No. 5: Hanford–Corcoran, Calif.
Population: 150,000
Short-term particle pollution rank: 10
Year-round particle pollution rank: 8
Ozone pollution rank: 6
Hundreds of aircraft based at the giant Naval Air Station in nearby Lemoore doesn’t helpHanford’s air quality.

See the others after the jump…

No. 4: Visalia–Porterville, Calif.
Population: 430,000
Short-term particle pollution rank: 8
Year-round particle pollution rank: 3
Ozone pollution rank: 3
Proximity to the giant trees of Sequoia National Park isn’t enough to clean Visalia’s smoggy San Joaquin Valley air.

No. 3: Fresno–Madera, Calif.
Population: 1.1 million
Short-term particle pollution rank: 2
Year-round particle pollution rank: 6
Ozone pollution rank: 4
Cars, agriculture, petroleum and mega-dairies all contribute to the brown haze that hangs over the San Joaquin Valley.

No. 2: Los Angeles–Long Beach–Riverside, Calif.
Population: 17.8 million
Short-term particle pollution rank: 4
Year-round particle pollution rank: 3
Ozone pollution rank: 1
University of Calgary researchers found in 2008 that salty coastal air mixed with sunshine and pollutants helps create unexpectedly high levels of ground-level ozone.

No. 1: Bakersfield, Calif.
Population: 800,000
Short-term particle pollution rank: 1
Year-round particle pollution rank: 2
Ozone pollution rank: 2
Hot, dusty and surrounded by California’s San Joaquin Valley oil fields, Bakersfield has all the ingredients for the worst air in the nation

At the ballot box this November California voters showed that they are determined to clean up their state’s deplorable air quality. They quashed Proposition 23, which would have temporarily suspended key emissions-reduction tenets in the Golden State’s Global Warming Solutions Act of 2006. How temporarily? Until pigs fly, or rather until the state unemployment level dropped to 5.5%–from the 12.4% it’s at now.

Having survived the challenge (62% of voters rejected Prop 23) the emissions cuts are now set to begin in 2012. A carbon cap-and-trade program will be launched later. The goal is that, in eight years, California will have greenhouse gas emissions 15% lower than they are now.

That’s good news for the lungs of Californians. The American Lung Association, in its report State Of The Air 2010, finds seven California metropolitan areas with air quality bad enough that they make it onto the list of the Top 10 Dirtiest Cities in America. The 20 million people in these cities are at higher risk of asthma and chronic bronchitis.

Most of those souls (17.8 million) inhabit the Los Angeles, Long Beach and Riverside area, which ranked second-worst overall and worst in ozone pollution. Aside from millions of cars on the roads, the area also suffers the effects of the nation’s busiest port. Researchers at the University of Calgary found in 2008 that salty coastal air mixed with sunshine and pollutants helps create unexpectedly high levels of ground-level ozone.

The biggest problem spot in the country is California’s San Joaquin Valley, where farming, industry, car culture and topography collide to trap smog. Wildfires contribute to the problem. Severe particle pollution in valley burgs like Bakersfield (the center of California’s oil industry and the metropolitan area with the worst air in the nation), Fresno (third place), Visalia (fourth) andModesto (eighth) can damage the lungs in the same way cigarettes do. Sacramento (ninth) incentivizes residents to trade in gasoline lawn mowers for electric ones, diesel-powered trucks for hybrid ones and old wood stoves for new ones. The only non-California cities in the top 10:Pittsburgh, Pa; Birmingham, Ala.; and metropolitan Phoenix, Ariz.

It’s hard to argue against cleaner air. Thus the debate leading up to the vote on Prop 23 was effectively framed as good vs. evil. On the good side were environmentalists and the sensitive pink lungs of asthma-prone children. On the evil side: power plants, oil refiners and diesel truck drivers.

The biggest backers of Prop 23 were Texas-based oil companies like Tesoro and Valero Energy and Koch Industries (owned by the Tea Party-backing billionaire Koch brothers), all of which have operations in California. Valero, for its part, put up $5 million for a media campaign attempting to convince California that the Global Warming Solutions Act is a job-killer. So too did truck drivers who spew particulates from their diesel engines while hauling loads to and from the Port of Long Beach.

If only those workers knew that their jobs were killing them. The American Lung Association says that truck drivers, dock workers and railroad workers who inhale diesel exhaust are much more likely to die from lung cancer and heart disease than the general population.

Under the law, refiners will have to foot the bill for pollution control technology at their plants, and will also have to provide even cleaner automotive fuels than California already mandates. Valero, which owns two refineries in the state and employs 1,600 workers there, will be able to pass on some of these costs to motorists, but higher fuel prices will almost certainly mean less demand for fuel. Cars are thought to be responsible for as much as 30% of California’s greenhouse gas emissions.

They didn’t get any sympathy from Gov. Arnold Schwarzenegger, who opposed Prop. 23–and who signed the original 2006 global warming legislation. Last week Schwarzenegger, wearing a pair of tough-looking cowboy boots, celebrated the vote and lambasted the oil companies: “We made it clear if those interests push us around,” he said, “we’ll push back.”

The trouble will come if that push-back pushes industry out of the state altogether. Prop 23 supporters insist that a bevy of new taxes on energy will raise the costs of doing business enough to drive companies and jobs out of California. The green crowd insists the Global Warming Solutions Act will spur a clean energy boom in the state–with Californians putting their entrepreneurial talents toward inventing new solar panels, wind turbines and the like.

Some of the biggest opponents of Prop. 23 were Thomas Steyer, whose Fallon Capital Management hedge fund says it invests in areas that will become profitable “due to a catalyzing event or change in circumstances, including regulatory or legislative change.” Steyer was joined by billionaires including John Doerr, rainmaker at green-tech venture capital shop Kleiner Perkins.

One company set to benefit from the law is SPG Solar, California’s second-biggest solar panel installer. SPG will likely be hiring more installers in the years to come–but will the real boom in green jobs be in California? SPG President Tom Rooney tells Forbes he’s thinking of opening a panel factory in China.

Even if green energy companies don’t take their manufacturing overseas, there’s little reason to build factories in high-tax California. Better to invest in low-tax Texas, which already boasts the world’s highest concentration of energy companies, in Houston (a perennial polluter chock-a-block with refineries), which narrowly escaped the top 10 Dirtiest Cities cut.

With any potential for a nationwide carbon cap-and-trade scheme now crushed by Republicans taking over the House of Representatives, America will be watching California for cues on whether greenhouse gases can be ameliorated without killing economic growth.

Our lungs hope for the best. According to the Lung Association 175 million Americans live in counties where outdoor air quality earned a grade of F. And if the Global Warming Solutions Act does end up being a job-killer, at least there’s a bright side–unemployed Californians will have cleaner air to breathe.