US environmental regulators reject Colorado's plan to clean up regional haze

US environmental regulators are partially rejecting Colorado's plan to reduce regional haze, which is air pollution that reduces visibility. The state's plan relied on closing some polluting facilities, but the regulators say the closures were not justified enough.

States must submit plans to clean up regional haze every few years. This decision means Colorado cannot rely on simply promising to close polluting facilities without a stronger legal basis. It sets a precedent that future state plans will need more concrete, enforceable commitments to reduce air pollution.