LOS ANGELES:- California has the most polluted cities in the United States, a report issued on Wednesday said, as President Donald Trump’s administration seeks to force the state to weaken its vehicle emissions standards. The study published by the American Lung Association - which covers the period from 2014 to 2016, the year before Trump took office - said Los Angeles remained the city with the worst ozone pollution, and ranked fourth in terms of year-round particle contamination. Bakersfield, California, number two for ozone pollution, also maintained its position as the city with the worst short-term particle pollution.