There's now a growing movement seeking to "green" this kind of event by making it more sustainable.

Not as visible, but equally or even more troublesome, is the impact of people traveling to the big events. With Greener Races, Athletes Try to Tread Lightly on the Earth Run a marathon or finish a triathlon, and your first thought may be "I can't believe I did it." Look back at the course behind you, and your second may be "Holy Nike, look at all the trash on the road!" Between the paper cups, plastic bottles, energy bar wrappers, and even those post-race foil blankets, these popular events produce a whole lot of waste. ReSport, as the Council for Responsible Sport is known, has developed a list of standards for races based on criteria such as waste handling, climate impact, and the materials used in finishers' awards and T-shirts. The Council for Responsible Sport estimates that the athletes participating in the 2007 Ironman World Championship in Hawaii produced greenhouse gases equivalent to the yearly carbon footprint of 972 average U.S. Depending on how much event organizers do, events can be certified at four different levels.

ReSport executive director and cofounder Khalil Vite says there is a "growing sensibility that races could do.