Brett Singer and colleagues at the U.S. Department of Energy's Lawrence Berkeley National Laboratory tested gas ranges to determine their pollution output.
The researchers used data on more than 6,000 Southern California households and their cooking habits to estimate people's exposure to air pollutants in the kitchen during a typical week in the winter.
They discovered 62 percent of households using gas burners without venting range hoods were routinely exposed to excessive levels of nitrogen dioxide, 9 percent to carbon monoxide and 52 percent to formaldehyde -- gases that can cause respiratory problems and worsen asthma and cardiovascular disease, the Los Angeles Times reported
"Even in Los Angeles, those pollutants don't exceed air quality standards outdoors," Brett Singer, a staff scientist who studies indoor air quality at Berkeley Lab, told the Times. "But inside homes they do."
The study, published in the journal Environmental Health Perspectives, estimated as many as 12 million Californians are exposed to levels of nitrogen dioxide above health standards as a result of cooking with gas burners. Nationally, there could be tens of millions more.