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

Figure 8.1. Variation of ChE Inhibition induced by GB on bare skin [66]
Estimates of LD50 (clothed skin) for man were made in the same report. For GB, the
evidence of the main study suggested it "cannot be greater and may be less" than the bare
skin estimate. Liquid GD and GF had only been placed on the bare skin of man in the large
study but work had been conducted with liquid GD and GF on clothed animal skin. If the
clothing protected man in the same way as it protected animals, the LD50 (clothed skin) for
man could be estimated at 1200-1400 mg for GD and 1080 mg for GF [66].
8.5.5. A case of severe poisoning and a fatality
On the 27 th April 1953 one of the six men who received a 300mg dose of GB in the main
human study suffered severe poisoning [69]. The dose was administered in 30 drops of
10mg on a layer of serge fixed to the upper forearm. The man was subsequently
hospitalised, his breathing temporarily ceased and he suffered convulsions; but he recovered
some days later. The points observed from the incident in Porton reports published
afterwards [67, 69] were:
• Three of the 26 men who had received this dose on serge had shown "mild and
temporary systemic responses (nausea and vomiting)".
• The man's pre-exposure RBC ChE activity was 82 Warburg units. This was
described [69] as "low" and "may have been an important contributory factor" 4 .
4 Lower normal limits cited in earlier Porton reports [43, 70] for RBC ChE varied between 84 and 92
Warburg units; a value of 92 was cited in the report published in September 1953 [68].
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