New Research, Same Flawed Methodology On Gas Stoves and Asthma

Researchers from Stanford University recently teamed up with Physicians, Scientists, and Engineers for Healthy Energy (PSEHE) on a new gas stove study (Kashtan et al.) that attempts to link the appliance to increased asthma risk. But like the team’s previous research, the findings relied on unrealistic cooking conditions to conclude:

“Gas and propane stoves increase long-term NO2 exposure to 4.0 parts per billion on average across the United States, 75 percent of the World Health Organization’s exposure guideline. This increased exposure likely causes ~50,000 cases of current pediatric asthma from long-term NO2 exposure alone. Short-term NO2 exposure from typical gas use frequently exceeds both World Health Organization and U.S. Environmental Protection Agency benchmarks.”

Notably, the study comes on the heels of a recent study (Pulozzo et al.) from researchers at the University of Liverpool, Peking University, and the World Health Organization (WHO) – that was funded by the WHO and that Kashtan et al. cites multiple times – that found the opposite:

For asthma, no significant increase in risk for children and adults was found for use of gas compared with electricity… We confirmed that that risk of asthma from gas use was potentially exaggerated in studies with no or limited adjustment for confounders versus those with adjustment for at least one key confounder. In addition, our analysis found no significant increase in risk of wheeze (similar in manifestation to asthma) for gas compared with electricity.” (emphasis added)

As American Gas Association President and CEO Karen Harbert explains:

“Despite the impressive names on this study, the data presented here clearly does not support any linkages between gas stoves and childhood asthma or adult mortality. The two major cited studies used to underpin the Stanford analysis directly contradict the conclusions they have presented. In short, the interpretation of results by Kashtan et al. are misleading and unsupported.”

AGA further details:

  • “Kashtan et al. based their asthma analysis on a large 2024 meta-analysis by Puzzolo et al. published in The Lancet in February of this year, that focused on cooking or heating with natural gas and several health conditions. Puzzolo et al. found no association between cooking and heating with natural gas (vs. electricity) and childhood asthma.”
  • “Kashtan et al. based their mortality analysis on estimates of nitrogen dioxide (NO2) exposure from natural gas stove use and a 2018 meta-analysis by Atkinson et al. on long-term outdoor NO2 concentrations and mortality. Atkinson et al. cautioned against concluding that outdoor NO2 concentrations can increase the risk of dying because there were very small risk estimates, the study results were heterogeneous, and body mass index (a measure of body fat) and smoking – two key health confounders – were not always appropriately accounted for in underlying studies.”
  • “In addition, it is notable that the only meta-analysis that looked at indoor NO2 and asthma did not find an association. Lin et al. And Puzzolo et al. found a lack of association with gas use and morbidity. Collectively, these studies do not support an association of gas use with mortality.”

Let’s take a closer look at Kashtan et al.:

Fact #1: Researchers’ findings are limited and reliant on unrealistic cooking conditions.

To reach their conclusion the researchers used an indoor air quality model validated by a set of 18 residences, referred to as “validation homes,” measured the emission rates from 50 gas, 11 propane and 14 electric stoves. Similar to previous research from the Stanford team, measurements were taken in sealed kitchens across several states and data was input into a model to calculate an estimated exposure rate.

This methodology – that utilizes an empty oven and/or burner or stove top in a kitchen sealed off with plastic tarps – was openly criticized by Vice-Chair of the House Energy and Commerce Committee, Rep. Kelly Armstrong (R-ND).

This model was then bootstrapped with Energy Information Administration Residential Energy Consumption Survey (RECS) data to calculate the distribution of days with 1-hour averaged NO2 exposure exceeding the EPA’s short-term exposure limit. Authors then took this calculation and created a population attribution factor of asthma attributable to the use of gas and propane stoves to claim that natural gas is responsible for approximately 19,000 adult deaths and 50,000 cases of pediatric asthma, and further claim that based on the meta-data in Pulozzo et al., this number is “likely closer to 200,000.”

For a bit of perspective, according to the authors the 200,000 alleged cases “is approximately 10% of pediatric asthma attributable to pollution from road traffic.” This is remarkably similar to PSEHE’s 2022 admission that its findings on benzene emission from gas stoves “are likely lower compared to other source types” and found in such small concentrations of natural gas, that there is no cause for immediate concern.

Fact #2: The study finds that proper ventilation reduces pollutants.

In the testing where there was no plastic partition between the kitchen and the rest of the home, researchers found that little more than half of the tested kitchens exceeded the EPA’s 1-hour ambient benchmark. They essentially reach the conclusion that ventilation is a key mitigating factor when they explain:

Without an outside-venting range hood on and with either one burner or one burner and one oven on, concentrations in over half of the kitchens, living rooms, and bedrooms tested exceeded the Environmental Protection Agency’s (EPA)’s 1-hour ambient exposure benchmark of 100 parts per billion volume.” (emphasis added)

They further clarify their recognition of ventilation as a solution, stating:

“Across a subset of five randomly selected homes, we found that outside-venting hood reduced hour-averaged kitchen NO2 concentrations between 10 and 70 percent.”

And later admit:

“People who lack an outside-venting hood or who do not use their hoods are exposed to 25 percent more long-term stove attribution NO2 than average. Meanwhile, people with a 75 percent capture efficiency outside-venting hood who use it every time they cook are exposed to 70 percent less long-term stove attributable NO2 than average.” (emphasis added)

Ventilation is a solution for any cooking environment no matter the cooking fuel because the cooking process releases fine particulate matter, volatile organic compounds, and numerous other pollutants besides just the NO2 that researchers were focused on. A 2012 DOE sponsored study showed that emission rates from cooking are considerably higher than what is generated from natural gas stoves themselves. For example, using a common cooking ingredient like olive oil generates over 11 times more emissions per hour than what is produced from the gas range.

Fact #3: Some of the researchers and the study’s funder have known biases against natural gas.

Study authors’ affiliations include PSEHE, Stanford University, and Harvard’s Chan School of Public Health, all of whom have authored earlier indoor air quality research that has been criticized for numerous flaws, questionable methodology, backtracking, and poor findings.

PSEHE is the coordinator of most of these IAQ studies, and is a frequent partner to broadside attacks on natural gas’s role in the energy sector. PSEHE’s founder and current senior fellow, Anthony Ingraffea, has openly and frequently articulated the organization’s anti-fossil fuel stances, bragging that his research is “a form of advocacy.”

The organization has received significant funding from various foundations with anti-fossil fuel agendas – including The Rockefellers, The Park Foundation, The Heinz Endowments, and The Energy Foundation. These foundations have also funded anti-fossil fuel groups such as Food & Water Watch, Sierra Club, RMI, and Earthworks, among many others.

Additionally, PSEHE has received funding from the High Tide Foundation, which also issued the grant for Kashtan et al. and previous gas stove research.

Bottom line: PSEHE’s new study follows the same flawed strategy of using a small sample of homes, modeled studies, and plastic tarps to scare consumers into thinking their gas stoves are causing health impacts.

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