Officials involved in the anti-rodent drive insist that the low-intensity poison they are using is harmless to human health. In the absence of precise chemical details, however, it is impossible to know if the substance really is harmless to humans, in any quantity.

Some Chinese media reports, meanwhile, have raised the concern that the new kind of rat poison being used could even be too weak to do the job, and, if so, the current massive undertaking might have to be repeated with something stronger.

Work teams will spread a total of 200 tonnes of rat bait throughout the area of the future dam reservoir in an effort to reduce the rodent population before the water rises next June and pushes the disease-carrying, grain-eating pests into new settlements on higher ground. Xinhua news agency reported that 120 tonnes of rat bait are being scattered in this first campaign, with the remainder to be distributed in another drive in four months time.

Officials are most concerned about the risk of rodents transmitting deadly diseases such as leptospirosis, an acute infectious illness that can cause kidney failure and meningitis. According to an article in the May 2002 issue of China Three Gorges Construction, published by the Three Gorges Project Corp., an outbreak of leptospirosis occurred after the Geheyan dam was built a decade ago on the Qing River, a Yangtze tributary, killing an unspecified number of people.

The Three Gorges area is infested with rodents, and already "a plague of migrating rats has moved up the hills," Jasper Becker writes in the Christian Science Monitor (Dec. 4). He quotes a restaurant owner in Fengjie as saying: "I don’t mean mice: They are about this big," Hong says, his hands 18 inches apart. "Every night I see them. They get into the bedding tearing up the quilts and stealing all the food they can find."

"Trained sanitary clearance staff" have begun scattering rat bait consisting of "rice soaked with raticide" throughout the area’s demolished towns and new settlements, Xinhua reported on Nov 18. The drug being used contains "ingredients known to have a curing effect on human heart disease," the agency said, adding that the supplier, Shenyang Aiwei Co., says the substance will have only "a very minor environmental impact."

Five thousand "clearance workers" and more than 800 disease-control staff have been trained to distribute the "deadly drug," Xinhua said.

According to experts at the Chongqing Disease Prevention and Control Centre, quoted by Xinhua on Nov. 19, only five kilograms of the unnamed drug are being mixed with 200 tonnes of rice paddy. But the rat bait must be carefully checked to ensure it is genuine ("in case of counterfeit product") and strong enough to kill the rodents, Xinhua said.

Reporters from the Beijing Youth Daily (Beijing qingnian bao) visited the old, deserted towns of Zigui and Badong on Nov. 2 and 3. Although the reporters saw the pink-coloured rat bait placed every five metres throughout the towns, they did not see a single corpse.

The rodents may have gone off to die in their burrows, though this presents another problem. The work teams sent in to distribute the rat bait are meant to return days later to pick up the corpses, to prevent contamination of the future reservoir.

"Workers from local health departments will be sent to collect the dead mice and remaining bait, which would either be burned or buried deep where it could not pollute water sources," Xinhua reported on Oct. 11. But in its Nov. 19 report, the agency warned that the whole undertaking will have to be repeated if the goal of drastically reducing the rodent population is not achieved.

Meanwhile, Hubei province, where the Three Gorges dam is located, has banned the production, transportation, sale and possession of strong rat-poison brands such as "Dushuqiang," "424" and "Yibudao." Violators face heavy fines and even jail terms of up to 15 days, the Hubei Daily (Hubei ribao) reported Dec. 3. So far this year, police in Hubei have seized 3,200 kilograms of "Dushuqiang," closed down 670 enterprises that were producing or selling the rat poison, and punished 857 people, the newspaper said.

The move comes amid growing concern about suicide in China, especially among young rural woman, who have one of the highest suicide rates of any group in the world. A recent article in the British medical journal The Lancet reported that in 62 per cent of 519 suicides in China studied by Canadian physician Michael Phillips and five Chinese colleagues, victims used rat poison or pesticides to kill themselves.

The Chinese media have also reported a recent surge of deliberate food-poisoning incidents around the country involving rat poison. A man accused of spiking food served by a rival restaurant owner was executed after 42 people died and 300 others became ill after eating the poisoned food on Sept. 14 in Tangshan, Jiangsu province.

Earlier this week, the last of 70 children and two teachers poisoned on Nov. 25 at a kindergarten in Wuchuan, Guangdong province, were released from hospital. A doctor who ran another kindergarten and was jealous of the rival facility’s success had snuck into the kitchen and put "Dushuqiang" in the salt, but fortunately all those who fell ill were saved, Xinhua said on Dec. 9.

China’s Ministry of Health says it received reports of 104 "serious food-poisoning accidents" from across the country in the first 10 months of this year.