Cooking up pollution: A study on how gas stoves affect indoor air pollution.

By: Dan Jaffe, Devon Nirschl, Stephanie Birman

Does your stove result in bad air pollution?

It’s been a big few years for gas stoves and the natural gas industry. Following the publication of research linking gas stove use to childhood asthma, the US Consumer Product Safety Commission moved to regulate gas stoves federally in January 2023. A couple months later, New York became the first state to ban natural gas appliances in new residential buildings (Nilsen, 2023). Closer to home, Governor Jay Inslee signed new legislation to reduce the use of natural gas (Robertson, 2024) in March 2024. We last wrote about gas stoves in February 2023 (see post here), laying out the risks associated with cooking with a gas stove, as well as how you can view and improve the air quality in your home. We also put out an invitation to our readers to help our team at UW collect indoor air quality (IAQ) data in homes with IAQ risk factors. Since then, we’ve analyzed the data from 14 homes around the United States and plan to continue studying this more in depth.

Background

              For this study, we focused on four pollutants. Three, , CO, CO2, and NO2, are emitted during fuel combustion in gas stoves. The fourth, fine particulate matter smaller than 2.5 um in diameter (PM2.5), comes from cooking food. There’s no set standard for indoor air quality so we used the EPA’s Air Quality Index (https://www.airnow.gov/aqi/aqi-basics/) and defined “unhealthy air” as any values with an Air Quality Index greater than 100 (see https://www.airnow.gov/aqi/aqi-basics/ for details).  For CO2 we used a level of 2000 ppm, a level that has been shown to cause health impairments (Jacobson et al., 2019) 

The Study

Volunteers were sent a TSI AirAssure device for two weeks that measured the four indoor pollutants focused on in the study: CO, CO2, NO2, and PM2.5. Volunteers were asked to record data including stove use (in minutes), oven use (in minutes), and mitigation efforts. For their first week, participants were to cook and use their oven/stove as usual. In the second week, participants were to add in mitigation efforts. These could include using an exhaust fan, opening a window, and/or using a HEPA air purifier. After data was collected, our team used the AQI to quantify pollutant exposure (min/day) and identify the level of concern.

The Results

We found that in some homes, cooking and stove use resulted in high concentrations of air pollution.   Figure 1 shows the number of minutes per day were over one of the health thresholds for the average home and the most polluted home in our study. In the worst, this home had more than two hours per day of unhealthy air! The most important pollutants were PM2.5 (from cooking, especially frying) and CO2 and NO2 from the gas stove or oven.   What were some homes much worse than others and what can be done about it? Certainly the amount of cooking matters, as does using a ventilation fan.  But we saw somewhat inconsistent results in the data with the use of ventilation fans.   

What’s Next

While the data we got from this study was a crucial first step toward understanding cooking with stoves/ovens and how it affects indoor air quality, there is still more to be done. Using low-cost sensors can help bring awareness to the levels of harmful pollutants produced in homes while cooking.  This awareness can lead to changes that reduce the number of pollutants that remain in your kitchen during cooking, whether that’s opening a window to improve air flow or investing in an air purifier for your kitchen.   Another solution would be to replace a gas stove or oven with an electric version, but at an average cost of $1,000-$3,000 and another $2,000-$3,000 for home electric modifications, this solution can be impractical and cost prohibitive. We will be conducting a new home study starting in September gain a better understanding of our previous results and see if we can determine what factors cause some homes to have higher concentrations of these pollutants than others.  Finally, we’ll be testing a commercial ozone scrubber to determine if it can reduce NO2 produced in homes during cooking.  Some preliminary tests are promising.

Want to participate?

Please read the following criteria to see if you’d be a good fit. You must:

  1. Have a gas stove and/or oven.
  2. Cook on a regular basis (at least 7 meals per week). This means at least some cooking done by stove or oven and cannot just be boiling water.
  3. Have Wi-Fi.
  4. Be willing to provide some information about your home such as general house layout (open concept vs contained rooms), room sizes, and ventilation.
  5. Be willing to record information on your cooking each day as accurately as possible.

If you think you’d be a good fit and would like to know more about how your cooking affects your indoor air quality, please submit a volunteer form. If you are selected for the study, we will send you a sensor package to put in your home for two weeks.  The sensor will connect through your Wi-Fi so we can access the data.  During the first week, participants will cook as normal and during week 2, all possible steps to reduce/mitigate indoor air pollutants should be taken. This could include running your stove fan, opening windows (box fans facing outside can be placed in windows to help increase removal), and/or using a HEPA air purifier. After the two weeks, the sensor will be returned to us so we can send it to other participants.  At the end of the study, we will send a report on the indoor air quality to the participants.

References

Ehlers, M. (2020). Gas Stove. Pexels. photograph. Retrieved from https://www.pexels.com/photo/gas-stove-3722212/.

Jacobson TA, Kler JS, Hernke MT, Braun RK, Meyer KC, Funk WE. 2019. Direct human health risks of increased atmospheric carbon dioxide. Nature Sustainability. 2(8):691–701. doi:https://doi.org/10.1038/s41893-019-0323-1. https://www.nature.com/articles/s41893-019-0323-1.

Nilsen RR. 2023 May 3. New York becomes the first state to ban natural gas stoves and furnaces in most new buildings. CNN. https://www.cnn.com/2023/05/03/us/new-york-natural-gas-ban-climate/index.html.

‌ Robertson S. 2024 Apr 2. New Washington state law does not “ban” natural gas, does discourage use. king5com. [accessed 2024 Jul 11]. https://www.king5.com/article/tech/science/environment/new-state-law-does-not-ban-natural-gas-discourages-use/281-04f7f343-1669-4e60-858c-18ff176c750a.