A joke that has gone viral online goes something like this: An air passenger is forced to take off all his clothes but still sets off an alarm while walking through a metal detector at a foreign airport. At first, the security personnel are puzzled, but then they realize that passenger is from China and thus has an unusually high concentration of heavy metals in his body. The joke reflects Chinese people's frustration with environmental pollution and the health risks it poses.

In fact, there is enough scientific evidence - as highlighted by many netizens - to show that Chinese people are indeed part of a "heavy metal band". For instance, the New York Health Examination and Nutrition Survey reveals that immigrants from the Chinese mainland have "higher blood levels of lead, cadmium, and mercury than either reference group". The report published in the Journal of Immigrant & Refugee Studies also says that the high level of heavy metals in Chinese immigrants is probably associated with their diets, that is, the contaminated food they eat.

While the US report may not be applicable to people across the Chinese mainland, illegal dumping of untreated industrial effluents and the high concentration of heavy metals in some food products have indeed become public health hazards.

Earlier this month, a study found excessive amounts of thallium and cadmium, both carcinogenic heavy metals, in a section of the Hejiang River in Guangdong province, which is the source of drinking water for 30,000 people of Fengkai county. The sources of the contaminants, mining companies in the upper reaches of the river, wereonmental reportedly shut down.

The discovery of cadmium-tainted rice from Hunan province has prompted many people to shun the staple from China's top rice-growing province. About 28,000 hectares, or about 13 percent of paddy land, in Hunan is contaminated by heavy metals, according to official estimates. As a result, the sale of Hunan rice has plummeted and many rice mills in the province have closed down, rendering many people jobless.

Unfortunately, soil contamination is not a problem unique to Hunan. It is a problem facing the entire country. The Ministry of Land and Resources once said that every year about 12 million tons of grain - enough to feed more than 40 million people for one year - is contaminated with heavy metals. It also said that contaminated grain causes a direct economic loss of more than 20 billion yuan ($3.26 billion) a year.