There's not a lot of natural gas drilling in Kentucky, but nearby West Virginia, Ohio and Pennsylvania have become hotbeds as the Marcellus Shale is tapped. Now, in response to a study, the Occupational Health and Safety Administration and the National Institute for Occupational Safety and Health are warning natural gas workers that they could be exposed to unhealthy levels of silica dust.

Silicosis is a lung disease caused by silica dust, and has long been associated with mining. But when natural gas workers fracture–or “frack”–the shale rock, they use large amounts of silica sand. As Elizabeth Grossman reports for public health blog The Pump Handle, that can cause major health problems too.

As reported previously by The Pump Handle, NIOSH’s recent investigation of silica exposure at fracking operations recorded many air samples with silica levels “above defined occupational exposure limits” for workers both directly and indirectly exposed to operations producing this dust. Given the serious health hazards posed by breathing silica dust, preventing these exposures is a matter of urgency.

Grossman says OSHA will be working over the next few weeks to notify industry groups of the hazard alert.