That accident comes after the publication earlier this week of a report by Congressional Democrats charging that oil and gas companies injected hundreds of millions of gallons of hazardous or carcinogenic chemicals into wells in more than 13 states between 2005 and 2009, as part of the fracking process.

The inquiry, initiated by the House Energy and Commerce Committee, which had been led until this year by Democrat and fracking critic Henry Waxman, also found that 14 of the country’s most active hydraulic fracturing companies had used 866 million gallons of fracking chemicals, not including water. Some 99% of the average fracking formula is water, but since a single frack job can use up to 5 million gallons of fluid, that still means tens of thousands of gallons of fracking chemicals.

Although industry allies criticized the report for lacking context, the inquiry found that 11.4 million gallons of fluid were injected that included at least one of the toxic group of chemicals: benzene, toluene, zylene and ethylbenzene. That doesn’t mean that any hazardous chemicals from fracking actually came into contact with groundwater supplies--indeed, the depth of most shale gas would make it unlikely--but that’s not absolutely certain, so limiting the use of toxic ingredients would be a pretty good idea.