The deaths of four oilfield workers since 2010 have prompted NIOSH to ask oil and gas firms to help the agency assess the health hazards associated with hydraulic fracturing.
In a May 19 blog post, NIOSH officials point to four worker deaths at well sites in the Williston Basin in North Dakota and Montana that might have occurred as a result of “acute chemical exposures during flowback operations.” Flowback, the agency explains, “refers to process fluids from the wellbore that return to the surface and are collected after hydraulic fracturing is completed.”
“While not all of these investigations are complete, available information suggests that these cases involved workers who were gauging flowback or production tanks or involved in transferring flowback fluids at the well site,” NIOSH officials wrote in the blog post. “Often these fatalities occurred when the workers were performing their duties alone.”
While safety hazards in the oil and gas extraction industry are well-known, the agency acknowledges that “there is very little published data regarding occupational health hazards (e.g., types and magnitude of risks for chemical exposures) during oil and gas extraction operations.”
“To address the lack of information, NIOSH requests assistance from oil and gas stakeholders in further characterizing risks for chemical exposures during flowback operations and, as needed, develop and implement exposure controls,” NIOSH officials wrote.
Fluids returned during flowback operations contain volatile hydrocarbons, NIOSH explains. Liquid hydrocarbons from the separation process are routed to production tanks, where workers periodically monitor the fluid levels with handheld gauges (sticks and tapes) through access hatches located on the tops of the tanks.
While exposure to hydrogen sulfide – also known as “sour gas” – is a well-recognized hazard in oil and gas extraction, NIOSH asserts that many of the chemicals found in volatile hydrocarbons are acutely toxic at high concentrations. Volatile hydrocarbons can affect the eyes, breathing and the nervous system, and at high concentrations also can cause abnormal heart rhythms, according to the agency.
Reducing Potential Exposures
NIOSH said its researchers have developed preliminary recommendations to reduce the potential for occupational exposures:
- Develop alternative tank-gauging procedures so workers do not have to routinely open hatches on the tops of the tanks and manually gauge liquid levels.
- Provide hazard awareness training to ensure that flowback technicians, water haulers and drivers understand the potential hazards and risks for volatile chemical exposures when working on and around flowback and production tanks.
- Monitor workers to determine their exposure to volatile hydrocarbons and other contaminants. Employers should consult with an occupational safety and health professional trained in industrial hygiene to ensure an appropriate sampling strategy is used.
- Ensure that workers do not work alone in potentially hazardous areas.
- Use appropriate respiratory protection in areas where potentially high concentrations of volatile hydrocarbons can occur as an interim measure until engineering controls are implemented. Employers should consult with an occupational safety and health professional trained in industrial hygiene to determine the appropriate respirator to be used.
- Establish emergency procedures to provide medical response in the event of an incident.
NIOSH noted that it has conducted exposure assessments to identify chemical hazards to workers involved in flowback operations.
“Results from initial field studies suggest that certain flowback operations/activities can result in elevated concentrations of volatile hydrocarbons in the work environment that could be acute exposure hazards,” the agency said.