A construction site in San Mateo, Calif., earlier this month. There were 738 deaths of construction workers in the U.S. during 2011, the most of any single industry. The fatality rate per workers was higher, when taken together, in agriculture, forestry, fishing and hunting Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

A worker stands on top of a storage bin on July 27, 2011, at a drilling operation in Claysville, Pa. The dust is from powder mixed with water for hydraulic fracturing. Keith Srakocic/AP hide caption

itoggle caption Keith Srakocic/AP

A worker makes a cut in the side of a sandstone block at the Cleveland Quarries facility in Vermilion, Ohio, earlier this month. The legal limit on the amount of silica that workers can inhale was set decades ago. Ty Wright/Bloomberg via Getty Images hide caption

itoggle caption Ty Wright/Bloomberg via Getty Images

The Centers for Disease Control and Prevention says the accidental release of chlorine gas at a Tyson Food plant could have been prevented with better communication. April L Brown/AP hide caption

itoggle caption April L Brown/AP