America's Top 5 Cleanest Cities What Is a Clean City? Ideally, it's a place where the air quality is good, the water is safe to drink, and factories aren't dumping harmful chemical waste into the environment. It's also a place where you look up and down streets that are free of garbage, and stroll through parks without wading through litter. San Francisco Background: Once a prominent shipping and manufacturing center, San Francisco now has booming financial and business sectors. Since 1980, the city's population has increased by more than a third and its per capita income ranks among the nation's highest. Few places have a citizenry that is more environmentally conscious. Problems: Like nearly every traffic-clogged urban California area, San Francisco has struggled with high emissions of greenhouse gases. Its Hunter's Point area is home to two polluting power plants and a highly contaminated Naval Shipyard. In 2002, a national report found that while San Francisco's source water was safe, its tap water contained high levels of a cancer-causing pollutant known as TTHM. Solutions: The city's Environment Department--something many municipalities lack--is seeking to close the power plants at Hunter's Point, and the federal EPA is overseeing a massive cleanup of the shipyard there. Meanwhile, San Francisco is in the forefront of efforts to promote the use of clean-air vehicles, with its public transit leading the way. The city's bus fleet includes over 700 electric-drive vehicles, with plans to convert all the buses to this clean-air technology by 2020. As for concerns about its drinking water, San Francisco responded by modifying its water treatment process, which brought the TTHM levels back down into the safe zone. Finally, the local government is finding ways to push energy savings. Columbus, Ohio Background: Ohio's capital, according to the latest census, was the only major city in the state to grow in population. And Columbus's geographical expansion continues. Its economy is light on industry-less than 12% of its job force works in the manufacturing sector. The big growth has been in financial and insurance businesses, as well as retail. Meanwhile, per capita income here is slightly below our 50-city average. Problems: Columbus's steady development has made it tough to keep the city's watersheds clean. Also, an aging storm water and sewage system has caused overflows and backups in recent years. Litter has been a manageable problem, although Columbus has a recycling rate of just 4%, which Mayor Michael Coleman calls 'pitiful.' And finally, the late 1990s were marked by a sudden increase in ugly graffiti (涂鸦) on both public and private property. Solutions: The mayor recently unveiled a new initiative, 'Get Green Columbus', which established an office of Environmental Stewardship. Also underway is a program to update the sewage and storm water systems. To spruce up unsightly areas, Columbus has committed to removing graffiti within two days of its appearance. Through the city's Neighborhood Pride program, a handful of communities each year get a solid week of concentrated cleanup, including tree trimming (修剪), bulk trash pickup and litter removal. Buffalo, New York Background: Long known as a Rust Belt City where steel was king, Buffalo was hit hard when that industry went into steep decline more than two decades ago. As steel plants shut down, Buffalo was forced to rebuild its economy from the ground up. But by leveraging its assets, including a low cost of living and cheap, clean hydroelectric energy generated by nearby Niagara Falls, Buffalo has begun luring new, non-manufacturing businesses to the area. Problems: A heavily polluted Buffalo River, acres of brown-fields, dwindling population, shrinking tax base and fiscal problems meant drastic cuts in city services