who reported a single race category and non-Hispanic ethnicity (i.e., “White” category is “White alone; non-Hispanic”), except for the “Hispanic” category, which includes people who reported any race(s) and Hispanic ethnicity, and the “Black Hispanic” category, which includes people who reported Black race alone and Hispanic ethnicity.