An analysis of EPA data finds that six Texas refineries reported benzene levels above the federal threshold for a one-year period that ended in September.
Three of the refineries are in the Houston area: Pasadena Refining, Shell Deer Park, and Marathon Galveston Bay Texas City.
Of the other three, one is in Port Arthur and two in Corpus Christi.
The rule requires refineries to collect air samples at their fence lines every two weeks, and to investigate and take action if emissions of the hazardous pollutant exceed a certain level for a year.