A chromium waste pile, in Mou Ding, Yunnan.

Unluckily, just like a very large pile of dirt. Their unassuming appearance means dumped piles of chemical waste can go months unnoticed and unchecked in the countryside of China. But this "dirt" is toxic, possibly cancer-causing, and in order to avoid contamination of our waterways and biosphere must be disposed of properly.

Unfortunately that's exactly what didn't happen earlier this year in Yunnan, a southern province of China. Instead, two truck drivers of Yunnan Luliang Chemical Industry dumped multiple loads of chromium-contaminated waste in the hills of Qilin district in Qujing, near the Chachong Reservoir, over a period of three months starting from April. The two men were destined for Guizhou where the waste was to be disposed of at a processing plant. Instead it was left close to the mouth of a reservoir where nearly 3,000 people live nearby. Many of these people are farmers who depend on the water for their livelihood. In June, a light rain hit the area, washing down parts of the waste to the reservoir. 77 cattle died shortly after drinking the contaminated water. The drivers were arrested and the local environmental authority rushed to the dumping site to clean it up.

But this incident only reveals a much bigger problem. The 5,000 tons of chromium waste came from a chemical company that still owns another 140,000 tons of such waste, which is piling up in a poorly maintained site just meters away from the Nanpan River. It's a situation that immediately became a national concern when reported by the local media. Last month a Greenpeace team headed to the area of the 140,000 ton chromium waste pile. They visited a spot that locals call "the dragon's fountain". It is the mouth of an underground aquifer but ever since the chemical company moved in the water, that's used to irrigate crops and as drinking water by the monks of the local temple, had turned a nasty colour. One farmer told Greenpeace on video that his last rice crop, located near the site, had failed.

When Greenpeace members tested the water some levels of hexavalent chromium (chromium VI) were so high it exceeded the limits of the on-site tester, which could only read up to 1.33 mg/L. Lab results later revealed that two of the sites near the "dragon's fountain", one at the mouth and the other in a rice paddy field close to it read respectively 24.25mg/L and 12.64mg/L of present hexavalent chromium. 0.1mgL is the highest recommended level for irrigation, groundwater and general use. The "dragon's fountain" is not the only water body that was contaminated. The Nanpan River itself is also under threat. Greenpeace members took samples of the river water that runs by the large chromium waste pile and discovered hexavalent chromium at 0.204 mg/L. A control sample at an uncontaminated section upstream was tested at 0.0007 mg/L.

And the problems are hardly restricted to this waste site. In 2005 there were at least 41 piles of chromium waste across 19 provinces, totaling at least four million tons. The Ministry of Environment Protection claim that three quarters of these have since been "neutralized", but one quarter still remain.

View China's chromium waste piles (2005) in a larger map

This includes one at Mou Ding, a site that has remained since at least 2006. As one of the two chromium waste sites in Yunnan province, the waste had been sitting on the site of the since abandoned Mou Ding Yu Dian Chemical Industry. A few scrappy pieces of metal had been hastily used to cover the pile, with only two elderly men quietly overseeing the decaying remains. Several warning signs had been erected, but only after the Chinese media storm that had hit following the recent discovery of these toxic dump-sites.

Greenpeace's concerns are multi-fold. We're concerned about the 140,000 tons of chromium waste that Yunnan Luliang Chemical Industry has yet to dispose of. We're worried that local people are still living and working far too close to the contamination site. There's no clear signage warning local villagers of the dangers, preventing them from using the water in their irrigation or in raising sheep and cattle, and informing them that touching or inhaling this deadly material can lead to serious health damages. We're worried about the bigger picture. There are dozens of chromium waste sites still sitting in 12 provinces across China, some of them located in densely populated areas. And most of all we're worried about the effects of prolonged exposure to this toxic waste.

Last week Xinhua reported, "No human deaths have been attributed to the chromium pollution, but at least 14 local residents have been diagnosed with cancer since 2002 and many suspect their diseases were caused by contaminated drinking water." Such reports led journalists to suspect the existence of "cancer villages", villages that are located in close proximity to chemical factories and turning up unusually high numbers of cancer cases. One such village is Xinglong, just two kilometers from the Luliang dumpsite, and which 17 residents were reported from having already died from cancer in 2009.

(In Chinese) Local farmers discuss the changes that have taken place since the contamination of the water supply.