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In April, San Francisco's mayor, Gavin Newsom, signed an ordinance to reduce the single largest source of diesel pollution in the city, which, you may be surprised to learn, consists of bulldozers, cranes, and other heavy construction equipment. City contractors performing major projects (longer than 20 days) will soon be required to use cleaner equipment and fuel that contains a minimum of 20 percent biodiesel, which emits less asthma-triggering particulate matter, toxic pollution, and carbon dioxide than does standard diesel. Contractors must also notify schools and hospitals near construction sites before projects begin so that children and patients with respiratory ailments can make plans to minimize their exposure to construction pollution. "San Francisco is putting public health first, and we hope other cities will follow," says Diane Bailey, an NRDC scientist who provided scientific and technical support for the new ordinance. Later this year, the California Air Resources Board is expected to vote on a similar, statewide rule.