A new Gradient report takes a closer look at recent research from RMI claiming 12 percent of childhood asthma cases can be linked to gas stoves, calling attention to numerous flaws in the study.
The Gradient report – which was commissioned by the American Gas Association – calls attention to the “miscalculations and misinterpretations” of population attributable factions (PAF) in scientific literature that have been cited in news articles and by government officials in their support of natural gas bans.
Here are three important facts about RMI’s study:
Fact: RMI disregards the lack of an established causal relationship.
According to Gradient, a valid PAF has a key underlying assumption that:
“[T]here exists an established causal relationship between the exposure and health outcome of interest. In the case of gas cooking exposure and childhood asthma, a causal relationship is not supported by the epidemiology literature.”
RMI failed to establish a causal relationship in its PAF study – a fact that an author of the study later admitted. As the Washington Examiner reported:
“Responding to a request for comment, RMI manager Brady Seals told the Washington Examiner in an email Wednesday that the think tank’s study ‘does not assume or estimate a causal relationship’ between childhood asthma and natural gas stoves.” (emphasis added)
.@RockyMtnInst finally stated that the paper doesn’t show a causal relationship between gas stove use and asthma. The attacks on gas stoves rely on reports that didn’t test #natgas stoves and omit studies that found no connection between them and asthma. https://t.co/BRLeWZxbLk pic.twitter.com/pc6sXZ7Lwc
— AGA (@aga_naturalgas) January 13, 2023
Fact: RMI overlooked biases in the underlying risk estimate
Gradient’s new report explains that “virtually all epidemiology risk estimates are subject to biases,” which can be carried over through the meta-analysis – a statistical combination of the results of multiple studies addressing a similar research question – that RMI used to reach their conclusion. The report continues that the RMI study did not address the potential biases in their PAF estimations inherit in their meta-analysis, stating:
“[T]he meta-OR that [RMI’s] PAF was calculated from was subject to not only publication bias but also biases that were common among the contributing individual studies, primarily due to exposure measurement error, reverse causation, confounding, and selection bias.”
In a systemic review of studies claiming to demonstrate a causal relationship between gas cooking and asthma, also commissioned by the American Gas Association and authored by Gradient, authors found the studies to be of low quality, stating:
“A large proportion of the studies to date are subject to multiple sources of bias and inaccuracy, primarily due to self-reported gas cooking exposure or respiratory outcome, insufficient adjustments for key confounders (e.g., environmental tobacco smoke, family history of asthma or allergies, socioeconomic status or home environment) and unestablished temporality.”
Fact: RMI overinterpreted the public health implications of PAFs
Gradient explains that:
“It has long been recognized that even a correctly-calculated PAF has limited, hypothetical meaning, due especially to the underlying assumptions often not being met (e.g., a causal relationship has not been established) and the fact that it is not linked to any well-defined, realistic intervention. Still, PAFs are often overinterpreted in the literature by epidemiologists as having real-world public health implications.” (emphasis added)
So while the RMI study and other similar studies are presented in headlines as having found a smoking gun, in reality, the studies aren’t actually measuring the exposure and concentration levels of pollutants necessary to establish valid health risks that reflect the headlines.
Gradient continues that RMI’s PAF estimates were not linked to any “mitigation strategies,” despite the RMI study’s conclusion acknowledging that known “mitigation strategies will lessen childhood asthma burden from gas stoves.” The Gradient report further notes that RMI’s failure to include these strategies in their calculations has contributed to an overinterpretation of the study’s health impacts.
Bottom Line
Gradient’s new report examining the population attributable faction used in RMI’s study explains how RMI’s findings are underwhelming and inaccurate. RMI’s tagline that 12 percent of childhood asthma cases are caused by gas stoves relies on misattributions of PAF to draw a conclusion that failed to include mitigation strategies, compounds the flaws in existing scientific studies to lend the conclusion credibility, and wildly overstates the health dangers.
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