Exposure to air pollution, even in the womb, may be linked to genetic changes associated with an increased risk of cancer, researchers said. That finding, from a study done in New York City by scientists at Columbia University, followed 60 newborns and their nonsmoking mothers in low-income neighborhoods, primarily in Harlem and the Bronx. Exposure to pollutants caused chiefly by vehicles was measured by backpack air monitors worn by the women during the third trimester of pregnancy.