More than one-third of Americans breathe extra nitrogen oxides, carbon monoxide or formaldehyde

A new study explains why asthma, coughing, wheezing and difficulty breathing, occasionally resulting in hospitalization are common in US homes.

People have cooked over an open flame for thousands of years, but it may be time for a new approach, even better than Natural Gas appliances.

In addition to generating carbon dioxide from using natural gas as a fuel, natural gas appliances also release unburned methane into the atmosphere.

According to a new study led by Stanford University, the amount of methane escaping from natural gas stoves in American households is equivalent to the amount of carbon dioxide emitted by 500,000 gasoline-powered cars.

Home methane leaks contribute roughly a third as much heat as the carbon dioxide produced by the stove’s natural gas combustion, and they also expose users to lung disease-causing pollutants.

The findings, which were published today in Environmental Science & Technology, came as legislators in a number of U.S. cities and at least one state – New York – consider prohibiting natural gas hookups in new construction.

“Surprisingly, there are very few measurements of how much natural gas escapes into the air from inside homes and buildings through leaks and incomplete combustion from appliances,” says study lead author Eric Lebel. “It’s probably the part of natural gas emissions we understand the least about, and it can have a big impact on both climate and indoor air quality.”

Ignored contributor to rising issue

Although carbon dioxide is more common in the atmosphere, methane has a global warming potential that is roughly 86 times that of carbon dioxide during a 20-year period and at least 25 times that of carbon dioxide a century after its release. Methane also harms air quality by increasing tropospheric ozone levels, which are responsible for an estimated 1 million premature deaths due to respiratory diseases each year throughout the world. Since the Industrial Revolution began, methane’s relative content has increased more than twice as rapidly as carbon dioxide’s due to human-caused emissions.

While natural gas pipeline leaks have been extensively examined, natural gas-burning cooking appliances have garnered very little attention.

More than 40 million households in the United States use gas to cook. Cooking appliances, unlike other gas appliances such as space and water heaters, are directly exposed to their emissions, which can include formaldehyde, carbon monoxide, and nitric oxides, which can cause asthma, coughing, wheezing, and difficulty breathing, and can even result in hospitalization. Despite the fact that hood use and ventilation help lower nitrogen oxides and other co-produced pollutants in kitchen air, surveys show that home cooks only use hoods for kitchen ventilation 25–40% of the time.

Consequences and findings

To gain a better understanding of the potential climate and health impacts of cooking appliances, the study monitored methane and nitrogen oxides released during combustion, ignition, and extinguishment in 53 homes in California, not just during combustion, ignition, and extinguishment, but also while the appliance was turned off, which most previous studies did not do. Their research included 18 different gas cooktop and stove brands, with ages ranging from 3 to 30 years.

Cooktops with a pilot light rather than a built-in electronic sparker had the greatest emissions. The amount of unburned methane emitted during around 10 minutes of cooking with the burner was similar to the amount of methane emitted from the puffs of gas emitted while igniting and extinguishing a burner. Surprisingly, the researchers discovered no indication of a link between a stove’s age or cost and its emissions. Most surprisingly, almost three-quarters of methane emissions occurred while stoves were turned off, implying that gas fittings and connections to the stove, as well as in-home gas lines, are to blame for the majority of emissions, regardless of how frequently the stove is used.

Unburned methane from natural gas stoves is expected to account for up to 1.3 percent of the gas consumed, according to the study. While the US Environmental Protection Agency (EPA) does not track individual residential natural gas appliances, it does track methane emissions for all residential appliances. The researchers calculated that overall methane emissions from stoves alone would be significantly higher than the EPA’s current estimates for all home sources.

Larger stoves, for example, tended to release more nitric oxides. The researchers discovered that persons who don’t use their range hoods or have poor ventilation can exceed the EPA’s 1-hour nitrogen dioxide exposure requirements for outdoor exposure (there are no indoor standards) within a few minutes of using the stove, especially in smaller kitchens.

“I don’t want to breathe any extra nitrogen oxides, carbon monoxide or formaldehyde,” adds study senior author Rob Jackson. “Why not reduce the risk entirely? Switching to electric stoves will cut greenhouse gas emissions and indoor air pollution.”

Image Credit: Getty

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