Nightly News | April 24, 2013
>>> new stats out tonight about our air and our cars. first off the american lung association and teheir state of the air report says 42% of us live in counties with unhealthy levels of air pollution . the good news, our air is generally cleaner and 16 u.s. cities are at their cleanest ever. most congested u.s. city, by the way, no surprise. los angeles . takes the crown.