well, i can help you get started:
- probably started with Teddy Roosevelt's conservation efforts, and cleaning up meatpacking industry - like that book The Jungle
- Got into high gear in the 1970s - I think that's when the EPA was established and the Clean Air Act or something...
- Al Gore and an inconvenient truth
-gas consumption
-controversy over ethanol
-controversy over whether global warming actually exists
-increasingly industrialized countries (india, china) not concerned about environmental issues
these are just some thought points to get you started... I hope it helps. good luck on your assignment