NASCAR is not the most green sport in the universe, efforts to be more environmentally friendly notwithstanding. It's dozens of cars whipping around a track, burning fuel as fast as possible to move pistons. Very few hippies attend races.
ThinkProgress assessed the sport's environmental footprint last month. Their calculations suggest that one race uses 6,000 gallons of fuel, emitting 120,000 pounds of CO2. That's in addition to the eight to 10 sets of tires each of the 40 teams use and the oil in the engines. Hell, until 2007, NASCAR used leaded gasoline. (To the sport's credit, they are increasingly using slightly-more-environmentally friendly ethanol in their fuel.)
Dale Earnhardt Jr. is one of NASCAR's top drivers. He's a legacy in the sport; his father was killed in a crash at Daytona in 2001. Over the course of his career, Junior (as he's called) has raced 455 times -- meaning he alone can be credited with about 1.36 million pounds of CO2 just on the track. And that's not to mention the other emissions from burning fuel: particulates and contributors to smog. Dale Earnhardt Jr. is not exactly a champion of air quality.