Madsen, Travis et al. Frontier Group and PennEnvironment. Research and Policy Center. “In the Shadow of the Marcellus Boom.”: How Shale Gas Extraction Puts Vulnerable Pennsylvanians at Risk.” May 2011.

The study examined Pennsylvania’s more than 3,000 gas fracking wells and found permitted well sites within two miles of 320 day care centers, 67 schools and nine hospitals.