§ The Countess of Marasked Her Majesty's Government:
Whether they are aware of the US Department of Agriculture research which indicates that Deet when mixed with pyridostigmine bromide became 10 times as toxic to cockroaches, and whether this phenomenon would apply to humans treated with both chemicals.
§ The Parliamentary Under-Secretary of State, Ministry of Defence (Lord Henley)Responsibility for this matter has been delegated to the Director General and Chief Executive of the Chemical and Biological Defence Establishment, who has been asked to arrange for a reply to be given.
Letter to the Countess of Mar from the Director General of the Chemical and Biological Defence Establishment, Dr. Graham Pearson.
1. Your Parliamentary question to Her Majesty's Government of 7 July 1994 asking whether they are aware of the US Department of Agriculture Research which indicates that DEET, when mixed with pyridostigmine bromide, becomes 10 times as toxic to cockroaches and whether this phenomenon would apply to humans treated with both chemicals has been passed to me to answer as Chief Executive of the Chemical and Biological Defence Establishment.
2. We are aware that a scientist working at a US Department of Agriculture Experimental Station has described an observation to the US Senate Veterans Affairs Committee in which he claims that DEET when used in combination with pyridostigmine became 10 times more toxic against cockroaches. We have not, however, seen any detail of the observation and therefore do not know how the reported observation was made and how the pyridostigmine was administered. I have consulted my colleagues in the United States Department of Defense, who have been unable to obtain any detail of the basis for the observation.
3. In considering this report, it is important to recognise that a cockroach is not a representative model for man, as insects have a totally different metabolism
50WA
Preparation Use on personnel Use on clothing Use on bedding Use on/in accommodation Insectides1 Nil use "Peripel" (permethrin)— Some desert issue combat clothing was impregnated with Peripel in acccordance with the manufacturers instructions Nil use "Ficam" (bendiocarb)— One tented camp in A1 Jubayl was sprayed with Ficam prior to arrival of troops from man. DEET is a commercially widely available insect repellant which is formulated as a lotion or cream for application to the skin. The oral toxicity of DEET to rats is very low, being about 2 grams per kilogram, which is a comparable toxicity to many common chemicals such as salt and acetic acid (vinegar), whose oral toxicity in the rat is about 35 grams per kilogram. Furthermore, DEET formulated for use as an insect repellent which applied as instructed to the skin involves a much smaller concentration and is therefore very much less toxic than if taken orally.
4. Consideration of the chemical formulae of DEET and of pyridostigmine bromide does not suggest that there would be any interaction. In addition, although pyridostigmine bromide is used in the treatment of patients suffering from rnyasthenia gravis involving very much higher doses than those taken by Service personnel in the Gulf conflict, we are unaware of any evidence to suggest that myasthenia gravis patients are harmed by the us of the insect repellent DEET.