New information about the risk of storing 1,500 tons of mustard agent at Aberdeen Proving Ground -- and demands for safer storage -- is raising questions about the Army's rationale for building a huge incinerator there.

For years, the Pentagon has insisted that the stockpile is dangerous to store or move and should be burned as quickly as possible.

But the Army may be its own worst enemy, critics say, and it can take action to lessen the storage risk.

A recent National Research Council study prepared for the Army said that, among the eight U.S. chemical weapons depots, Aberdeen's stockpile poses the highest risk of a serious accident during storage because it is kept outdoors near an airfield, and because it is near a densely populated area.

Some Aberdeen officials said they question the accuracy of the council's statement.

The airstrip, Weide Army Air field, is used extensively by the Maryland National Guard. It is one mile from the stockpile.

Recently, members of a state advisory panel and others suggested that closing the airfield or moving the stockpile would significantly reduce the storage risk and allow more study of alternatives to incinerating the mustard agent.

The suggestion to close the airstrip struck a nerve.

The Army and the Guard immediately responded that Weide is vital to the Guard's mission.

But the 140-acre airfield has another, little-known purpose: The Army uses it to ship small quantities of dangerous and deadly chemical warfare agents to private laboratories and military installations throughout the country.

Contractors use the chemicals to test protective clothing, antidotes and other gear. Military installations use them to calibrate air-monitoring and analytical equipment.

"Certainly, the airfield is important to the [Army] missions and to the National Guard," said Gary Holloway, a proving ground spokesman.

The chemical shipments from Weide support the Army's continuing research into chemical warfare defense.

The proving ground's Edgewood area, formerly known as Edgewood Arsenal, is the U.S. military's leading research center for chemical warfare defense. There, at Building 3832, also known as the Chemical Transfer Facility, the Army maintains quantities of nerve agents, blister agents and other chemicals that might be used against U.S. troops.

Small amounts -- the Army says they're always less than a liter -- from the facility are put in heavy, sealed containers for air shipment from Weide, Army officials said.

In response to written questions from The Sun, the Army said it made 34 such shipments during fiscal year 1993, involving five types of nerve agents, and mustard agent and lewisite, two blister chemicals.

In addition, an average of five such chemical shipments arrive at Weide each year from military installations and contractors, the Army said.

But members of the state advisory panel and others say that if the airfield is too important to close, even temporarily, the Army should consider moving the stockpile farther away or enclosing it in a sturdy building or underground structure.

At Aberdeen, the Army is most concerned about a small plane or helicopter crashing into the stockpile, and creating a large fire and a toxic cloud that could drift into heavily populated communities nearby.

Under worst-case conditions, the Army says, such an accident could cause more than 2,000 deaths.

Although the Army says the chance of a worst-case accident at (( Aberdeen is 100 million to 1, it may be more than just an abstract possibility.

Marilyn Tischbin, a spokeswoman for the Army's Chemical Materiel Destruction Agency, said a small plane made an emergency landing in an Army mustard-agent storage yard in Pueblo, Colo., in 1987.

The Pueblo stockpile is near a municipal airport, and it is believed to be safer than the Aberdeen stock pile because the munitions are kept in concrete bunkers, called igloos.

"They managed to land the plane safely between the igloos," Ms. Tischbin said of the incident.

The 50-year-old mustard agent stockpile at Aberdeen is scheduled for destruction in eight years as part of a national program to dispose of the military's 30,000 tons of obsolete chemical agents and chemical-filled munitions.

The Army is set to begin incinerating a 12,000-ton stockpile in Utah early next year, at a cost of about $1 billion. The current schedule calls for construction of a $489 million incinerator at Aberdeen to start in 1998 and burning to begin in 2001.

Army officials insist that incineration is safe and efficient, and say that prompt burning is necessary because of growing storage risks and pressure for global chemical disarmament.

Opponents of incineration say the service should take more time to develop a safer disposal method.

After pressure from residents near the stockpiles, environmental groups and Congress, the Army recently agreed to spend as much as $200 million studying alternatives to incineration, namely chemical and biological methods of detoxifying the material.

At Aberdeen, discussion of the airfield -- and its proximity to the mustard agent stockpile -- has brought the disposal debate to a head.

"They are in a box," said John Nunn of Kent County, who chairs the nine-member Maryland Chemical Demilitarization Citizens' Advisory Commission. "They created the circumstance that makes this so dangerous."

Sen. Paul S. Sarbanes, D-Md., also has asked Army Secretary Togo D. West Jr. for an "immediate" review of the issue.

The Kent County commissioners, in a recent letter to the Army, said the airfield issue calls into question an extensive, multimillion-dollar emergency planning effort that is focusing on jTC

the risk of an aircraft crash at the mustard agent stockpile.

"It would be inefficient and misleading to continue the emergency planning efforts . . . when the risk being planned against could be minimized or eliminated," the commissioners wrote.

Nearly 300,000 people live within 15 miles of the Aberdeen stockpile -- the largest population bordering any U.S. storage site for chemical weapons. The emergency planning effort involves residents in Baltimore, Cecil, Harford and Kent counties.

Kent County pulled out of the emergency program once, arguing that it was being used to justify incineration.