UNITED STATES ARMY
CHEMICAL CORPS BIOLOGICAL LABORATORIES

FORT DETRICK, MARYLAND

CMIR D-BL-10-PD 7 October 1960

Dr. Joshua Lederberg
Medical Center
Stanford University
Palo Alto, California

Dear Joshua:

Inclosed, as requested, is an additional copy of the statement given
to the National Academy of Sciences. This merely stated that outside air
seldom contained more than one bacterium per liter, and gave no supporting
data. Another publication of ours on sampling methods, which I am also
inclosing, contains more information (page 17). These are the main data
on which the NAS statement was based and were collected by the same group
from USPHS who co-authored the sampling monograph with us. The Detroit
tests extended over a full year and this is only a brief summary of those
data, but the summary is typical of all the data collected. The Oatland
Islend, Savannah, Georgia, data were obtained by the same group in their
own back yard.

You are certainly right about the little information you can find
on this subject. The USPHS studies were never reported in the open
literature, except in this sampling monograph. We have the information
in complete raw form since we coughed up with the money to finance” the
tests. So many of the few general studies that have been published were
done in unusual rather than usual locations, such as very high altitudes
or over the Artic. As a matter of fact, it wasn't until about twenty
years ago that we had adequate equipment to make such determinations in
a quantitative manner. Almost all the work earlier done on this was
merely based on fallout on open petri dishes, and there is almost no way
to translate such counts to atmospheric concentrations. Cur main reason
for publishing the monograph with the PHS was because so few people still
seem to know how to sample bacterial aerosols.

I did ask Frank Wagner down the hall to jot down the references to
articles which he had tucked away in his desk and I am inclosing his list.
It makes no aim at completeness, and some of the articles, I fear, are on
techniques only and give no data. This may stir him up into working up
a decent survey of the aerosol data, and if so I'll see that you get a
copys The first article on his list is quite good. I had not read it

 
CMIRD-BL-10-PD 7 October 1960
Dr. Joshua Lederberg

until your letter set me inquiring, and it contains references to other:
pieces of work which are not on Frank's list and which I have not seen.
Interestinsly enough, the Moscow data seem to agree very well with the
data we bribed the PHS to collect in Detroit.

I know of no instances where bacterial counts and total aerosol
solids were determined simultaneously and I woyld hesitate to hazard a
guess as to what the ratio would be. About 10° bacteria per gram is
not too bad a figure for dry Kansas dirt, I suppose, and this might not
be too bad a figure for the aerosol ratio. However, I would expect the
aerosol ratio to be higher in so-called clean country air where the main
loading factor was soil or dust, than in industrial city surroundings
where artificial circumstances cculd increase the solids in the air without
contributing much to viable bacterial counts. Kansas dust, again rather
than Detroit filth, should account for most of the air microflora, I
would expect. If this guess is true, old dusty Mars might have more
numerous flora than Farth.

Sincerely,

Chale

CHARL™S 8. PHILLIPS
Chief, Physical Defense Division CTL

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