By Laura Arenschield
The Columbus Dispatch • Saturday September 13, 2014 6:35 AM
Oil and natural-gas workers on fracking sites are exposed to potentially unsafe levels of benzene, a colorless gas that can cause cancer, according to a case study by a federal agency.
The study, first published at the end of August in the Journal of Occupational and Environmental Hygiene, found that workers on oil and gas sites were most likely to be exposed to the chemical when they opened hatches during a phase of fracking known as “flowback.”
The study by the National Institute for Occupational Safety and Health, part of the Centers for Disease Control and Prevention, is preliminary, but it is part of an effort by the institute to understand the health risks of fracking. The technique is being used increasingly to extract oil and gas from shale that’s deep underground.
“It was more or less to demonstrate that even though you’re outside, there is still a potential” for exposure, said John Snawder, a toxicologist with the CDC in Cincinnati and a co-author of the study.
Benzene, a chemical that occurs naturally in oil and gasoline, attacks cells that affect blood and bone marrow. It can cause leukemia and anemia.
Flowback happens after a well is drilled. Drillers use a mixture of water, sand and chemicals to fracture, or “frack,” shale formations underground, releasing oil and natural gas trapped there.
After the shale is fractured, water, fracking fluid, sand, oil and gas flow back up the well to the surface, where the parts are separated. Wastewater frequently gets pumped into injection wells for disposal, fracking fluid gets reused if possible, and oil and gas are separated to be used for energy.
Oil and gas workers measure the volume of those flowback liquids by opening hatches on top of wells and inserting gauges. When they open the hatches, workers are exposed to the benzene that escapes into the air, researchers say.