Like so many controversial topics, it is hard to get good information on fracking. Participants from both sides of the debate are prone to exaggeration and cherry-picking. Pro-frackers pretend there is absolutely nothing to worry about, and anti-frackers pretend that tectonic plates will rip apart and the Earth will deflate. The truth is undoubtedly somewhere in the middle.
One of the main concerns is the presence of methane in drinking water. Infamously (and dishonestly) portrayed in the "documentary" Gasland, a guy in Colorado lights his tap water on fire. Gasp! It must be because of fracking. But it wasn't. The methane in his tap water seeped there naturally by a process called methane migration. (Perhaps Gasland Part II will correct the record.)
Alas, a new study in PNAS shows that, indeed, fracking can increase the amount of methane in your drinking water. Scientifically dubious activist websites, such as Desmogblog, are already touting the study as a "damning" indictment against fracking. Is it?
The authors sampled well water and plotted the amount of methane in the water (y-axis) as a function of the distance in kilometers (x-axis) from a gas well. (See chart.) As shown, the closer a well is to a fracking site, the more likely it is to have a higher methane concentration.
Should this worry us? Not really. Most wells had methane levels that were far below the "action level" recommended by the US Department of the Interior. And, as just mentioned, methane naturally contaminates groundwater all the time.
Besides, there's another big point to consider, and almost nobody ever does: What level of methane contamination is actually dangerous?
Methane is non-toxic, but it is explosive. And, at very high concentrations, it can cause death by asphyxiation (since there isn't enough oxygen to get to your lungs). In the chart, the worst sample had 70 mg of methane per liter of drinking water. Can we expect the residents in this house to choke and then explode in a huge burning ball of flames?
Using a little chemistry and some simplifying assumptions, a fairly basic calculation can be performed. First, we need to know what percentage of the air in their house would contain methane. For the sake of argument, let's assume the worst: All 70 mg of methane (CH4) per liter of water escape into the air. And, the average American family of four uses 400 gallons (1514 L) of water per day.