While the lab remains the home of most scientific experiments, James G. Anderson's most important experiments take place more than 30 miles in the air.

Anderson's business is flying balloons--most more than 100 times the size of the Good year Blimp--an activity which has won him a reputation as one of the world's top experts in atmospheric chemistry. And in doing so, he has found himself at the heart of one of today's most pressing environmental questions.

In recent years, scientists, government officials and the public have become increasingly concerned that man-made and natural chemicals are destroying the ozone layer, the portion of the atmosphere that protects the earth from the sun's deadly ultraviolet radiation.

As a result, Anderson's expertise is in high demand, and he has answered the call with a series of innovative experiments. In the process, he has become the first person ever to successfully examine the stratosphere, a region too high for airplanes and too low for satellites to explore.

Anderson, a native of Spokane, says he has always had a fascination for balloons, but in the wheatlands of eastern Washington balloon flying was hardly the rage. He studied economics and then political science, but the science bug bit him, and before long he was off to pursue a career in atmospheric chemistry.

Only after graduating from the University of Washington at Seattle did he conduct his first high altitude experiments. While working on his doctorate in physics at the University of of Colorado, he began experimenting with sending rockets into the atmosphere. His balloons didn't enter the picture until he became an assistant professor at the University of Pittsburg, and by the time he landed at Harvard, he was a seasoned veteran.

In his efforts to learn the chemical compositions of the stratosphere. Anderson has become the the first person ever to actually conduct experiments in the mysterious region. After constructing highly sensitive equipment at his Oxford St. lab, he and his crew travel down the National Scienific Balloon Facility in the heart of the cowfields of Palestine, Texas. There they carefully assemble and load up unmanned balloons--which when inflated reach the the same height as Boston's John Hancock tower--with equipment that will measure the gas composition of the stratosphere.

Ozone, a highly unstable union of three oxygen atoms, provides the vital function of absorbing most of the sun's ultraviolet radiation. It is continuously being formed in the stratosphere, when regular oxygen molecules interact with ultraviolet radiation.

Life without ozone could not exist, as large amounts of low-energy ultraviolet radiation would pass freely to the ground. Such radiation could damage plants, reduce crop yields, promote skin cancer, and induce cataract-related blindness in all land animals.

Nature has provided just the right level of ozone for life; if one could squish all of the stuff in the stratosphere, it would amount to a strip of gas about an eighth of an inch thick. The danger is that various man-made gasses may be seeping up into the stratosphere and destroying this delicate balance, causing ozone to be eaten up faster than it is being made.

Scientists believe that fluorocarbons used in aerosol propellants, refrigeration fluids, fillers for synthetic foams, and electronic parts cleaners are capable of doing the most damage. In addition, gasses produced by burning coals or using artificial fertilizer are also thought to be dangerous.

These substances float up into the stratosphere, where they are broken up into molecules of fluoride and chlorine. And chlorine, which is known as a "free radical," is very bad for ozone; when the substances mix, ozone is broken down.

The stuff does not have to be entirely destroyed to be threatening. Anderson says if the amount of atmospheric ozone drops by as little as 10 percent, enough ultra-violet radiation could probably seep through to be "extremely serious," and if it dropped by 50 percent, it would prove devastating.

While scientists know that man's activity is destroying the ozone layer, there is little consensus over the extent of the damage, and over whether drastic steps are in order.

"Potentially, there is a very big problem, but concern is still premature," says George M. Whitesides, professor of chemistry. "The basic scientific knowledge is not there yet."

This is where Anderson and his balloons come in. Knowledge of the stratosphere, the home of the ozone, is at this point primitive, and the experiments he is doing should shed light on how much ozone is still there and how it is affected by various chemicals.

"Everyone is waiting with bated breath. His information will be absolutely critical," says Myron Uman, executive secretary of the environmental studies board of the National Research Council. Anderson's findings are expected to provide crucial information for the government on a host of environmental questions, including limits on aerosol cans.

Anderson's basic research interest is to get an idea of what the stratosphere looks like, and what are the chemical reactions going on within--no simple task. Predicting the stratospheric gas mixtures is comparable to predicting the chemical composition of water somewhere in the midst of an ocean, a job that can not be done from the ground. So Anderson must bring his lab to the stratosphere.

Years ago, Anderson would send his balloons about 140,000 feet up and then drop packages of measuring instruments by parachute, allowing them to take readings of the chemical composition in the air as they hurtled back to earth. Anderson says that although the experiments yielded useful information, the results were prone to error and difficult to test for accuracy since each experiment was a one-shot deal.

To remedy the problem, Anderson devised the "reel-up, reel-down" technique, whereby his instruments are hung over the side of the balloon and reeled up and down through the stratosphere as needed. The device not only allows his experiments to be repeated, says Anderson, but it permits numerous readings at various altitudes.

The gigantic yo-yo consists of a platform weighing more than a ton and hanging under the side of the balloon, an eight-mile cable and a 130-pound "monkey."

The monkey contains the instruments and goes up and down in the stratosphere; it consists of three elongated hollow "doughnuts" which fire a beam of light through its center hole as stratospheric gasses pass through. The light absorbs oxygen and measures the concentration of atmospheric gasses.

While Anderson has some suspicions about the extent of the danger to the ozone, he is treading very carefully, mindful of the enormous caution with which the government is approaching the issue. Clamping down on the production of certain types of gasses in, for instance, the aerosol industry could draw a backlash from businessmen.

"Our understanding is still primitive. We know the process is significantly altering the composition of the stratosphere, but nothing should be passed until we get more scientific information," says Anderson, who has testified before Congressional committees on the matter.

He adds, "We're at the stage where we have to build evidence like a lawyer in court. We can't talk about free radicals and tell people to shut down their plants until we can show a definite cause-and-effect relationship. We must show we understand what we're talking about." Legislation limiting certain kinds of chemical emissions simply is not warranted now, because researchers do not yet know enough about their effect on the ozone layer, he and other scientists say.

"It may seem to be fence-sitting, but we can't really make an honest evaluation yet," says Baird Professor of Science Dudley R. Herschbach. "There appears to be a long-term danger, but we still can't tell the extent of it."

Scientists, though, are irritated by a series of recent government reports down-playing the dangers to the ozone. One study has it that fluorocarbons will reduce the ozone content by only two to four percent by the end of the century; previous estimates put the figure at as high as 16 percent.

Experts fear that such conclusions will reduce the impetus to finding a solution to the problem. This in turn, they say, could further excerbate the current trend to less funding for atmospheric research, which would be disastrous to long-term efforts in the area.

Anderson says that research done by him and Michael B. McElroy, Rotch Professor of Atmospheric Science, indicates that the "fluorocarbon situation is much worse than we believed it to be few months ago. We think we have only five to 10 years to establish our case." And so it is back to the balloons.