While NRG disputes the claims, the Sierra Club study contends the W.A. Parish power plant in the small town of Thompsons is exceeding allowable sulfur dioxide emissions by more than twice the federal standard in its highest concentrations. By comparison, the Sierra Club said the plant’s pollution is equal to eight times the sulfur dioxide emitted by all the refineries in the Houston area combined. W.A. Parish is one of the state’s largest power plants.

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