BERKELEY, CALIF. -- The environmental watchdogs of this socially conscious city, accustomed to taking on such giants as the nuclear power industry, have focused their energies on a new foe: Ronald McDonald.

Envisioning an Earth choked with trash and soaked in ultraviolet rays, the Berkeley city council wants to remove -- fast and for good -- the styrofoam containers made with chlorofluorocarbons that keep the McDLT's hot side hot and cold side cold, and any other fast foods wrapped and insulated in containers made from CFCs, as the chemicals are called. The manufacture of CFCs, it has been found, depletes the ozone layer of Earth's upper atmosphere that protects the planet from damaging ultraviolet rays.

Passage of the proposal would preempt a McDonald's Corp. decision to switch by the end of the year to foam packaging made from chemicals other than CFCs, a process under way. But the council also is considering a ban on all fast-food foam packaging, whether made with CFCs or not, by January 1990.

Joseph Bow, spokesman for the Foodservice Packaging Institute, a trade association, said manufacturers have been concerned about CFCs and plan changes. But he contended that the industry accounts for less than one percent of overall CFC use. "The amount of CFCs we release is basically insignificant," he said.

Berkeley, Bow said, "likes to be the center of the environmental universe . . . . If somebody wants {the transition from styrofoam containers} in 18 months, they want it in two months to show everybody they are environmentally aware, and it gets their name in the paper."

Council member Nancy Skinner agrees that banning CFCs in fast-food containers "may be an insignificant drop in the bucket as far as stopping the ozone depletion. But if it causes the country, the manufacturers and the lawmakers to look for alternatives, then it is significant."

McDonald's decision to discontinue CFC containers and the fear of legislation similar to Berkeley's have sparked most manufacturers of foam products to switch to other chemicals.

The Food and Drug Administration recently approved a chemical manufactured by Du Pont that will replace some of the CFCs in food-service packaging. Other manufacturers have switched to pentane and other non-ozone-depleting chemicals. The packages made with the alternative chemicals look the same as those made with CFCs.

"Within a period of 12 months, there will be few if any of the CFCs used in the manufacturing of foam products," Bow said.

McDonald's, the world's largest fast-food chain with more than 9,900 outlets worldwide, is committed to foam containers because they provide the best service for the customer, a spokesman said.

"We asked our suppliers to begin a prompt phase-out of the use of CFC in our packaging {containers}," said the spokesman, Lana Ehrsam. "Thousands and thousands of stores already are converted. If the store {in Berkeley} has not made the changeover, we will bus the new containers in and respect the law."

Chlorofluorocarbons are commonly used in air conditioning and refrigeration systems, in foam products and, outside the United States, as aerosol propellants. In 1978, the U.S. Environmental Protection Agency banned CFCs in aerosols after scientists warned that the chemicals were destroying the ozone layer.

The proposed ban in Berkeley is self-regulating and assesses no penalities for violations. Since 1982, when the city's landfill pit closed because it could hold no more waste, the city has searched for ways to reduce and recycle garbage, and its Solid Waste Management Commission has asked fast-food restaurants voluntarily to reduce nonbiodegradable packaging by 50 percent.

Roger Bernstein, director of state government affairs with the Society of Plastics, said that fast-food foam products account for only 0.14 percent of municipal solid waste. That foam containers are not biodegradable is a virtue because "when paper products decompose they create methane gas and contaminate the underground water supply," he said.

The EPA says all landfills -- with or without foam products -- will create methane gas.

Most of Berkeley's 400 fast-food restaurant owners say they would comply with a CFC ban because of the chemical's harmful effects and the availability of alternative foam products. Jack-in-the-Box uses such foam containers, and Burger King uses biodegradable containers. But most owners say eliminating all foam containers would hurt business.

"This {proposed ban} would be a great hardship on all the businesses here, especially the small ones," said Frank Kalmer of Lox Stock and Bagels. "There are some uses for foam that cannot be substituted. I serve coffee at 140 degrees and soup at 160 degrees and the customers would burn their hands with paper containers. They aren't as sturdy, either."

But at Sufficient Grounds, a coffee shop where students and faculty from the nearby university meet over hot cups of espresso and cappuccino, the CFC issue prompted the use of paper cups several years ago.

"Coffee tastes just as good if not better in paper," said Carol Damon, a shop customer. "You have to know how to hold it, but there's something very wholesome about drinking out of a paper cup," she said while holding a paper cup of coffee with her thumb on the rim and her fingers on the bottom.

Several store owners, however, said that paper packaging costs more than foam products. A public hearing on the ban is scheduled later this month.