Houston’s mayor is turning up the heat on petrochemical refiners and pressuring them to clean up their acts on air pollution.

Mayor Bill White won city council’s approval to sue two refining companies, Valero and Texas Petrochemical.

Meanwhile, he’s unveiled a voluntary plan under which he hopes industries will reduce their emissions of benzene.

That’s a carcinogen that escapes from refineries through everything from flares to tanks to transport pipes.

City officials say the biggest emitters of benzene are clustered around the Houston Ship Channel.

The mayor’s environmental experts note that a number of states regulate benzene levels but so far, Texas does not.