Earth Day was invented 35 years ago at the beginning of the environmental movement. At the time, a lot of the country literally was a mess. For example, the tiny town of Philo, Ohio had a yellow haze hanging over it from the high-sulfur coal burned at the power plant across the river. Pittsburgh included air quality in weather forecasts in the mid-1970s and these seldom hit "acceptable". In 1969 an oil slick on the Cuyahoga River caught fire, tarnishing Cleveland's reputation for a generation. This wasn't even the first time the river had caught fire.
Since then, things have improved enormous. Car emissions have been cleaned up so much that the EPA is now looking at lawn mowers and chain saws in order to get further improvement.
The environmental movement is one of the great success stories on the late 20th century.
You wouldn't know if from the way that some people act. Typically for such movements, there is no need for exaggeration at the beginning. The facts are self-obvious. As the easy goals are met, the organizers are unwilling to admit victory. Instead they grow increasingly more hysterical. With no easily perceived targets eradicated, the environmentalists have moved on to Global Warming. This is big and scary. Since it is theoretical almost anything bad can be ascribed to it and it offers endless employment for environmentalists who want to turn society back to the stone age. An in-depth examination can be found in three parts here (part 1, part 2, part 3).
Environmentalists have been less than honest about the costs of preventing global warming (assuming it exists and can be stopped). Sites like this say that all we have to do is buy hybrid cars and switch electrical generation to other technologies and everything will be fine. This would help with the meaningless Kyoto goals but real change would require serious cutbacks affecting every aspect of life.
In 1990, there was a big interest in the environment. Earth Day's 20th anniversary became a major event. Ted Turner fed into this and starting that year, he produced a series of cartoons to "teach" kids how to be better residents of planet Earth. Called Captain Planet and the Planeteers, the show featured five teenagers, the earth spirit Gaia (voiced by Whoopi Goldberg), and Captain Planet himself, a blue superhero. (The kids represented the four elements plus "heart".)
The show went a step or two beyond propaganda. The kids were sent to stop polluters who always looked like some sort of ugly mutant. Pollution was never a byproduct of constructive activities, it was always an end in itself. Just to twist the knife a bit deeper, four of the kids were well versed in how to be earth-friendly. The exception was the American kid, the one the audience would most likely identify with. The Captain Planet web site describes him this way:
Wheeler is an impulsive, street-wise teenager from Brooklyn, always ready with a flip remark. He loves to provide comic relief to his fellow Planeteers and to goad the villains. Wheeler is the least knowledgeable Planeteer when it comes to ecology.
Although he sometimes fails to understand the issues at hand, his heart is in the right place. He fancies himself the "ladies' man" and flirts incessantly with Linka, the Planeteer from Eastern Europe.
This echoed a theory common within the ecological movement at the time - that western civilization had divorced itself from being in touch with nature and that all other civilizations are superior because of this.
Captain Planet, a poorly produced piece of propaganda, is emblematic of today's environmental movement. The Earth is represented as an intelligent goddess and no hard choices exist.
For more thoughts on the current state of environmetalism, see this response to the essay The Death of Environmentalism.