Some workers at oil and gas sites where fracking occurs are routinely exposed to high levels of benzene, a colorless gas that can cause cancer, according to a study by NIOSH.

The agency recommends that workers limit their benzene exposure to an average of 0.1 of a part per million during their shift. But when NIOSH researchers measured the amount of airborne benzene that oil and gas workers were exposed to when they opened hatches atop tanks at well sites, 15 out of 17 samples were over that amount.

Workers must open these hatches to inspect the contents of these tanks, which could include oil, waste water or chemicals used in high-volume hydraulic fracturing, or fracking. The real-time readings taken by researchers show that benzene levels at the wells “reached concentrations that, depending on the length of exposure, potentially pose health risks for workers,” the researchers reported in the Journal of Occupational and Environmental Hygiene.

The study examined exposure risks for oil and gas workers during a phase of oil and gas extraction known as flowback. After a well is drilled in a tight geological formation such as shale and then hydraulically fractured to encourage the flow of hydrocarbons, fluids return up the well bore over the course of a month. The flowback contains fracking fluid, waste water, sand, oil and gas dissolved in water.  The liquids are separated into constituent substances, including valuable fracking chemicals that can be reused, oil and gas that are stored in production tanks, and waste fluids that are held in flowback tanks.

Workers measure the volume of liquids in flowback and production tanks by opening top hatches and inserting so-called gauging sticks into flowback tanks. If the tanks are very deep, workers use hand-cranked gauging tapes to make their measurements.

Researchers visited six oil and gas sites in Colorado and Wyoming in the spring and summer of 2013, spending about two days at each site. They outfitted 16 workers at flowback tanks with small devices attached to their shirt collars that sampled the air throughout the day. The key measurements were taken when these workers were standing above the hatch.

Over the course of a 12-hour shift, workers open the hatches and stand above them one to four times per hour, breathing in the fumes for two to five minutes each time. This could add up to dangerous levels of exposure to various volatile organic compounds from the chemicals used in fracking, or from the hydrocarbons themselves.

Source: The Los Angeles Times