JOSHUA LEDERBERG

1230 YORK AVENUE - NEW YORK, NEW YORK 10021-6399
(212) - 327-7809

November 18, 1992

To: David Gakenheimer:
Subject: Comments on TMD Blue Ribbon Review Report

I have read the summary with great interest and concur in every detail on which I can claim
expert knowledge. In particular, I would strongly endorse NOT using live pathogens in field
oriented trials. This will not only attract very difficult political attention; it will also greatly
complicate the execution of the tests. Of course relevant parameters, comparing anthrax with
other spore-formers in response to heat, radiation, etc., should and can be carefully measured
in small laboratory scale experiments.

There are some underlying assumptions about decay of biological agents in the atmosphere
(apart from kill mechanisms by the interceptor) that are not well understood. For example,
the estimated LD-50 for anthrax has been estimated at about 10,000 spores. This is
sometimes misread as an abrupt threshold, that there is zero likelihood of infection with, say,
1 spore. If, as is more likely, the biological response is probabilistically proportional to the
dose, then 1 spore will have a likelihood of infection ~10*-4, a small cross-section, but one
that can not be ignored for large populated targets. That is to say, in contrast to chemicals,

mere dispersion and dilution is no comfort: it may however allow more time for active kill
mechanisms to take hold.

In that regard, we must also consider scenarios in which attacks are made at night or in heavy
overcast; and also the microencapsulation of biological agents to afford them UV-protection.

These perspectives are consistent with the report, but perhaps might be highlighted.