The Washington, D.C.-based Environmental Defense Fund (EDF) has released a state-by-state oil refinery ranking based on greatest pollution per barrel of crude oil processed. Among states with four or more refineries, Texas, Oklahoma, Montana, and Wyoming facilities emit the most pollution. Refineries in New Jersey, which has strict chemical reporting requirements, performed best. Also performing well were California, Ohio, and Washington. Oil refineries use and release toxic chemicals, sulfur compounds that create odors and cause acid rain, and volatile organic chemicals that contribute to smog formation. To create the rankings, EDF used publicly reported data for these pollutants to determine the pollution per barrel of oil refined. EDF then identified which of the country's 144 refineries with complete pollution data performed the best and worst for these multiple measures of refinery efficiency.