A new report finds 46 percent of U.S. children live in places that get a failing grade for at least one measure of pollution. That's according to the American Lung Association's annual state of the air report. The report looks at two of the most widespread and dangerous air pollutants: fine particles and ozone. It found Kern County in California was the most polluted county year-round followed by Cameron in Texas and Lane in Oregon. Seven of the ten worst counties were in California.