"Open train cars filled with sand have raised alarm in St. Paul's St. Anthony Park neighborhood, where some residents wonder if the silica that comprises 80 percent of the unprocessed sand is safe."
"The cars, which often are parked in a rail yard sandwiched between homes and an industrial zone, are appearing on a more regular basis since an oil boom has increased the demand for the sand for its hydrofracking operations.
BNSF Railway Co., which transports the sand, and Minnesota Commercial Railway representatives said the trains are carrying wet 'unprocessed raw sand' -- not pure frac sand -- and that it isn't a health risk. The concern, however, is that nearly all information about silica's health impact are derived from studies in the workplace, where it has been shown to cause cancer, and not of ambient exposure.
'We know it's [silica] not good for you,' said Hillary Carpentar, a toxicologist with the Minnesota Department of Health. 'It's a classic occupational toxin. I think the concern is that we just don't know' about casual exposure."
Chao Xiong reports for the Minneapolis Star Tribune June 27, 2012.