Bromides, a salt found in brine from oil and gas drilling, create a carcinogen called trihalomethanes when they are chlorinated in drinking water. It is because of high levels of bromides in source rivers, such as the Ohio and Monongahela, that dozens of drinking water treatment plants in West Virginia and Pennsylvania have violated EPA standards for trihalomethanes since 2008– the year gas drillers began flocking to the area to tap the Marcellus Shale.
Since this spring, drillers have been sending less of their brine water from shale gas wells to municipal treatment plants, which do not have the expensive new technology required to remove bromides. They’re opting to send it to deep injection wells or recycling facilites instead. Thus, one would expect that, especially after such a wet year, bromide levels in the rivers would have dropped.
However, a story from Pittsburgh Public Media reports that bromide levels remain high. One potential culprit is conventional oil and gas drilling, but a definitive answer has not been found yet. The EPA plans to tighten standards for trihalomethanes in the spring, meaning that if drinking water treatment plants exceed standards for the chemical, its customers will be notified that their drinking water does not comply with the Safe Drinking Water Act.