According to a 2009 American Lung Association report, 6 of every 10 Americans live in counties where ozone or particle pollution has reached dangerous levels. In fact, more than half of Texas residents live in areas that do not meet federal ozone standards. In 2009, Houston was ranked as the 5th most polluted city in the US for Ozone pollution, with the Dallas/Ft. Worth area is not far behind as 7th most polluted.