BORDER checks on trucks carrying vegetables have been stepped up in a bid to track down the source of contaminated gau gei that has poisoned 22 people. Eight people have been admitted to Queen Mary Hospital. The others, including a four-year-old, were treated in the casualty department and discharged. The poisoning affected nine families, seven of which are known to have made soup from the vegetable, which they bought at the Sai Ying Pun market in Western. A spokesman for the Health Department said: ''We have taken samples of the vegetable from the market and from a number of vehicles stopped at the border, but so far the results have been negative. ''None of the families were able to give us any remaining food but clinical tests have shown that the food poisoning was almost certainly a result of pesticide contamination.'' The victims suffered mainly vomiting and nausea. Leung Sui-sum, chief health inspector (Western) for the Urban Services Department, said the families had pinpointed one unlicensed hawker in Des Voeux Road West as a possible source. But when officials visited, the hawker had disappeared. Border officials will pay special attention to trucks carrying the vegetable, which is also known as matrimony vine. The Health Department spokesman said: ''Once we find out which farm the vegetable has come from we can pass on the information to the Chinese authorities so they can take action to resolve the problem. ''We do get sporadic cases of vegetables which have been contaminated with pesticide but a much larger number of people seem to be affected this time.'' Mr Leung said there was ''widespread concern among the community'' about unlicensed hawkers, and his officers would be stepping up their patrols. The most effective deterrent was to destroy their food when caught, as fines were only a few hundred dollars, he said. The pesticide is probably methamidophos, a phosphorus-based chemical originally developed for chemical warfare. It is banned in Hong Kong but used on Chinese farms, according to an agriculture expert. ''It's not registered in Hong Kong - it can kill,'' said Chris Chan Chi-chiu, senior agricultural officer at the Agriculture and Fisheries Department. He said humans ''can't tolerate any trace'' of the pesticide. It affects the nervous system, causing sickness, headaches, dizziness, blurred vision, breathing difficulties, and in large doses, paralysis, coma and finally death. No one who has eaten the pesticide on vegetables has died. In China, it was prohibited on vegetables but allowed on more long-term plants such as fruit trees, which meant it was easy to buy, Mr Chan said. It is used to kill cutworms, loopers (a sort of caterpillar), aphids, mites and whitefly. Alfred Clancy, safety and environmental control unit officer at the Hong Kong University of Science and Technology, said the problem was usually that farmers picked the vegetables too soon after spraying it, or applied more than recommended. He recommended washing vegetables with warm soapy water and thorough rinsing. Boiling was better than stir-frying as the pesticide could stay in the oil.
