The trains that rumble from the Harlem River rail yard in the South Bronx are sealed tight, but there is no mistaking what lies inside them.

The stench gives it away. The trains, some a mile long, are filled with garbage.

The railcars are part of an armada that performs a nearly constant exodus of waste from the nation's largest city. Each day, trains and trucks carry 50,000 tons of trash from New York to huge landfills and incinerators in New Jersey, Ohio, Pennsylvania, Virginia and South Carolina.

Waste management experts say these types of long hauls have become the norm for big cities as landfills fill up and close. In 2003, nearly a quarter of all municipal trash in the United States crossed state lines for disposal, according to the Congressional Research Service. Ten states imported at least 1 million tons of trash that year, up from only two states in 2001.

In New York, Mayor Michael R. Bloomberg is now pushing a proposal to extend his city's trash hauls even farther, putting garbage on barges that could be shipped up and down the East Coast. The plan is probably still years away from fruition, but it is already fueling a fresh round of debate in places that could be potential destinations.

At issue for many importing states is the smell and the threat to the environment if the garbage is handled improperly -- reasons that more urban trash is winding up in rural communities where political resistance is likely to be minimal.

For instance, New York transports more than 1,300 tons of garbage each day to Fox Township, Pa., in hilly hunting country 130 miles northeast of Pittsburgh.

Michael Keller, a township supervisor, said living near the landfill is not that bad because it is hard to smell or see it from the street. But he cannot shake the worries that the landfill's protective liners might not hold up forever.

"My concern is that 50, 60 or 70 years from now, they'll be saying, 'What were those guys thinking, allowing something like this to be built in this community?' " he said.

New York's new disposal plan is also being closely watched in Virginia, which imported 7.8 million tons of garbage last year, up 67 percent from 1997, according to state figures. The issue has been contentious since the laws passed by legislators in the late 1990s seeking to slow the importation of trash were struck down by the courts.

"It's easy to get Virginians to say, 'We don't want Yankee trash,' " said Michael Town, director of the Virginia chapter of the Sierra Club.

But officials in the Portsmouth, Va., area are considering a proposal by a company called American Ref-Fuel to build a port that could receive up to 2,500 tons of waste a day from New York. A fee of between $1 and $1.25 would be paid for every ton brought in, generating $1 million per year, plus as much as $7 million more if enough of the garbage went to an existing incinerator.

"The way we figure it, waste is coming here anyway," said John Hadfield, executive director of the Southeastern Public Service Authority. "Maybe we can make a silk purse out of this sow's ear."

A similar flow of cash has certainly helped places such as Fox Township.

"We're rich," Keller said, noting the township has bought new police cars and firetrucks with trash tipping fees. "We have less than 4,000 people living here, and we have millions of dollars in the bank."

Despite the concerns of environmentalists, the risks for these communities are few, said Mickey Flood, chief executive and founder of IESI Corp., a Fort Worth company that owns landfills throughout the eastern part of the country.

Standard landfills do not accept hazardous materials, although keeping every hypodermic needle or can of oil out continues to be a challenge. Waste is also transported in sealed containers that are designed to be leakproof. All water that touches garbage is required to be treated for pollutants, Flood said.

"Landfills in the United States are not environmental issues," he said. "They are strictly political."

Still, problems occasionally arise.

In December 2003, two schools near a landfill in northeastern Pennsylvania temporarily shut down when an overwhelming stink made it impossible for students to concentrate in class. Investigators blamed the stench on decaying gypsum board and made adjustments to a system that extracts vapors from the trash and burns them off.

"Transporting all of this garbage so far away means that the people that generate it don't have to deal with its consequences," Town said. "And if that's the case, where is their incentive to create less of it?"

Bags of trash pile up in Brooklyn's Prospect Park. Much of New York City's garbage is sent to New Jersey, Ohio, Pennsylvania, Virginia and South Carolina.A truck leaves a waste management facility in Brooklyn. Each day, New York City sends out 50,000 tons of trash. The trash next to a baseball field in Prospect Park, Brooklyn, is likely to be exported to another state.