Research is continuing into how they affect peripheral nerves and the brain. In Britain, the fears have increased because of the hundreds of farmers who appear to have suffered severe, long-term illness after using OP sheep-dip chemicals.
Dr Goran Jamal, a consultant at the Institute of Neurological Sciences in Glasgow, said: ``There's no dispute that there is a short-term effect on people exposed to OPs and an intermediate-term effect. First there are flu-like symptoms of lethargy and dizziness, followed by a weakening of the muscles around the hips and shoulders after three days."
Less is known about the more severe long-term effects,believed to result from repeated exposure. Dr Jamal said: ``There is evidence of physical damage to the nerves in the limbs.'' Furthermore, victims seem to suffer some memory loss, harm to their sense of balance, depression, fatigue and a change of personality which makes them prone to rages.
All the pesticides listed by the Government are licensed for use in Britain following toxicity testing on animals.
But they should only be used in strict accordance with safety rules, including the use of protective clothing, and there is evidence that both American and British troops failed to do that in the Gulf when the pesticides were sprayed. Malathion, which the Ministry of Defence had already admitted taking to the Gulf, is regarded as one of the safest OPs. It can be bought over the counter in chemists' for head lice and is a garden pesticide. Dr Jamal said the warnings in the leaflet which accompanies the head lice product were inadequate.
Dimethyl phosphorothionate, otherwise known as fenitrothion, and azamethiphos are spray insecticides - the latter for killing flies in livestock houses, and Diazinon for use in sheep-dips.