People in Pennsylvania have been hearing about the environmental dangers of fracking for some time, but few realize that the danger for workers is not limited to eco-damage. A dangerous type of workplace injury in fracking operations is the penetration of lung tissue by fine sand particles called silica. This can lead to an incurable disease known as silicosis. It may also lead to lung cancer.The National Institute for Occupational Safety and Health or NIOSH recently conducted a study that involves 11 fracking sites in Pennsylvania and other states. At each of the sites, the researchers found elevated levels of silica in the atmosphere, and 79 percent of these levels exceeded established safety standards. At every site, workers wore respirators, but the researchers were concerned that silica levels were so high at one-third of the sites that the types of respirators in use would not provide enough protection for employees.