Mr. Blackwell's Worst Polluting List No surprise: Pickup trucks and oversized SUVs scored the lowest on the U.S. EPA's latest ranking of vehicles based on tailpipe emissions. The list graded vehicles on a scale of 0 to 10. Large SUVs like BMW's X5 and General Motors' Hummer H2 earned a 0 and a 2, respectively, while most small and medium SUVs earned ...