Are gas stoves dangerous? We tested against induction cooktops to find out. - The Washington Post

In 40 million American homes, the “click” of a gas stove igniting is the sound of dinner.

But millions of people are questioning whether they should keep this classic American appliance in their kitchen. For decades, a steady drumbeat of studies has pointed to the risks of burning methane in our homes, from asthma to chronic respiratory diseases, especially in children and the elderly. Electric Cooker With Induction Hob

Are gas stoves dangerous? We tested against induction cooktops to find out. - The Washington Post

Does that mean you should ditch your gas stove?

Scientists’ best answer, at the moment, is: We’re not sure yet. There’s no doubt pollutants produced by gas stoves, including nitrogen dioxide (NO2), formaldehyde and benzene, harm your health. What we don’t know is whether the amounts spewed by gas stoves into your home can make you sick.

So we launched an experiment to help shed some light on the dilemma. We tested how pollutants from cooking infiltrate a typical American kitchen equipped with a gas stove, and the steps Americans can take to protect their health.

To do this, we teamed up with RoundhouseOne, an environmental monitoring and analytics lab, to measure gas stove pollutants in a kitchen in Oakland, Calif. We deployed 12 commercial sensors for four weeks. To gauge what the average American might be breathing in each evening, we monitored what was in the air each day, particularly NO2 and particulate matter. Then we cooked burgers and pasta on a gas stove, and prepared the same meals on an electric induction burner to compare indoor air pollution levels.

“You want to track this data over time because chronic exposure is how these pollutants affect you,” says RoundhouseOne director Archana Ramachandran, an engineer who designed the experiment. “These things are silent killers.”

Our findings suggest that some people — particularly those with respiratory or heart conditions, the elderly and children — may have reason to worry. Based on several safety standards, levels of pollution detected by the sensors regularly rose to hazardous levels. But the exercise also revealed some fairly easy and effective ways to minimize those risks.

It also changed the way we cook.

Millions of Americans have been cooking on gas ranges with dubious ventilation since the early 20th century even as concerns about gas stoves have been simmering for most of that time.

As far back as 1907, minutes from a meeting of the Natural Gas Association of America suggested “no gas of any kind” should be burned on a stove without venting outdoors. Yet stoves are the only major gas-burning appliance permitted to vent their exhaust into the home. Building codes and state regulations specify water heaters and furnaces, which also burn methane, must vent outdoors to prevent the buildup of dangerous pollutants and gases.

This cocktail of emissions includes formaldehyde, carbon monoxide, NO2, an irritant implicated in asthma and other respiratory problems, and particulate matter, which scientists have linked to heart and lung disease, asthma attacks and emergency room visits.

“We know that being exposed to those pollutants is not beneficial to your health,” says Michael Johnson, technical director at the Berkeley Air Monitoring Group, a consultancy researching household air pollution. “We also have a fair degree of certainty that concentrations [of pollutants from gas stoves] often exceed what’s deemed healthy.”

But proving gas stoves make people sick has been trickier. In 2022, the question over gas stove safety exploded into public view after a 2022 peer-reviewed study, drawing on decades of data from the U.S. Census Bureau and hundreds of other studies, estimated 13 percent of cases of childhood asthma in the United States could be blamed on gas stoves. Critics pointed out lots of other factors, from car exhaust to allergens, could be at fault.

The American Gas Association, a powerful trade group representing the U.S. natural gas industry, admits that gas stoves emit harmful pollutants but asserts there are “no documented risks to respiratory health from natural gas stoves from the regulatory and advisory agencies and organizations responsible for protecting residential consumer health and safety.”

The issue quickly became another front in the U.S. culture wars as those on the left and right picked sides in the debate.

Yet none of this could tell Americans much about how these emissions might affect them in their kitchen. The sensors we installed gave us some insight.

For our first test, we chose pasta. Because boiling water releases only water vapor, not particulates, we could largely isolate the effects of burning methane, compared with electricity, on air quality. Most particulates are released from the food we cook, not the fuel source.

Boiling water doesn’t seem like it would worsen air quality, but the results were unambiguous. Concentrations of NO2 soared after lighting the gas stove, while hardly budging when boiling water with induction. Overall, the maximum NO2 level when we used gas was more than twice as high as when we used the induction plate.

How dangerous were the levels coming out of the stove? There’s no definitive standard to judge safety. Despite millions of Americans being exposed to NO2 from stoves daily, government agencies have not agreed on a safe level of exposure to stove chemicals indoors. The United States still has no federal guidelines for safe indoor exposure.

But among the scientific standards that do exist, which focus on air quality outdoors, the levels in our kitchen were too high for comfort. Sensors in our kitchen registered an average of 0.07 ppm over about 20 minutes while cooking with a gas stove, and peaked at 0.16 ppm.

According to California’s standards for outdoor air, exposure to NO2 shouldn’t be more than 0.18 ppm over one hour. Federal hourly standards are even more stringent: They consider exposures above 0.10 ppm to have the potential to harm human health.

Because indoor air pollution standards are typically more stringent than those for the outdoors, where air movement and humidity is greater, the levels in our kitchen suggest health risks comparable to or perhaps higher than similar outdoor concentrations, says Ramachandran.

The air quality in our test kitchen wasn’t great even before turning on the gas stove. During the four weeks before the test, ambient levels of NO2 concentrations averaged 0.033 ppm. That’s above what the California Air Resources Board believes is harmful to human health among vulnerable populations over the course of a year.

What was the source of NO2? RoundhouseOne could not identify it but said it might have been the stove’s always-on pilot light leaking methane or other combustion sources such as heaters or furnaces.

Next, we cooked burgers. Unlike boiling, frying or sauteing can send plumes of tiny oil droplets or charred food particles into the air. Searing ground beef illustrates a typical household’s exposure when cooking at home, given the average American eats the ground beef equivalent of two burgers per week.

As before, NO2 levels spiked over the 10-minute test when cooking on gas but stayed relatively low during induction cooking. But particulates, especially the smallest hazardous microscopic particles known as PM 2.5, jumped compared with when we were boiling water.

Within minutes of searing patties over the induction plate and the gas stove, levels of particulates spiked to undesirable levels as measured on the Environmental Protection Agency’s Air Quality Index (AQI) scale, a composite index estimating major pollutants including PM2.5, which is implicated in respiratory and heart disease.

During our burger experiment, AQI levels quickly rose past 100, the threshold considered “unhealthy” for sensitive groups such as children and the elderly. Eventually, AQI measurements peaked above 250, considered “very unhealthy” for everyone.

By comparison, last year’s Canadian wildfires sent D.C. near the top of the list of major cities on Earth with the worst air quality when AQI readings hit 155 in July.

To take care of particulates, we would need to clear the air.

Yes. For each experiment we cooked with the vent hood off and on. We found the hood helped — just not nearly as much as expected.

Our hood, a small model which sucked up the air above our stove and vented it outside, seemed to make a difference for NO2. When we cooked with gas and turned it on, levels of the pollutants reached much lower levels.

But the hood didn’t make that a big of a difference for particulates. In our case, pollutant levels crept up, often to hazardous levels, despite running our kitchen hood at full blast. The concentration of particulates was so high, it would have taken much longer than the time we spent cooking for the hood to clear the air on its own, says RoundhouseOne’s Ramachandran.

Good ventilation is probably the only effective measure you have to protect yourself from emissions that come directly from the food, especially if you have a hood that vents outside.

But millions of people do not have them. Even if they do, the effectiveness of the appliance varies. Studies on hoods are complicated. Some show reductions in NO2, while others show little difference. A lot has to do with what equipment is in your kitchen. “Not all ventilation is created equal,” says Heather Miller, a research associate with Berkeley Air Monitoring Group.

A study by Lawrence Berkeley National Laboratory showed hoods could remove anywhere between 15 percent to 98 percent of pollutants based on the model and the burner that was used — the machines captured more pollutants from rear burners. The most effective hoods were open, scoop-like hoods that vent to the outside, like the one we used in our study. Much less effective — and far more common — are overhead flat-bottomed microwave hoods and “ductless” hoods which recirculate fumes through activated charcoal filters.

What worked best to reduce pollutants in our experiment? Opening the windows, and circulating fresh air with a fan and an air purifier. Particulate and NO2 readings fell close to near zero within three to four minutes after doing that.

But that’s asking a lot. Even in households that have hoods, fewer than half turn them on because of their noise and annoyance. And it’s not always practical to open windows and doors when you cook.

Cooking once in a smoky kitchen isn’t particularly dangerous. It’s the cumulative exposure that matters. The daily, weekly and monthly cadence of elevated pollutants increases the risk of disease down the line. This elevated risk may even be nominal for a healthy person.

But for the most vulnerable — the elderly, children, and those with respiratory or heart conditions, or predispositions to them — the risk can’t be easily dismissed. New studies are now underway to pinpoint the precise risk posed by gas stoves.

The message Johnson of the Berkeley Air Monitoring Group wants to send boils down to this: Avoid gas if possible, but you don’t need to rush out and remodel your kitchen.

“If you are a healthy person without kids, it’s probably not going to matter that much,” he said. “But if you have underlying health conditions or young kids or older people at home, you might want to think about ways to transition to a clean source for cooking.”

The good news is that many of the same health benefits from ditching gas can be achieved for very little money with more airflow.

For starters, open a door or crack the window, and turn on any available ventilation. This brings fresh air indoors, vents cooking fumes outdoors and can significantly reduce health risks for sensitive populations — although not everyone has that option, especially in lower-income housing.

For renters or homeowners, these are some quick fixes.

You can go electric without replacing your gas stove. For this experiment, we bought a countertop induction burner ($112 new, $50 used). The induction plate, which sits atop any surface, delivered plenty of power to cook our meals while plugging into a standard electrical outlet. A high-quality toaster oven ($169) can tackle most daily cooking without the need to ever turn on the gas.

Breaking up isn’t easy.

But switching to induction comes with benefits. Boiling water takes less than a minute. You can saute anything with perfect precision. And there will be no more methane leaks or NO2 emissions inside your home. Equally important, it can get American homes closer to cutting their gas line completely.

The fossil fuel industry has treated gas stoves as a gateway appliance that keeps a gas line running to your house, enabling gas-powered space and water heating, the two main consumers of residential gas. Stoves make a minimal direct contribution to U.S. greenhouse gas emissions: just 0.1 percent, according to Daniel Cohan, an associate professor of environmental engineering at Rice University. But even one gas appliance needs to be plugged into the massive — and leaky — infrastructure that pipes methane across the country, which is as bad for the climate as coal by some estimates.

Are gas stoves dangerous? We tested against induction cooktops to find out. - The Washington Post

Index Cooker By making the switch to electric, the only thing you’ll be burning inside are dinners.