A major polluter is at work these days, just as it is every year about this time, but as usual you won't hear a peep about it from the people involved in the environmental movement.

The polluter is autumn. Autumn to the "new environmentalists," as I call them (more on that later), is pure magic; its gorgeous hues have no more to do with pollution than a mirage, a rainbow or a holographic image formed in thin air.

There are others who think they know better. The people who live in the Great Smoky Mountains know that the haze that nearly always hangs above them, and often gets worse during certain days in October, does not come from their scattered whiskey stills, but somehow is caused by all those trees. They know that even those gorgeous hues of October have a dark side.

You see, the chemists have taken apart the reds, golds, purples and browns of the maples, beeches, birches, dogwoods and sumacs that make October the loveliest month of the year. When they finished, they had shown that every color present is caused by a chemical -- no better and no worse than the ones they make in their own laboratories and factories. So the hues of autumn are not at all like mirages, rainbows and holograms. Every one is a solid substance.

For example, the riboflavin that helps color the leaves of the tulip poplar yellow is a complex chemical complete with benzene and diazene rings, dangling methyl groups, and alcohol and ketone structures. And so it is with the flavones and carotenoids, which also add gold to the leaves, and the peonidins and pelargonidins, which give those brilliant reds and dusty purples to the leaves of the gum, dogwood and sumac.

These chemical pigments are there in vast quantities. The leaves that fall on New Hampshire alone contain enough pigments to color the paint required to cover every building in New York City and Chicago -- two coats. However, so far no simple method for extracting these pigments has been found. It is cheaper to make paint pigments in the pots and vats of the chemists, so those in the leaves are left to Mother Nature and the oxygen, ozone and sunlight that she uses to chew them up.

Maples, with their brilliant reds and yellows, probably do more than any other tree to add to the glories of autumn, while oaks, whose leaves are mostly dull brown, do the least. But what the oaks lack in brilliance they make up for in useful pollution. When oak leaves decay, they leave a richer deposit of tannic acid than any other leaf, and this acidity is much cherished by rhododendrons in the mountains of the southern states.

Now for the matter of what I call the "new environmentalists." I contrast them to the "old environmentalists," among whom I number myself, a dirty- handed crew of ranchers, farmers, botanists, chemists and others of that ilk. They know that while the Earth appears fragile, it really is tough and resilient. Also, they are not sure what the ideal shape is anyway. The new environmentalists believe they know what a perfect world should look like. One of their most cherished beliefs is that the air and waters of "Spaceship Earth" were once of pristine purity and could become so again if the human race didn't insist on messing things up.

Last October, one such new environmentalist returned to Philadelphia from a visit to his cottage in the Pocono Mountains and declared that pollution from New York City had finally reached his vacation retreat.

"We had a blue haze," he said, "which covered the whole area and reminded me of New York City, where it all probably came from. I think we ought to shut that place down."

New York City does produce more pollution than it should, and some of it probably spills over into other places, but this time the Big Apple was innocent. The leaves in the Poconos were falling fast and releasing perhaps as much ethylene gas as comes from a big oil refinery flare stack when the fire goes out. In addition, the benzene and terpenes from the evergreens, and the volatile aromatics from the decaying leaves already on the ground were all doing their bit to add to the smog that day. So if Mother Nature frowned and darkened the sky for awhile it is understandable why she did so. But she cleaned up the mess in a few days, as she has been doing for countless thousands of years.

In fact, the amount of natural pollutants that nature cleans up each year is astounding. It has been estimated that nature disposes of about 875 billion pounds of volatile organic chemicals from plant life each year. The amount of non-volatile plant products would, of course, be many thousand times as great.

Confronted with such facts, the new environmentalists ignore them or say: "Yes, but these things are natural products and therefore not harmful to life." They forget that strychnine is a natural chemical and so was the conine in that glass of hemlock that killed Socrates.

Ronald Reagan referred to some of these things in one of his 1980 campaign speeches, and the new environmentalists promptly declared he was afraid of "killer trees" and probably would have them all cut down if he got elected. Reagan's entire argument was quite to the contrary, but he wisely never returned to the subject because he knew the new environmentalists were not interested in facts.

This kind of behavior irks some of us old environmentalists who think that the dirty-handed ranchers, farmers, miners and oil-well drillers should be allowed to have reasonable operating room and be permitted to kick up some dust in going about their essential work.

Nevertheless, every October I think I may desert the ranks of the old environmentalists and join forces with the new breed. If I do so, it will be forrreasons of charm. It seems to me that some of the new environmentalists are bright and interesting people, and beyond all doubt the world they see is a more charming one than the world the old environmentalists have been struggling with so many years. Why shouldn't everyone believe that Jack Frost paints those gorgeous hues of autumn with his magical tints which vanish as mysteriously as they appear -- without even one speck of pollution?