Epstein (2011) increase the true cost of coal several times over not the actual net cost public safety Epstein et al. (2011) externalities public safety externalities Skeptical Science previous examined public safety ignoring externalities "The True Cost of Coal Power" public safety article impact of burning fossil fuels on public health public safety Epstein et al. (2011) http://www.skepticalscience.com/true-cost-of-coal-power.html externalities The True Cost of Coal Power Skeptical Science previous examined Epstein (2011) Skeptical Science Skeptical Science: The True Cost of Coal Power costs of externalities