[ad_1] For decades, scientists have worked to clean up air pollution from factories, cars and power plants. But researchers are increasingly turning their attention to the air that people breathe indoors. And one appliance has come to the fore as a source of pollutants harmful to human health: the humble gas stove. A new study from researchers at Stanford University sheds light on how much Americans may be exposed, indoors, to nitrogen dioxide, which comes from burning coal and gas and has been linked to asthma and other respiratory conditions. The researchers found that, across the country, short-term nitrogen dioxide exposure from typical gas stove use frequently exceeded benchmarks set by both the World Health Organization and the United States Environmental Protection Agency. In the longer term, using gas or propane stoves meant that the typical American could breathe in three-quarters of the nitrogen dioxide levels deemed safe by the W.H.O. within their own homes. As with outdoor pollution, disadvantaged households may be more exposed, the researchers found. Because gas more easily spreads throughout smaller …