In January 2023, comments made by a commissioner of the Federal Consumer Safety Products Commission (CSPC) sparked a debate that has left many worried they may have to switch out their gas cooking stoves for electric or induction models.
A Wall Street Journal opinion piece by Kim Strassel nicely summarizes the political and cultural battle that is ensuing, which appears to be well funded with several competing interests.
The impact of a ban on gas stoves would be profound. Thirty-seven percent of U.S. households rely on gas stoves, according to Consumer Reports, along with 76% of restaurants, according to the National Restaurant Association.
Why is this happening now?
An article published in the International Journal of Environmental Research and Public Health by the Rocky Mountain Institute (RMI) assumes that gas stoves used for cooking are “… associated with an increased risk of current asthma among children” and concludes that almost 13% of childhood asthma cases in the U.S. can be attributed to gas stove use.
The paper goes a step further to name the proportion of asthma cases that could be prevented in certain U.S. states (21% in Illinois, 20% in California, 19% in New York, 15% in Massachusetts, and 13% in Pennsylvania).
Dr. Anthony Cox of Cox Associates, and editor-in-chief of the journal, Risk Analysis, has authored a detailed critique that identifies many errors in the RMI study and sees it as a teaching opportunity. Currently under review at Global Epidemiology, hispaper states:
Systematically checking how and whether QRPs [questionable research practices] have been addressed before reporting or responding to claims that everyday exposures cause substantial harm to health might reduce social amplification of perceived risks based on QRPs and help to improve the credibility and trustworthiness of published epidemiological risk assessments.
Dr. Cox has also served on the faculty of the University of Colorado, is a member of the National Academy of Engineering,and a board member of the Center for Truth in Science.
While studying the effects of indoor air quality on children’s health is vitally important, there are far too many unanswered questions about the data in the RMI article — from the absence of details on total exposure and confounders, to a central question regarding causal evidence for gas stove emissions, particularly nitrogen dioxide, and childhood asthma.
The paper did not present any new evidence of a relationship between gas stove use and childhood asthma. Rather, it was a mathematical exercise that used existing (and estimated) data to calculate a theoretical Population Attributable Fraction.
This lack of context and clarity means there is no assurance that 13% of childhood asthma could be prevented by eliminating gas stove use, as the paper concluded.
What is harmful about gas appliances?
This question has been examined since the 1980s. Gas stoves produce small amounts of methane, nitrogen dioxide, formaldehyde, and small particulate matter (tiny particles or droplets in air that are two and one-half microns or less in width). Fine particulate matter, or PM2.5, results from all kinds of combustion, and has even been attributed to induction stoves.
The level of formaldehyde emissions from using gas stoves is very small. A 2014 study published in Environmental Health Perspectives found that the appliances added little to indoor formaldehyde concentrations relative to other indoor sources, such as furniture and building materials.
A majority of studies on the possible health effects of gas appliances, especially childhood asthma and respiratory diseases such as COPD in elder adults, have focused on nitrogen dioxide emissions from gas cooking. They are widely referenced in recent media stories that have proliferated about the dangers of using a gas stove, with many stating that nitrogen dioxide not only exacerbates the existing cases of asthma in children, but also causes it. A quick, yet fairly thorough, search of the literature found two reviews (a 2009 critical review and a 2013 meta-analysis). Despite the age of these papers, it appears most of the discussion surrounding gas stoves, including the latest paper published by RMI, rely on one or both of these reviews.
The 2009 critical review, published in Critical Reviews in Toxicology, was limited to human clinical studies of adverse health effects of short-term nitrous oxide exposures. The authors explain that the epidemiological literature at that time was inconsistent and uncertain due to many research errors (potential for exposure misclassification, residual confounding, co-pollutant effects), and reasoned that animal studies did a poor job of determining human-relevant doses.
They concluded that in over 50 experimental studies of humans inhaling nitrogen dioxide, there were no statistically significant changes in lung function and bronchial sensitivity with increasing concentrations of nitrogen dioxide. Any changes noted were mild and short-lived, reported effects were not consistently adverse, and symptoms were not dependent on increases in nitrogen dioxide. The authors concluded the results do not establish a mechanistic pathway leading to adverse health effects for short-term nitrogen dioxide exposures at levels in the ambient environment at that time. What this means for higher levels and longer exposure times is unclear.
The 2013 meta-analysis from the Institute for Risk Assessment in the Netherlands, examined 41 population studies published on specific effects associated with indoor nitrogen dioxide and gas cooking, and asthma and wheeze in children.
The Mayo Clinic defines “wheeze” as a high-pitched whistling sound made while breathing, and states it is often associated with difficulty breathing. It is distinct from asthma.
Interestingly, the authors found no association between indoor nitrogen dioxide levels and risk of asthma in children, but did find cooking with gas stoves increased risk of asthma. They also found that risk of wheeze increased with exposure to nitrogen dioxide emissions from gas stoves. They explain these findings as follows:
Gas cooking produces nitrogen dioxide and other pollutants, such as ultra fine particles [i.e. pm2.5]. Our finding of an association between gas cooking and asthma in the absence of an association between measured nitrogen dioxide and asthma suggests that gas cooking may act as a surrogate for causal variables other than air pollutants produced by gas combustion.
According to the EPA:
Particulate matter contains microscopic solids or liquid droplets that are so small that they can be inhaled and cause serious health problems. Some particles less than 10 micrometers in diameter can get deep into your lungs and some may even get into your bloodstream. Of these, particles less than 2.5 micrometers in diameter, also known as fine particles or PM2.5, pose the greatest risk to health.
Could PM2.5, or other fine particulate matter, be some of the causal variables of childhood asthma? This needs to be studied further before conclusions can be drawn. In the meantime, we should note that induction cooking also likely contributes to fine particulate matter indoors, as does any form of cooking, such as toaster ovens and electric ranges, according to a 2011 study of homes in California.
What about methane?
Methane is the most prominent emission from gas stoves, and was detected in a majority of homes in one Stanford study, even when the gas stoves were turned off. While methane is relevant to the issue of climate change, it is not toxic.
There is wide consensus on the need to reduce methane emissions from all sources to limit the impact on climate change. However, methane emissions from gas stoves account for a small portion of total methane emissions in the U.S., making reduction from other emission sources (e.g., oil, cars, landfills, agriculture, etc.) more of a climate change priority. Additionally, as of 2015, the most recent year with detailed data from the U.S. Energy Information Administration, gas stoves accounted for less than 3% of household natural gas use in the United States.
According to Wirecutter, “Switching from gas to a standard electric stove in 2021 might not even reduce your carbon emissions right away. It all depends on how your local grid generates the electricity that your new stove would use in place of natural gas.”
What happens if we stop cooking with gas?
There are safety questions surrounding the electromagnetic fields (EMFs) used by induction stoves, and potential health risks from this type of exposure. There have been links to cancer that must be explored further, along with some studies that have shown EMFs to be hazardous to pacemakers.
Individuals coerced into switching stoves, either by fear or by force, will be faced with higher costs, many of whom may not be able to afford the increase, even with current rebates being offered at the federal level. Special cookware is also necessary for induction stoves.
Other electric stoves are not as efficient as induction, and will add to more carbon emissions in the producing of electricity. There are calculators that compare the carbon footprints of stove types.
There are some low-income communities where gas stoves also serve as an emergency heat source when electricity is cut off, for both weather-related malfunctions and non-payment of electric bills. What will replace this needed (albeit unsafe) heat source until we can do better in supplying good, consistent residential heat to all communities?
Another issue that has not been mentioned in the discussion, is what to do with all of the gas stoves in working condition that are currently being used in households. Will the stoves and accompanying gear be added to landfills, a major source of methane emissions, if we rush to replace gas stoves?
More science is needed in the gas stove debate
This area of research has a lot of questions worth asking and answering:
- At what level, and for which individuals, do gas stoves really pose harm?
- Can gas stove use be made safe enough in terms of toxic emissions through better ventilation systems? Do we have existing technology to do this?
- Can gas leaks be mitigated with inspection and tightening of loose fittings?
- Can we more accurately identify the health issues at specific levels of exposure for individuals and families so that consumers have the information they need to make informed choices, without the use of scare tactics?
Ten years since the last meta-analysis is much too long. Methods for systematic reviews have improved during that time. Literature from human, animal, and epidemiological studies, including mechanistic exploration must all be considered in one review.
We are due for a well-done systematic review that synthesizes what we know, assesses the quality of existing studies, and identifies the next directions for research. There is also a need for better epidemiology (i.e., without questionable research practices) and additional causal analysis that, hopefully, uses advances in computational techniques and causal inference methods to determine cause more accurately.
This issue has ignited a firestorm, and it will be important to use good science to calm people down, separate facts from fear, and prioritize actions that are best for public health and the environment.