"One of the oldest known workplace dangers is breathing in tiny bits of silica, which is basically sand. Even the ancient Greeks knew that stone cutters got sick from breathing in dust. And today, nearly 2 million American workers are exposed to silica dust in jobs ranging from construction to manufacturing."
"The legal limit on how much silica workers can inhale was set decades ago. Workplace safety experts say that limit needs to be cut in half — because otherwise, workers face an increased risk of lung cancer, silicosis and other diseases.
And on Valentine's Day in 2011, it looked like a safety agency at the Department of Labor was getting ready to do that. The Occupational Safety and Health Administration (OSHA) sent a proposal for new silica rules to the White House Office of Management and Budget (OMB). The proposal was supposed to get a 90-day review. But almost two years later, it's still under review."
Nell Greenfieldboyce reports for NPR February 7, 2013.