McDonald's Corp.'s decision to switch from polystyrene containers to paper for its food products is being hailed by some - but not all - environmentalists.

"It is a mistake to make plastic the great satan and paper the great saint," said Jan Beyea, a scientist at the National Audubon Society. "Both processes generate pollution."A recycling company, meanwhile, lamented McDonald's announcement that it would start phasing out its clamshell-shaped containers - which had been blamed for filling landfills and depleting the ozone layer - within two months.

The fast-food giant had been playing a key role in educating the public about the need to recycle, said E. James Schneiders, president of National Polystyrene Recycling Co.

McDonald's just last week said it planned to expand an experimental plastic recycling program to all of its 8,500 U.S. restaurants.

"NPRC is disappointed to learn that McDonald's has decided to phase out its use of polystyrene foam packaging," Schneiders said.

But the non-profit Environmental Defense Fund, which had worked with McDonald's since August on plans to phase out the plastic foam containers, was elated.

"McDonald's understands that the future is green," said Frederic D. Krupp, the fund's executive director. "I think other companies will follow suit."

Several U.S. cities have banned the use of polystyrene foam, saying it contributes to landfill problems by lingering for years before disintegrating. The polystyrene production process also is suspected of harming the Earth's ozone level.

"Although some scientific studies indicate that foam packaging is environmentally sound, our customers just don't feel good about it," McDonald's President Edward Rensi said Thursday from the company's suburban Oak Brook headquarters. "So we're changing."

Joseph Bow, president of the Foodservice & Packaging Institute in Washington, accused McDonald's of "bowing to public pressure that is based on misconceptions and misinformation."

"You don't want to get rid of them (polystyrene products) all together," he said. "They provide consumers with a sanitary and timesaving method of food delivery."

A spokeswoman for the Environmental Protection Agency in Washington, Robin Woods, said her agency had no studies that indicated foam packaging is environmentally sound. But she also said, "It may not be an environmental hazard because it's inert. It's not something that breaks down easily and leeches into landfills, for example."

McDonald's said the foam containers will be replaced by paper products manufactured in a new process that will preserve the food's temperature and freshness.

McDonald's Vice President Shelby Yastrow said the polystyrene containers are made for McDonald's by several companies, including Amoco Foam Products Co., Mobil Corp., Jen-Pak and Huntsman Chemical.