Citizens of rural Laytonsville in upper Montgomery County asked the county yesterday to shut down the Laytonsville landfill and provide them with emergency water, saying they feared their well water had been contaminated by medical waste from the National Institutes of Health that may have been dumped into the landfill.

The landfill sits atop a huge underground reservoir that provides well water for the almost 2,000 homes in the greater Laytonsville area. County officials discovered last month that NIH had improperly sent animal waste, bags of blood, blood-caked equipment and a dead research dog from its laboratories to the garbage transfer station at Gaithersburg, the last stop before the waste is taken to the Laytonsville landfill.

It is unknown whether any NIH medical waste made it all the way to Laytonsville before it was discovered. NIH safety director Emmett Barkley said he was convinced that no material shipped for Laytonsville was infectious. Federal law requires that infectious material be incinerated, Barkley said.

Barkley contends that noninfectious materials could be disposed of at the landfill. As for the dead dog, he said, "There was no excuse for that. We don't know how that got in there."

At a press conference yesterday Laytonsville Mayor Charles T. White and civic association president Harold O'Flaherty called on the county to shut down the 10-month-old landfill, until federal authorities could investigate how the NIH waste ended up at the transfer station and whether federal and state permit regulations have been violated. The civic association has also asked the U.S. Environmental Protection Agency to conduct an investigation.

Meanwhile, Rep. Beverly Byron (D-Md.), who represents the Laytonsville area, said she met with NIH officials last weekend and will be closely monitoring their efforts to prevent such improper dumping in the future.

County information officer Charles Maier said later that the county had no plans to shut the landfill or provide emergency water.

NIH safety officials initially convinced county workers that the problem was a mix-up and that the trash should have been incinerated at the NIH complex. But the problem recurred twice--one time with NIH waste showing up in bags clearly marked for "On-Site Incinceration" only--and county officials finally ordered the monitoring of all NIH deliveries to the transfer station.

"We're going to keep up this kind of intense surveillance," said Alan R. Bergsten, the county's solid waste management chief. "We're looking for anything with blood on it." He said state permit rules had not been violated, since county workers spotted the offensive materials in time.

NIH safety director Barkley said yesterday that the research facility has been so concerned with properly disposing of the most hazardous types of waste--radioactive and chemical--that pathologic waste disposal had not received as much attention.

Barkley said the discovery of the improper dumping has led to stricter controls, including new orders to housekeepers to inspect garbage cans, and new training classes for employes in patient care buildings.