Junk Science Again: This Time, Gas Stoves

There was an attempt to run the news cycle that started early this week with an attack on gas stoves.  It didn't seem to go as well as they wanted, but it could just be the early stages.  The immediate reactions, including memes and bumper sticker sayings and so on may have been more counter than they expected and it may have been exactly what they wanted; not being insiders we can never know.  

What we can know is that this is the level of so-called science that makes "climate change" seem as well-established as knowing when we drop something it'll fall.  

To begin with, this is not a new idea or a new discovery.  The article it was based on may have been a recent publication but the idea has been floated around for a while and just isn't that good.  To begin with I'm going to copy the abstract from that published article and point out some things. 

Indoor gas stove use for cooking is associated with an increased risk of current asthma among children and is prevalent in 35% of households in the United States (US). The population-level implications of gas cooking are largely unrecognized. We quantified the population attributable fraction (PAF) for gas stove use and current childhood asthma in the US. Effect sizes previously reported by meta-analyses for current asthma (Odds Ratio = 1.34, 95% Confidence Interval (CI) = 1.12–1.57) were utilized in the PAF estimations. The proportion of children (<18 years old) exposed to gas stoves was obtained from the American Housing Survey for the US, and states with available data (n = 9). We found that 12.7% (95% CI = 6.3–19.3%) of current childhood asthma in the US is attributable to gas stove use. The proportion of childhood asthma that could be theoretically prevented if gas stove use was not present (e.g., state-specific PAFs) varied by state (Illinois = 21.1%; California = 20.1%; New York = 18.8%; Massachusetts = 15.4%; Pennsylvania = 13.5%).

As always, this is based on an observation and correlation study, not a study in which every possible variable was controlled for except the one being studied and people were assigned at random to the experimental or control groups who had no way of knowing which group they were in.  That sort of test is very hard and expensive to do, as well as potentially being illegal or immoral, since you're doing something to people that you think could hurt them.  

The yellow highlighted word is very important. A meta-analysis (singular) is when a group of studies are combined to enlarge the data set.  The way this is worded implies this is a meta-analysis of a group of existing meta-analyses (plural).  That means that without extraordinary effort to ensure the studies are as identical as possible; not just that they studied the same thing but that the populations being studied were as similar as possible.  In turn, that means an increase in the chance of having some outcome could have as much to do with variations in the populations, locations, or any other uncontrolled variable as the presence of the thing they're correlating to.  They conclude, for example, " We found that 12.7% of current childhood asthma in the US is attributable to gas stove use."  In a meta-analysis of meta-analyses that's pretty much meaningless.  

When I took statistics, we were taught that a meta-analysis was typically less reliable than any one of the studies it was based on because it’s generally all but impossible to determine how well those groups compare on the countless other confounding factors.  I consider what this story is based on to be insignificant findings, regardless of their P value. I ignore those studies until the relative risk gets into the "more than twice as likely" range, that is, instead of this 1.127 risk ratio, it should be over 2.00. 

But it's even worse than that.  

About a year ago, a similar attempt to get people to dump their gas stoves was run, and was written about on Watts Up With That.  There were things in the study that really stood out as bad ways to do a study like this. 

Meanwhile, another expert told a different media outlet that the researchers had encased the kitchens in a Mylar tent to “trap and concentrate the emissions, and then measure the concentration.” No one cooks in a kitchen like that! He said it would “incorrect” to draw any health conclusions from the paper.

From Michael P. Ramirez.com 

As always when this sort of subject is talked about, there's no mention of the fact that if you have an electric stove it's very likely to be gas-powered, or even coal-powered. It's just that the gas isn't in your home, it's "far away" so it's different; they'll worry about that gas causing asthma next week. In reality, the truth is that they're just trying to get rid of natural gas power for anything anywhere.