Table 1.

Sources of PM${}_{2.5}$ emissions by US Census region, in tons, with corresponding proportion of total regional PM${}_{2.5}$ emissions in parentheses from the EPA 2014 National Emissions Inventory (U.S. Environmental Protection Agency, 2014).

Type	Northeast	South	Midwest	West	US Total
Stationary	260,853 (82.7%)	1,181,440 (60.9%)	1,262,981 (81.1%)	568,122 (42.4%)	3,273,396 (63.5%)
Mobile	41,432 (13.1%)	129,699 (6.9%)	97,710 (6.3%)	64,945 (4.9%)	333,786 (6.5%)
Other	13,091 (4.2%)	629,734 (32.4%)	196,898 (12.6%)	705,595 (52.7%)	1,545,318 (30.0%)