I have found that you have to careful. Sometimes it's very obvious with all of them showing black spots. I have friends that travel to China frequently and won't buy their vegetables at the Chinese stores.
China: Millions of hectares of Chinese farmland polluted with heavy metals
Twelve million tonnes of grain must be destroyed. Land and water sources are polluted with heavy metals and other toxic substance. The government pledges quick action, but does not provide details. Given its current drought, China’s food self-sufficiency is in jeopardy.
Beijing – Millions of hectares of farmland have been contaminated with heavy metals and 12 million tonnes of tainted grain have to be destroyed at a time when China’s farming regions are experiencing their worst drought in 60 years. Beijing’s desire for grain self-sufficiency is now at risk because urban sprawl is gobbling up farmland and pollution is making large sections of land unfit for agriculture.
The revelations were made in yesterday's edition of the China Economic Weekly, a magazine controlled by the People's Daily, the Communist Party’s newspaper, which reported on Tuesday that water used for irrigation in Tanggang (Henan) comes from heavily polluted rivers.
An official report also found that up to 10 per cent of rice grown in China was contaminated with toxic metals such as cancer-causing cadmium.
For years, unfettered industrial development has left rivers and farmland in a story state. Now entire areas can no longer sustain farming because of heavy soil pollution. Potential economic losses in terms of contaminated rice would be enough to feed more than 40 million people at a cost of 20 billion yuan.
For many, the authorities, especially at the local level, have tried to hide the problem even though cases of pollution and pollution-related diseases, above all in children, have been front-page news.
http://www.speroforum.com/site/article.asp?id=49148&t=China%3A+++Millions+of+hectares+of+Chinese+farmland+polluted+with+heavy+metals