A new study shows that the gas that is piped into millions of California homes contains hazardous air pollutants.

The researchers estimated that each year California gas appliances and infrastructure leak the same amount of benzene as is emitted by nearly 60,000 cars, but these leaks are not recorded.

The debate over limiting the use of gas in homes because of its impact on climate change and public health has been intensified by the publication of the study. Berkeley was the first city to ban gas hookups in new homes and buildings. Dozens of cities in California and across the country have enacted similar laws.

There have been documented health impacts from using gas stove. Eric Lebel, the study's lead author, said that having a gas appliance in your house can have health and climate impacts.

Dr. Lebel is a senior scientist at the Institute for Public Health and Climate Effects of Energy Production.

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Researchers collected unburned natural gas from 159 homes across California served by three gas companies. The air pollutants contained in the samples are known to cause cancer and other serious health impacts.

ImageA hand-held monitor measuring gas coming from a stovetop.
Scientists at PSE Healthy Energy collected and analyzed samples of unburned gas.Credit...Brett Tryon
A hand-held monitor measuring gas coming from a stovetop.

benzene, a highly flammable chemical that can be odorless and colorless, was the most prevalent pollutant. Blood disorders and cancer can be caused by long-term exposure to the chemical.

Dr. Philip J. Landrigan is a public health professor at Boston College. He said there is no safe threshold for exposure to benzene.

The previous studies were from the same group. Researchers found benzene and other hazardous air pollutants in samples of unburned gas collected from residences in the Boston metropolitan area.

Researchers combined the results of the leak and the measurement of benzene in unburned gas to model potential indoor benzene concentrations. The concentration coming from the gas hookup was similar to that found in homes with smokers.

The size of the kitchen is one of the factors that may affect indoor benzene levels. "Simply opening the windows or turning on a range hood while the stove is on" will not eliminate the risk according to a senior scientist at PSE Healthy Energy.

Environmentalists and local officials in states like California and Massachusetts have pushed to phase out gas appliances in favor of electric ones due to the emissions impact of burning fossil fuels. 13 percent of the country's greenhouse gas emissions come from the homes and buildings.

Natural gas is the main component of methane. It can warm the planet more than 80 times as much as carbon dioxide over the course of 20 years.

Drew Michanowicz said that the new research shows that climate and health go hand in hand. He said that energy policies that give tax credits and rebates for electric appliances are a step in the right direction.

Most of the major sources of benzene in our lives are associated with fossil fuels, according to an earth scientist who didn't work on the study. Motor vehicle exhaust, gasoline, and products made with chemicals are some of the sources.

He said that the growing body of evidence of harmful levels of indoor air pollution is a good reason to encourage electric vehicles.