From USA Today:
"California again leads list with 6 of the top 10 most polluted U.S. cities"
California's smoggy reputation appears to be deserved: Six of the USA's 10 cities with the worst air pollution are in the Golden State, according to a new report. Bakersfield, Calif., again holds the dubious distinction of having the USA's most days of highly polluted air, based on data from 2013-2015, the American Lung Association’s annual “State of the Air” report released Wednesday found.
In addition to the worst spikes of short-term pollution — led by Bakersfield — the report also lists the cities with the worst overall year-round pollution — led by Visala/Hanford, Calif.— and the worst ozone pollution, led by the Los Angeles/Long Beach area. California's soaring population and topography allow air pollution to overcome the state's strict environmental laws, said Paul Billings of the American Lung Association. The boom in people brings with it an increase in cars and trucks on the roads, and many of those people live in valley and basins, right where pollution tends to settle.
Nearly year-round sunny skies also don't help: Those picture-perfect days are a major factor in high levels of ozone pollution, he added. The state would be far worse off without its strict laws on tailpipe pollution and eliminating coal-fired power plants. "They've done more than any other state to counteract air pollution," Billings said. Overall, the report is a mixture of good and bad news: While year-round pollution has improved, short-term spikes of intensely polluted air have increased. "While most of the nation has much cleaner air quality than even a decade ago, many cities reported their highest number of unhealthy days since the report began" 18 years ago, it found.