I have to disagree in part with Milton Leitenberg [Free for All, Aug. 14]. In his discussion of biological terrorism, he specifically cites the efforts of the Japanese group Aum Shinrikyo, saying it "had made a substantial effort to produce biological weapons as well" as chemical weapons.

He makes the same mistake as many do when they discuss biological warfare, confusing weapons and agents. Agents are the pathogenic substances that cause illness; weapons are the delivery vehicles by which the substances are disseminated. Leitenberg claims the Japanese group, with all its advantages, was unable to produce agents. Such production is fairly easy. Few question the group's ability to produce biological agents. The problem was devising a weapon that would disseminate the agent in a mode that would produce casualties.

Many years ago, I took part in a study that included determining the feasibility of developing an effective delivery system. The conclusion was that two factors made it difficult, if not impossible.

The first factor: the capability to attain a particle size (1 to 5 microns) that will easily be inhaled and retained in a quantity to cause infection. The quantity estimated for anthrax is 8,000 to 10,000 organisms. This is not simple to do.

The second major factor is the microweather condition, which involves, to use a popular phrase, which way the wind is blowing in the region about six feet above surface level. Wind conditions vary greatly and are influenced by variations in the ground surface and temperature and other obstacles -- vehicles, people, poles, trees. Wind speed will affect how fast the agent will sweep by the target and thus the exposure. To this must be added the air content -- moisture and particulate matter to which the agent could adhere.

To conclude, it appears for now that the terror from biological weapons has to do with the threat of their possible use, not with their ability to cause mass infections.

-- J. E. Dolan