The new regulation prohibits spikes in emissions of substances like nitrogen oxides, sulfur dioxide and particulate matter. Image source: WikipediaThe new regulation prohibits spikes in emissions of substances like nitrogen oxides, sulfur dioxide and particulate matter. Image source: WikipediaA U.S Environmental Protection Agency (EPA) regulation unveiled in late May would roll back exemptions that 36 states have offered—some for years—to industrial facilities, allowing them to exceed without penalties or fines emission limits during startup, shutdown and malfunction periods.

The new regulation prohibits spikes in emissions of substances like nitrogen oxides, sulfur dioxide and particulate matter. The move represents a victory for environmentalists, who said the exemptions represented a major gap in protections afforded under the Clean Air Act (CAA).

The Sierra Club petitioned the EPA to make the change in 2011, arguing that the 36 states allowing the exemptions created an “affirmative defense” that is not allowed under the CAA. States with exemptions have until November 2016 to change them.

EPA says that, recent court decisions have held that under the CAA, such exemptions are not allowed in so-called State Implementation Plans (SIPs). Other court decisions have remanded similar exemptions in National Emissions Standards for Hazardous Air Pollutants (NESHAP), which the EPA says it is also correcting in separate actions.

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