Erionite is a naturally occurring mineral that belongs to a group of silicate minerals called zeolites. It is usually found in volcanic ash that has been altered by weathering and ground water.

Calling erionite "an emerging North American hazard," the National Institue for Occupational Safety and Health (NIOSH) says a growing body of evidence links the substance to serious health effects includng lung disease.

Mesothelioma, an exceedingly rare and lethal form of cancer, was once thought to be caused only by inhaling asbestos fibers.