When a workplace safety expert named Eric Esswein [with the National Institute for Occupational Safety and Health] got a chance to see fracking in action not too long ago, what he noticed was all the dust. The dust was coming off big machines used to haul around huge loads of sand. Sand is a critical part of the hydraulic fracturing method of oil and gas extraction...But sand is basically silica — and breathing in silica is one of the oldest known workplace dangers...[E]xposure to the tiny particles...sometimes lead[s] to serious lung diseases...Traditionally, silica exposure has been associated with jobs like mining, manufacturing and construction. But...some workers in the newly burgeoning fracking industry may be at risk, too...[A]bout a third of the air samples [Esswein and his colleagues] collected had such high levels of silica, that the type of respirators typically worn wouldn't offer enough protection...Government officials and the fracking industry say they're now working together to reduce workers' exposures. [refers to new, potentially safer technologies being tested by Encana]