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“You see anecdotal claims that natural gas development has a public health impact, but most of those claims have been refuted by investigations by state or federal regulatory agencies,” said John Krohn, a spokesman with Energy in Depth, a public outreach campaign of the Independent Petroleum Association of America.

Mr. Krohn argues that opponents of fossil-fuel use will use the public health argument — or whatever other argument seems best at the time — to discredit fracking.