Drink some cool milk for breakfast, drive to work with the air conditioner blasting, type away at your computer and then take a quick break for a hamburger at the local fast-food outlet. Come home and take a nap on the soft-cushioned couch. Chances are you didn't know it, but each of these pastimesinvolves the use of a class of chemicals that are endangering the health of our planet.

Chlorofluorocarbons, or CFCs, have carved out a pivotal niche in modern life. As coolants in refrigerators and air conditioning systems, as cleaning fluids for the electronics industry, as insulating materials in packaging, as rigid and flexible foam for cushions and home insulation, CFCs have become an increasingly large part of our everyday life.

But industry now is trying to shift this dependence to other substances because CFCs are escaping into the upper atmosphere - the stratosphere - and eating away the ozone layer. And ozone is essential to protect the Earth from the sun's damaging ultraviolet rays.

The shift is bringing with it an unprecedented, wide-ranging search for alternatives to CFCs.

CFCs were used as propellants in aerosol cans until 1978, when they were banned in the United States. At that time, scientists were just beginning to realize that the chemicals were destroying the ozone.

By eliminating propellants alone, it was easy to make a large dent in CFC consumption because propellants encompassed 50 percent of the market. However, once aerosols were removed, a host of other CFC applications emerged. Now 10 years later, CFCs are being produced at levels exceeding the pre-1978 ban.

While CFC production has increased, the evidence incriminating the chemicals also has grown. In September 1987, several nations drew up an agreement limiting the use of CFCs. The agreement states that by 1993, participants must make a 20 percent cut in production and a 50 percent reduction by 1998. To date, 46 countries have signed the document, known as the Montreal Protocol.

At an international conference in London this month, 12 members of the European Economic Community voted to reduce CFC production by 85 percent and to seek a total ban by the year 2000.

The Montreal Protocol sparked a flurry of industry activity. E.I. du Pont de Nemours and Co., one of the largest CFC producers, announced it would begin phasing out its production. The food-packaging industry said it would abandon CFCs, which are presently used in containers for fast food, eggs, meat, etc.

To meet the protocol deadlines, scientists are racing to develop alternatives. An international group of 14 manufacturers of CFCs joined to carry out toxicity testing on leading candidates. They hope to speed the regular process by working together and make the new products available by the mid-1990s.

"We're all optimistic that these products are coming along very quickly," Stephen Andersen of the Environmental Protection Agency said. However, there is a general consensus among industry representatives that no single product will replace CFCs. "We feel that it's going to require more than one material to replace all of our . . . needs," commented John Fisher of AT&T Bell Labs in Princeton, N.J.

Several alternative compounds are similar to existing CFCs with slight modifications to the chemical structure. By adding a hydrogen atom, for example, the compound becomes less stable and therefore breaks down before it reaches the stratosphere where it would otherwise do harm.

Du Pont already has begun marketing one alternative for the food-packaging industry. By adding hydrogen, the compound, Formacel (HCFC 22), has 95 percent less ozone-depleting potential than CFC 12, the substance it replaces. The Food Service Packaging Institute has just switched to the substitute.

Also on the horizon is a replacement for refrigeration and cooling systems. The most promising substance, HFC 134a, is still undergoing toxicity testing, which will require approximately five years to complete.

Since 134a and most of the other alternatives operate at different temperatures and pressures than their original counterpart, equipment must be modified to accommodate them. However, as long as the equipment is functioning, it retains the coolants sealed within the system. Only when a unit has lived out its life span and begins to break down do the CFCs leak and escape into the atmosphere.

At that point, large commercial refrigerators, freezers and office air conditioners can be retrofitted to accommodate the alternative compounds, according to Kathleen Forte, senior pubic affairs specialist at Du Pont in Wilmington, Del. For small items such as home refrigerators, it makes more sense economically to replace them.

Prices for the new refrigerators equipped with non-CFCs shouldn't be much higher, Forte said. An average home-size unit needs only six ounces of refrigerant, which today costs less than a dollar. Though Du Pont projects the CFC substitute, 134a, will cost two to five times more, it will barely affect the final price of the refrigerator.

However, the cost increase will be much more obvious for commercial applications. An office air conditioner installed in a 150,000-square-foot building requires 1,500 pounds of coolant. A doubling or greater on that cost will raise the price of the system considerably.

The expense associated with new equipment applies also to the electronics industry. New compounds developed for cleaning electronic parts and circuit boards require special machinery for dispensing the cleaning agent. Existing machines can't accommodate the new products.

One of those new compounds, which AT&T has been using since 1986, was developed by Petroferm, a small company in Fernandina Beach, Fla. BIOACT EC-7 is based on a completely different approach than other substitutes. The chemical, derived from citrus rinds and coniferous trees, bears no resemblance in its chemical structure to CFCs.

Fisher from AT&T said they hope to eventually use BIOACT EC-7 for 20 percent to 30 percent of their needs, although it has certain limitations. The components must be rinsed with water and not all parts can be immersed in water.

IBM also is experimenting with a new method of cleaning small computer parts. "It's not a revolutionary new alternative," said Ray Kerby, director of environmental programs at IBM in San Jose, Calif. They simply use a mixture of water and a soapy substance along with ultrasonic vibration. "What we've done is spend the last couple of years on technical work, sharpening up its applicability to our particular cleaning," Kerby said. They are working with mechanical parts that must be spotless to function properly. "Even a fingerprint can be a mess," Kerby said. "Absolute cleanliness is super-important."

The technique won't work on circuit boards or semiconductors or anything containing solder flux, the residue from soldering. But, according to AT&T's Fisher, searching for cleaning replacements may be the wrong approach.

"There are other alternative paths to take. In many cases, I think the American industry cleans circuit boards and other things that don't necessarily need to be cleaned. Very often, we could be using fluxes for soldering that don't necessarily have to be removed from the board after soldering."

David Wirth, senior attorney at the Natural Resources Defense Counsel, also advocates cutting non-essential uses. "The non-essential uses should be the first ones to go," Wirth said. "There are still a large number of them out there." This includes egg cartons and fast-food packages, which could be replaced by other substances, such as cardboard.

In addition to cutting non-essential uses, other avenues exist for bypassing the introduction of new chemicals. CFCs are extremely volatile. By containing them in a closed unit or under a hood while cleaning electronic parts, their lifetime can be extended. In the past, CFCs have been routinely vented to the atmosphere when recharging auto air conditioners. Producers are now encouraging users to contain the compounds during this process. In addition, the chemicals can be recycled rather than disposed of after each use.

Representatives from industry, regulatory agencies and public interest groups all voiced optimism that the deadlines outlined by the Montreal Protocol can be met. But Fisher expressed a word of caution about focusing too heavily on specific deadlines and guidelines.

"I don't think we should be shooting for a 50 percent reduction by 1998. I think we should really be trying to eliminate CFC usage altogether. Anyone shooting for just a 50 percent reduction is missing the boat. I think we ought to be trying to eliminate CFCs . . . wherever we can."