WASHINGTON - Fifteen years after recycling entered the use-and-toss consciousness of the average American consumer, the record of participation has been pretty good. Today, more than 30 percent of the nation's waste is recycled, up from about 10 percent in 1987.

But complacency and economics are combining to threaten progress in reusing what we would otherwise throw away. For the first time in many years, the number of aluminum cans tossed into the trash last year exceeded the number separated and carted off for recycling. The recycling of paper and plastic never reached the 50 percent-plus levels that aluminum did, and they remain behind by 10 to 20 percentage points.

"To some extent, recycling is being undone by its very success," said Allen Hershkowitz, a scientist with the Natural Resources Defense Council.

"Success" is relative, of course. When recycling first hit the mainstream, the nation seemed to be facing a garbage crisis. Not only were the alley trash cans filled to overflowing, but so, too, were the nation's landfills. Television cameras rolled as a barge loaded with trash from Long Island, N.Y., sailed down the East Coast, turned away at every port as it looked for a place to dump its cargo.

The situation has improved dramatically since then, as many Americans changed their habits and set up separate containers for their recyclable wastes. By 1998, there were 9,000 curbside pickup programs and 12,000 drop-off centers nationwide, according to the Environmental Protection Agency. Safer landfills have been built, including "megafields" in Virginia, Pennsylvania and other states that take out-of-state garbage as well as their local waste.

But now that recycling is mainstream -- no longer a hip, politically correct ethos -- its momentum is faltering. New York City, facing budget pressures, recently suspended its plastic-recycling program for a year and its glass-recycling program for two years. If you want to recycle in New York these days, you are limited to paper and aluminum. Denver and Dallas have also been battling over whether to reduce their recycling programs to help balance their budgets. It's not that a recycling program necessarily costs more than garbage collection, according the National Recycling Coalition, but garbage collection is mandated by law, while recycling often is not.

Even many of the cities that are still enforcing mandatory recycling at homes don't have programs or regulations governing recycling at office buildings, bars, restaurants, schools or stadiums. As a result, many of those cans go into the trash, said Kate Krebs, executive director of the National Recycling Coalition, whose membership includes state and local recycling coordinators as well as manufacturing and recycling companies. Some cities have regulations that require companies to have bins or containers for recycling, and others have economic incentives for companies to reduce the amount of trash they generate. But there isn't much enforcement of recycling away from home, she said.

The recent economic boom may be another factor in the decline in aluminum recycling. Given that the unemployment rate has been below5 percent for five years, can scavenging has declined, said several industry and environmental officials. There are fewer places to resell collected cans than there were a few years ago, according to Craig Covert, market development manager at Alcoa's Rigid Packaging division.

"In the 1990s, there used to be 10,000 places to sell your cans -- different scrap dealers and recycling centers," he said. "It might be half of that now."

Moreover, the value of each scavenged can has declined, given that most cans are lighter today than in the past. The price for a pound of used beverage cans has stayed within a 45-to-55-cent range since 1980 -- or relatively flat, according to a report by the Container Recycling Institute, a foundation-funded organization that promotes recycling. So inflation has eroded the gains to can sellers.

In the 10 states that require deposits on containers, the deposit is a nickel or less in all but one. That's the same rate that was set when Oregon became the first state to require a deposit in 1971, the recycling institute noted, when a nickel was worth considerably more than today. (Even though a nickel isn't much, recycling rates remain higher in the states that require a deposit. Aluminum-can recycling rates are highest in Michigan, which requires a 10-cent deposit.)

One other factor that may contribute to recycling becoming an afterthought is the design of garbage cans and recycling bins. Recycling companies speculate that when consumers run out of space in their little recycling bins, the rest of the recyclables go into their super-sized trash cans.

Through the design of the collection containers, "we're telling the consumer to throw away 78 gallons and recycle 16 gallons," said the Aluminum Association's Robin King.