Theresa Byrne, who lives in Salem, Ore., said the city took too long to inform residents that most plastics and egg and milk cartons were now considered garbage. “I was angry,” she said. “I believe in recycling.”

Other communities, like Grants Pass, Ore., home to about 37,000 people, are continuing to encourage their residents to recycle as usual, but the materials are winding up in landfills anyway. Local waste managers said they were concerned that if they told residents to stop recycling, it could be hard to get them to start again.

It is “difficult with the public to turn the spigot on and off,” said Brian Fuller, a waste manager with the Oregon Department of Environmental Quality.

The fallout has spread beyond the West Coast. Ben Harvey, the president of E.L. Harvey & Sons, a recycling company based in Westborough, Mass. , said that he had around 6,000 tons of paper and cardboard piling up, when he would normally have a couple hundred tons stockpiled. The bales are filling almost half of his 80,000-square-foot facility.

“It’s really impacted our day-to-day operations,” Mr. Harvey said. “It’s stifling me.”

Recyclers in Canada, Australia, Britain, Germany and other parts of Europe have also scrambled to find alternatives.

Still, across much of the United States, including most major cities, recycling is continuing as usual. Countries like India, Vietnam and Indonesia are importing more of the materials that are not processed domestically. And some waste companies have responded to China’s ban by stockpiling material while looking for new processors, or hoping that China reconsiders its policy.