AUSTIN, Texas (AP) — State environmental regulators say air quality continues to improve in the Southeast Texas petrochemical complex.

The Air Pollutant Watch List kept by the Texas Commission on Environmental Quality consists of Texas areas where levels of certain pollutants reached levels of concern.

A statement issued Thursday by the agency states that one air pollutant, 1,3-butadiene, has been removed two areas of concern in Houston and the Beaumont suburb of Port Neches. The statement says levels of the chemical have fallen 75 percent in Port Neches since 1996 and in Houston since 2004.

The agency statement also states that hydrogen sulfide has been removed from a third area of concern in Beaumont after its levels remained below state standards since 2005.