Andy Larsen: Just how dangerous are gas stoves? To indoor pollution? To your health?

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There’s no more classic news story than That Thing In Your House That You Like Is Actually Dangerous.

Christmas trees? You bet. Those can catch fire. Bookshelves? They fall on children with relative frequency. Snowblowers? They lead to thousands of injuries a year.

The next example in that trend is a focus on gas stoves. In the past year, The Wall Street Journal, The Atlantic, The Weather Channel and other outlets have written about studies that show the way gas stoves contribute to indoor air pollution.

I know that amateur and professional chefs alike love cooking with gas when compared to its coil electric counterpart. The temperature applied is quickly adaptable with gas in a way that’s difficult with electric cooking. And a huge percentage of Americans and Utahns cook with gas stoves. Finding out if they’re harmful, and to what degree, is an important question.

The most comprehensive case against gas stoves was a report published in 2020 by a joint coalition of four groups: the Rocky Mountain Institute, the Sierra Club, Physicians for Social Responsibility, and Mothers Out Front. You can ascribe a motive to at least some of these groups. For example, the Sierra Club may want to see less natural gas extraction in the environment and may thus try to reduce the use of a popular natural gas item. Overall, though, I found the report to be well-researched and pretty darn buttoned up — backing up all the points with impressive research.

The report can be summarized into eight points. In particular, the crux of the case is found in Nos. 2, 3 and 4.

1. Indoor air is largely unregulated and is often more polluted than outdoor air.

2. Gas stoves can be a large source of toxic pollutants indoors.

3. Indoor pollution from gas stoves can reach levels that would be illegal outdoors.

4. There are well-documented risks to respiratory health from gas stove pollution.

5. Children are particularly at risk of respiratory illnesses associated with gas stove pollution.

6. Lower-income households may be at higher risk of gas stove pollution exposure.

7. Ventilation is critical but is not the sole strategy to prevent exposure.

8. Electric cooking is a cleaner household cooking option.

Are gas stoves a large source of toxic pollutants indoors? In practice, it appears so. While gas furnaces and water heaters must have their emissions ducted outdoors by code, no such rule exists for gas stoves in the kitchen.

That seems to have consequences. The most recent research on those consequences took place between January 2020 and May 2021, when scientists studied emissions from gas stoves in 53 homes in seven California counties. These homes were a selection of privately owned homes, Airbnb rentals, and properties for sale on the market. They hung up clear plastic sheets around the ceiling, floors and walls of the kitchen to create an airtight barriers.

Researchers then turned on one stove burner, left it on for at least three minutes, then switched it off. They also tested the ovens. They set the temperature for somewhere between 350 degrees and 425 degrees, let the oven preheat, let the oven cook for 20 to 30 minutes, and then turned it off and let it cool. All the while, they measured how levels of methane, ethane, carbon monoxide and nitrogen oxides were changing in the room. They also measured if the ovens and stoves, when off, were leaking the pollutants.

If I had to set up an experiment to see how much indoor air pollution gas stoves were creating, that’s basically how I’d do it.

They found that the stoves were leaking significant amounts of methane. They leaked most when the stoves were being lit, leaked some when burning the natural gas, and, of particular concern, 49 of the 53 stoves even leaked some methane while the stoves were off completely.

They also found that nitrogen oxides were being released in significant amounts — some in the stovetop burners, but especially in the ovens. Both ovens and cooktops released those nitrogen oxides in amounts that exceeded the Environmental Protection Agency’s outdoor long-term safety standard of 100 parts per billion in a few minutes.

So what does that mean? Well, the methane part turns out to be worrying for climate change. Researchers extrapolated that if the gas stoves in these 53 homes are representative of the all of the gas stoves in the United States, then those stoves have an annual climate impact roughly similar to that of the annual impact of 500,000 average U.S. cars.

You can get slippery with the math here, for sure, but there are more immediate effects from the nitrogen oxides on people’s health.

The EPA’s page on nitrogen oxides notes that “results suggest that short-term exposure to NO2 may be associated with cardiovascular effects and premature mortality and that long-term exposure may be associated with cardiovascular effects, diabetes, poorer birth outcomes, premature mortality, and cancer.”

(Because I’m deranged, I had to stifle a giggle at how “premature mortality” is just sneaked in there among all of the other bad stuff. Plain old “dying sooner” can’t get top billing among all of these other maladies.)

If there’s one thing we know, it’s that small increases in nitrogen oxides clearly lead to asthma in children and adults. One study found that a 15 ppb increase in NO2 corresponded with a 50% jump in annual risk for respiratory symptoms among children and adolescents. Another study found that children in homes with gas stoves have a 42% increased risk of experiencing asthma symptoms.

The American Gas Association, the group that represents the nation’s gas companies (including Utah’s Dominion Energy), has fought back against these articles. These parties may be acting in self-interest, but that doesn’t mean that the counterclaims are inaccurate — they have to be evaluated on the merits.

Their arguments come up a little short, I think. For example, they note that the EPA’s Federal Interagency Committee on Indoor Air Quality (CIAQ) “has not identified natural gas cooking emissions as an important issue concerning asthma or respiratory illness,” which is an appeal to authority but not a great one. As we’ve learned repeatedly during the pandemic, governmental agencies can be slow to react to research.

One study that the AGA cites, “Cooking Fuels and Prevalence of Asthma: A Global Analysis of Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC),” studied a huge number of children (512,707, in fact) and found no association between gas usage and asthma. Which seems impressive, until you see that 70% to 80% of children in the study lived in homes that used gas to cook, and a huge percentage of the others used even more dangerous wood-based open-fire situations to cook where actual smoke leads to asthma — in short, the study didn’t do a good job of creating a dissonant control group.

Finally, they write, for example, that “claims that children in homes with gas stoves have an increased risk of asthma symptoms frequently reference a ‘meta-analyses’ of literature that emphasizes the simple presence of a gas appliance, not appliance usage or other exposure-related factors.” Insisting that the studies examine gas stove usage over gas stove ownership seems a bit pedantic, given the research that has occurred.

Yes, it’s true that there’s no nail-in-the-coffin study that shows that gas stove usage is causing people to get asthma (or other health problems). But if we know that the gas stoves are polluting, and that pollution causes asthma, and that kids who have gas stoves are more likely to get asthma, well, I feel pretty good about connecting A to B.

Personally, I’m an owner of a gas stove and studying this made me a bit queasy.

Long term, I’ll be looking to replace my gas stove with an induction-based option that many chefs say is just as good for cooking as gas, if not better — though cooking with a flame visible does have a decided cool factor that I’ll miss. I’ll also be looking at improving ventilation above my stove — right now, my range hood recirculates these pollutants back into my kitchen, rather than outside.

In the short term, I’m going to open my kitchen window when I cook. Nitrogen oxides? No, thank you.

Andy Larsen is a data columnist for The Salt Lake Tribune. You can reach him at alarsen@sltrib.com.