Fears that terrorists may have planned to use crop-dusting aeroplanes to spray US cities with biological warfare agents need to be taken seriously, according to British experts. While such an attack would face technical difficulties, it could be extremely effective, they say.

"If you wanted to use biological weapons, one of the best ways is to use a crop duster," says Malcolm Dando, professor of international security at the University of Bradford. "It's not an unreal concern to have."

The spectre of a biological terrorist attack using crop-dusters arose on Sunday. Time magazine reported that the FBI had found a manual on crop-dusting among the belongings of one of the suspects for the World Trade Center attacks.

The FBI refused to confirm or deny the finding to New Scientist, but did order crop-dusters to be grounded on Monday. Crop-dusters were initially grounded on the 16 September, five days after the attacks on Washington DC and New York but the restriction was relaxed the next day in areas away from big cities.

The US National Agricultural Aviation Association website now carries a warning from the FBI urging members to report any suspicious interest in use of the planes. Crop-duster mechanics in Florida told CNN that a group of arab men had questioned them in August about the specifications of crop-dusters, including their carrying capacity.

Grab and grow

However, to carry out an effective attack, terrorists would first need to obtain and grow sufficient amounts of a virulent biological strain - most probably anthrax spores.

This is a significant task in itself, says Dando. Processing the spores so they distribute efficiently, get inhaled and remain in peoples' lungs long enough to cause an infection would also take expertise, he says.

Dando says the likelihood of such an attack is low, although the attack on the World Trade Center towers has changed how the risk of different attacks is assessed. "Before, the constraints on terrorism had a moral element, but that seems to have disappeared now," he says.

Night-time raid

The prospect of an anthrax attack was investigated in the 1990s by the US Office of Technological Assessment. They concluded that 100 kilograms of virulent anthrax effectively dispersed at night over Washington DC could cause between one and three million deaths. Crop-dusters can carry up to twice that capacity.

Dando says that the best way to reduce the threat is to prevent the proliferation of expertise in manufacturing chemical and biological weapons. This would involve an agreement among states to scrap their research programmes, he says.

"Once you get an agreement among most countries, you can focus your intelligence on those that don't sign up," he says.
 
SOURCE: NewScientist.com on the 24th September 2001