The 10 dirtiest cities in America

The booby prize this year for Dirtiest City in America goes to Fresno, California. This Central Valley city suffers some of the worst air in the nation, and a water supply so degraded that the city used to tell pregnant women not to drink from the tap. Fresno epitomizes the environmental challenges of the Golden State. 

A bright spot in the pollution landscape is that according to this EPA report, America's air quality has generally been getting better. Cars and trucks are more efficient, fuel blends are cleaner, and coal-fired power plants have been forced to install air-scrubbing technology.

But lord knows we have a long way to go.
Much of the data for our list of the 20 Dirtiest Cities In America (of which Yahoo! Homes is publishing the top 10 here; go to Forbes.com to see the remaining half) is derived from rankings done by Bert Sperling on his Bestplaces.net website. Sperling is known for for his books like "Best Places To Raise Your Family" and "Cities Ranked And Rated." His website features tools that let you slice and dice cities by a whole host of categories, like cost of living and income, as well as by water and air quality.
See the rest of the top 20 dirtiest cities on Forbes.com:

Sperling's air quality index is based on annual data from the EPA, which factors in ozone and pollutants like carbon monoxide, sulfur dioxide, lead and volatile organic chemicals.
Likewise, his water quality rankings use EPA data that measures watershed quality by looking at 15 indicators like pollutants, sediments, and toxic releases.
Both indices rank metro areas into an index where 1 is the worst and 100 is the best.
To get a set of dirty cities, we identified which metro areas (with population of 500,000 or more) showed up on both lists for poor water quality and air quality. Then we averaged their rankings on the indices. We then took a look at some other sources, such as EPA data on the big cities with the most toxic releases, the American Lung Association's annual State of the Air report, as well as a look at the prevalence of Superfund sites in the various areas.
Informed by these other sources, we bumped cities up and down on the list.
It's a fascinating exercise to comb through reports on Superfund projects -- they're a reminder of how disgracefully careless many manufacturers were in decades past.
I was surprised to find that in Silicon Valley, south of San Francisco, there are 28 one-time Superfund sites in locations where semiconductor manufacturers like Intel, AMD and Fairchild once had fabrication plants. To maintain ultra-clean facilities the chipmakers used oceans of solvents like trichloroethene, which were stored in tanks under the plants. And leaked. According to a 2009 EPA update, groundwater contamination at numerous sites including Fairchild and National Semiconductor remains pervasive and is monitored and vented. The surface though has been reclaimed, and a big office building now sits there. Yet the San Jose, Sunnyvale, Santa Clara metro still ranks 8th dirtiest in the nation. American manufacturers have learned the hard way how to clean up their act. Their legacy unfortunately will continue to effect the health of their communities for many years to come. We can only hope that the economic growth miracles underway in places like China and India and Brazil will be accompanied by more environmental care than was America's own economic heyday.
Here are the 10 dirtiest cities in the nation.
1. Fresno, Calif.
The Fresno-Madera metro area takes the prize for dirtiest city in America. The 500,000 people in this area suffer from being exposed to groundwater polluted by agriculture as well as having the 5th worst year-round particle pollution in the nation, according to the American Lung Association. Sperling Air Quality Index: 1 Sperling Water Quality Index: 22
2. Bakersfield, Calif.
Bakersfield is the oil capital of California, home to some of the oldest and biggest fields in the nation. Emissions from oil and gas processing contributes to Central Valley air pollution that is the worst in the nation. According to the Lung Association, the population of 800,000 is subject to the worst particle pollution in the country and third-worst ozone. Sperling Air Quality Index: 1 Sperling Water Quality Index: 42
3. Philadelphia, Pa.
The Philadelphia - Camden - Wilmington metro area sits on the Delaware River, which has been lined with refineries and chemical plants for decades. The region has 18.5 million lbs a year of toxic releases, according to the EPA, with 7.2 million lbs discharged into the water. Superfund sites include the Franklin Slag Pile and the Martin Aaron site. Sperling Air Quality Index: 22 Sperling Water Quality Index: 12
4. Bridgeport, Conn.
Despite being in one of the nation's richest states, much of Bridgeport remains blighted. For decades the Raymark Industries site manufactured car parts and asbestos and filled in wetlands by dumping toxic waste on them. The EPA has been removing lead, asbestos, arsenic and dioxins for 20 years. Sperling Air Quality Index: 8 Sperling Water Quality Index: 32
5. Modesto, Calif.
Modesto is another polluted city in California's Central Valley. It's 500,000 people have a 15.5% unemployment rate, rank 5th in short-term particle pollution and 11th in ozone. Sperling Air Quality Index: 6 Sperling Water Quality Index 34
6. Riverside, Calif.
The 4.2 million residents of the Riverside-San Bernardino metro area suffer from high levels of ozone. In 2009 the EPA placed on the Superfund list a site the for decades manufactured explosives, rocket motors and fireworks, and which leaked perchlorate and trichloroethylene, destroying drinking water supplies. Sperling Air Quality Index: 1 Sperling Water Quality Index: 49
7. New Haven, Conn.
The 850,000 residents of the New Haven-Milford metro area may enjoy having a top flight school in Yale University, but due to their location at the intersection of I-95 and I-91, their lungs pay the price. Sperling Air Quality Index: 6 Sperling Water Quality Index: 44
8. San Jose, Calif.
You don't equate Silicon Valley with pollution, but the San Jose-Sunnyvale-Santa Clara metro area is home to more than a dozen Superfund sites where chipmakers like Fairchild and Intel leaked toxic solvents into the earth. Ozone pollution is also a problem. Sperling Air Quality Index: 13 Sperling Water Quality Index: 30
9. Stockton, Calif.
Stockton summer heat exacerbates ozone levels that rank 23rd in the nation. Population is 650,000. The city has little means to fund environmental initiatives. It has sought to avert bankruptcy by laying off city employees, including a quarter of its police force. Sperling Air Quality Index: 15 Sperling Water Quality Index: 35
10. Milwaukee, Wi.
Decades of heavy industrial development along the Milwaukee River has contributed to significant amounts of PCBs and heavy metals polluting groundwater and draining towards Lake Michigan. The 1.5 million residents of the Milwaukee-Waukesha metro endure air that's ranked 20th for short-term particle pollution. Sperling Air Quality Index: 26 Sperling Water Quality Index: 26

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