Shouldn’t a peer-reviewed paper which purports to tie chemicals produced in the manufacture of natural gas (fracking etc.) to birth defects actually measure exposure (of fetus carriers, i.e. “mothers”) to those chemicals?
If you answered yes, you’ll never make it as an academic or government bureaucrat. Those folks know that successful careers are those which produce the most work for government.
As proof of this, take the peer-reviewed paper “Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado” in Environmental Health Perspectives by Lisa M. McKenzie and a slew of others, each of whom relies for their living on government.
Yet curiously, in a front page statement of “Competing Financial Interests”, those authors “declare they have no competing financial interests.”
It’s a side point, but all authors who rely on the increase and status of government should and must declare a conflict of interest just as authors who work for industry do. (More on this another day.)
Back to McKenzie. Here’s how Think Progress summarized her findings: Preliminary Studies Show Potential Health Risk For Babies Born Near Fracking Sites.
Preliminary, potential, risk. Who said science is political?
McKenzie was interested in the causes of congenital heart defects, neural tube defects, oral clefts, preterm birth, and term low birth weight. Besides naturally occurring genetic defects and defects caused by maternal folate deficiency, smoking drunkness and drug use, and other such things, it is suspected that exposure to benzene, toluene, polycyclic aromatic hydrocarbons, and petroleum based solvents might also cause congenital birth defects.
Here’s the winning phrase from the paper: “Many of these air pollutants are emitted during development and production of natural gas (referred to herein as NGD) and concerns have been raised that they may increase risk of adverse birth outcomes and other health effects” (and she cites herself as a source for this assertion).
Many of these pollutants are emitted? Okay, I’ll bite. Which? Which exact pollutants were the women in her study exposed to, and at what concentrations?
Answer: McKenzie doesn’t know. Nobody does. The epidemiologist fallacy has struck again.
The best she could do was to measure how far from a well location each mother lived at the time of birth. Where were those mothers before birth? Same addresses? Did they spend most of their pregnancy near the wells or away on vacation? What genetic characteristics did the people who lived near gas wells have that people who lived near the country club do not? How many women were drunks or druggies?
Answer: McKenzie doesn’t know. Nobody does.
McKenzie arbitrarily (to us readers, anyway) picked a 10-miles radius to label mothers “exposed”—to what, always remember, we don’t know. But doesn’t saying “exposed” sound scary? And being “exposed” to a mere gas well can’t hurt you unless you stub your toe on one.
And then came the wee p-values.
But not before manipulating the data in order to get it to work. Inexplicably, McKenzie divided living-near-gas-wells (what she called “exposure”) into terciles.
Unfortunately for headline hunters—I’m still amazed Think Progress missed this—wee p-values were found for decreased risk of low birth weight and preterm birth. Why did we not see in large print “Exposure To Fracking Reduces Low-Birth-Weight Babies”?
Or maybe the mothers who live away from the country club are younger and eat more heartily? Nah.
Another oopsie: oral clefts also appear to decline in frequency for some “exposed” women. So says a wee p-value. And no go for neural tube defects or congenital heart defects for the majority of “exposed” women. No go in the sense of no wee p-values for the “exposed”.
Only those in the highest arbitrary tercile evinced wee p-values (and small effects) for congenital and tube defects. Yet we have to ask which method McKenzie used to correct for the multiple statistical testing she did, i.e. all the hunting for signals. Well, you know the answer.
“Still, Briggs, what about those high terciles? Even if McKenzie manipulated the data, isn’t there something there?”
You’re forgetting that McKenzie never measured exposure to anything, but only distance from listed home residence to gas wells, and that some of her analysis showed benefits from this “exposure.” And since this isn’t real exposure, we have to adjust the analysis to account for the uncertainty of substituting addresses for exposure to unknown chemicals. Once that is done, the wee p-values would almost certainly swell past publishable size.
There is nothing but surmise, conjecture, wishful thinking in papers like this. Believing that fracking is bad for babies based on this paper is like convicting an accused murderer simply because he lived near the victim.