Oil spills, water pollution, harmful pesticides: those are the types of contaminants that spurred environmental crusaders to initiate the first Earth Day in 1970.
Damage from industries, businesses and agriculture was noticeable, from thick sludge in landfills that bordered homes to unnatural plumes of green smoke that were emitted from spraying farms. As Earth Day approaches its 42nd anniversary, what's potentially the biggest threat to the environment is as difficult to rally behind as it is to predict.
