According to this Mother Jones article, the drought in California is leading to increasing amounts of oil wastewater being applied to crops. While I understand and support programs like Bill Gates’ effort to extract potable H20 from sewage water as a means of preventing disease in poor countries, this would not be quite the same. Benzene, a known carcinogen, is showing up in concentrations higher than is allowed for drinking water. As an official comfortingly reassures us in the MoJo article:
“I admit that [some oilfield contaminants] are in there,” says David Ansolabehere, the General Manager of the Cawelo Water District, “but they are at such a low level I wouldn’t think they are doing any harm. But we are looking into that to make sure there isn’t any harm being done.”
The trouble is, testing methods are badly outdated — only recently have officials begun testing for a wider range of industrial chemicals, complicated by the fact that they tend to be trade secrets. Energy companies have a long history of claiming their chemical recipes are proprietary information. So how do scientists know what to test for?
More info on Think Progress.