Part III - Historical Survey of the Porton Down Service Volunteer ...

9.3 Human studies of the penetration of liquid GB
No human studies involving Service volunteers having liquid GB placed on their skin (or on
clothing on their skin) were carried out between 1954 and 1989. However, much effort was
devoted to understanding better skin and clothing penetration. Excised or resected human
skin was used in studies in 1954 [21, 22] with radioactively-labelled GB. Human skin
samples from the back, forehead and hand were used in the first half of 1960 to measure the
rate of penetration of liquid GF [23].
The part played by skin fat was studied in animals in 1956 and 1957 [24]. This work
continued with excised human and animal skin in 1960 [25]. The results prompted volunteers
to contribute to studies of skin penetrability, as described below:
• One of the conclusions of the work in 1960 was that dead skin cells (called
keratin) seemed to be a barrier to the penetration into the skin of liquid GB.
However, it was not known how much keratin was normally present on human
skin.
• A method was found in 1960 to measure the weight of keratin stripped from
human skin [23] and a mathematical model was produced which related the
penetration rate of GB to the amount of keratin and the electrical conductivity of
the skin.
• As a consequence, during 1960 and 1961, Service volunteers had keratin
stripped from their skin [26] so it could be weighed. Typically, the keratin was
removed by placing a piece of adhesive tape on the skin and then peeling off the
tape to remove dead skin cells. Sometimes "massive keratin-stripping" was
carried out. Here, the forearm was often used. A site was shaved, and then
pieces of adhesive tape were applied and removed from the same site several
times. Keratin was removed also from the shoulder blade region of the back [27].
Seven women volunteers from the Porton staff contributed keratin in this manner
[27] and it was found that the amount removed from them differed only slightly
from the amount of keratin stripped from men.
• In 1961 [26], after keratin had been stripped by adhesive tape from parts of the
skin of human volunteers, the electrical conductivity of the keratin-stripped skin
was measured. Typically, that was carried out by placing electrodes on the skin.
This contribution of Service volunteers in skin penetration work did not involve their being
exposed to nerve agents. Volunteers took part in further studies of skin penetration, none of
which involved nerve agents:
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• In 1960/61 [28] volunteers took part in studies with radioactively-labelled tri-npropyl
phosphate (TPP). TPP was at that time a simulant for GF, that is to say it
had the physical properties of GD but did not induce the effects of it. Typically, a
volunteer would have a small drop of one of these liquids placed on the bare skin
of the forearm. The drop was covered and the penetration into the skin
measured by a Geiger counter. Work was conducted on normal skin and on a
patch of skin from which keratin had been stripped [28].
• From the work with keratin and by measuring the electrical conductivity of skin,
Porton built up a picture of how liquid penetrated the skin. It became apparent
that penetration might depend on the electrical charge of ions in the liquid placed
on the skin. In 1961/62 [29] volunteers took part in studies of the penetration of
sodium, potassium, phosphate and bromide ions through the skin. No report
specifically on this work has been found but it appears that drops of water
containing these ions were placed on the arms of volunteers [29]. This type of
study was conducted periodically up to June 1965 [30]. The electrical charge of
the ions was not found to influence the penetration rate [29].