The 5 Best Things for Planet Since Earth Day Started

(April 22) -- From climate change to increased global air pollution, numerous challenges face the planet. But on the 40th anniversary Earth Day, AOL News asked two leading voices on the environment to reflect on the greatest triumphs of the past few decades.

Five events over the last 40 years stuck out as being the most important. The majority of them took place in the United States, which remains the world's largest consumer economy -- and, until recently, has been the world's biggest polluter. While future lists will surely contain events that transpire in China and other countries, and may include inventions such as hybrid or fuel-cell automobiles, the following five milestones have had singular impact when it comes to improving the quality of our world.

1. The Creation of the Environmental Protection Agency

In 1970, President Richard Nixon created a government agency whose mission was to oversee the nation's environment. "As America's cop on the beat, EPA was and is tremendously important for cleaning up our water and air," Josh Dorner, a spokesman for the Sierra Club, the nation's oldest environmental organization, told AOL News.

Since its inception, the EPA has overseen virtually every aspect of our nation's natural well being. Whether regulating lead paint, acid rain or the use of pesticides, the agency proudly states its mission as protecting "human health and the environment."

"Our economy is now three times larger than when the EPA was established," David Doniger, policy director of the Natural Resources Defense Council, told AOL News. "Over that same period, we have been able to cut pollution by 60 to 90 percent."

2. The 1970 Amendment to the Clean Air Act

The average human being breathes 20,000 liters of air every single day. Back in the late 1960s, despite the passage of the initial Clean Air Act of 1963, that air was distinctly less pleasant to inhale than it is today as it was filled with dangerous amounts of carbon monoxide, sulfur dioxide and lead.

In 1970, the U.S. Congress authorized the EPA to set air-quality standards that regulated the amount of hazardous gasses permissible in the nation's air. The results came very quickly.

"Blood lead levels of Americans fell by 50 percent by the 1980s," Doniger said. "And they've continued to drop even though we have more cars on the road."

3. Passage of the Clean Water Act

Enacted in 1972, the initial provisions of the Clean Water Act targeted American industry for its rampant pollution of the nation's waterways. As with the Clean Air Act, the EPA set targets for the amount of chemicals that could be introduced to a given body of water.

"In the 1970s in America we had rivers that caught on fire," Dorner said. "Corporations could dump whatever they wanted to into our lakes, rivers and oceans. The Clean Water Act has been a tremendous tool in giving Americans clean water in which to drink and recreate."



4. The Invention of the Catalytic Converter

While the Clean Air Act mandated that the United States eventually phase out leaded gasoline, the invention of the catalytic converter by Eugene Houdry made that goal much more attainable.

First, the catalytic converter paved the way for automobiles to run on unleaded gasoline. Second, the device reconfigures toxic byproducts produced by automobile engines into far less harmful gasses. With catalytic converters becoming standard in American automobiles, the country was able to phase out leaded gasoline by 1986. The average car fitted with a catalytic converter emits one-fifth as much pollution as those without them.

"There's no doubt the catalytic converter was important," Dorner said. "Especially in conjunction with the CAFE standards later introduced in Congress. Remember, in 1975, the average car got 12 miles to the gallon."

5. The Signing of the Montreal Protocol

In the 1980s scientists made a startling discovery: The ozone layer that protects the Earth from harmful ultraviolet radiation from the sun was thinning. The buildup of chlorofluorocarbon chemicals such as those found in aerosol cans in refrigerator coolant was determined to be the reason. The scientific consensus was that a public heath disaster loomed as skin cancer rates were expected to jump by hundreds of millions of cases.

"It is unspeakable how bad it would have been if we wouldn't have done anything," Doniger said.

But in 1987, the United Nations convened a conference at which several nations, including the United States, agreed to impose strict controls on the use of the chemicals. Today, every nation in the world has signed onto the agreement, and the depletion of the ozone layer has been halted.Gre