Lyrics by James Rado and Gerome Ragni in the off-Broadway debut of the musical "Hair" in October 1967 set the stage for one of the most powerful pieces of environmental legislation in U.S. history.

Welcome sulphur dioxide,
Hello carbon monoxide
The air, the air is everywhere
Breathe deep, while you sleep, breathe deep

Less than four years later, President Nixon signed the Clean Air Act and soon after that formed the U.S. Environmental Protection Agency to implement the landmark legislation.

On Sept. 14, EPA Administrator Lisa P. Jackson will mark the 40th anniversary of the Clean Air Act's passage at a Washington, D.C. conference. She'll be joined by "leading contributors who have helped shape the act over the past 40 years." The list includes politicians, private sector types and activists.

The real test is the air itself. I live in California's Central San Joaquin Valley, a hotbed of agriculture known for its brown, smog-filled skies. Allergy doctors do well here, and bad-air days are as common as rain in the Pacific Northwest.

Foul air settles in the Valley, which has very little wind and zero rain in summer. Reportedly, noxious emissions from the Bay Area and possibly as far away as China make their way to settle in scenic Fresno and the foothills of the Sierra Mountains.

Thursday's Air Quality Index rating by the San Joaquin Valley Air Pollution Control District showed a moderate 97 for Fresno County, and an "unhealthy for sensitive groups" 110 for Tulare County just to the south. Ratings below 50 are considered good.

Worldwide it's not much better. According to 350.org, our air has 390 parts per million of carbon dioxide and should have 350 ppm to be considered healthy. The organization has launched a campaign to reduce the amount through grassroots activities on Oct. 10.

Author and clean air activist Bill McKibben says even if we succeed on removing all the fossil fuel belching cars, factories and other contributors, we'll still see the globe warming for decades. He says our prospects are dour.

This comes despite positive moves in past years. Earthjustice.org argues that the amendments added to the Clean Air Act in 1990 gave the law the teeth it needed to go after polluters. "There is no better tool for cleaning up toxic air pollution," said Earthjustice attorney James Pew on the website.

Those amendments, by the way, were signed by President George H.W. Bush, who said at the time: "This bill means cleaner cars, cleaner power plants, cleaner factories and cleaner fuels; it means a cleaner America."

Eliminating the brown nasty air remains a huge challenge. While most of us prefer the smell of clean air (I recall the undeniable freshness after thunderstorms in Fairbanks, Alaska), we still want our cars, our houses at 76 degrees (or so) and the independence of urban and rural sprawl.

And everybody seems to have an opinion. A search for "clean air act importance" on Google turned up a post from the Nuclear Energy Institute that basically said: "Want to clean the air? Go nuclear." I paraphrase. However, the writer does have a point. Dealing with the political fallout and spent plutonium is another matter.

And some want status quo. There's the movement supporting Proposition 23 in California, which would roll back the state's Global Warming Solutions Act. Also known as AB 32, the act seeks to reduce greenhouse gas emissions in California to 1990 levels by 2020.

Needless to say, Prop. 23 wouldn't help clean the air. It's supported by Texas refiners Tesoro and Valero and just got a $1 million boost from Koch Industries, a company notorious for its anti-environmental stance. Rebecca Lefton called the trio the "toxic triplets" in a post on climateprogress.org.

The battle continues. Coal is in the sights of many environmental groups, and the industry is fighting back, trying to keep coal ash from being regulated as hazardous waste and keeping coal mines and coal-fired power plants operational. Of course, the argument there is that coal is domestic, in abundant supply and the industry offers massive employment in questionable times.

It's time for clean energy to step up. Many reports say the industry, such as it is, will generate millions of new jobs. Where are they?

Those interested in listening in on EPA's 40-year look-back event can see it webcast live at http://www.epa.gov/live/.

Photo: Rocky Mountains.