Soil and water pollution is an increasing problem in China. Soil contamination occurs in most countries with a lot of farmland, heavy industry and mining. In Ukraine, for example, which has all three, about 8% of the land is contaminated. However, China is the world’s largest producer of food and of heavy industrial commodities such as steel and cement.
China’s soil contamination is so great that it is impossible to remove all the contaminants. The country has many brownfield sites (contaminated areas near cities that were once used for industry) but large amounts of polluted farmland, too. In 2014 a government survey showed that 16.1% of all soil and 19.4% of farmland was contaminated by organic and inorganic chemical pollutants and by metals such as lead, cadmium and arsenic.
That amounts to roughly 250,000 km2 of contaminated soil, equivalent to the arable farmland of Mexico. Cadmium and arsenic were found in 40% of the affected land. Up to 35,000 km2 of farmland is so polluted that no agriculture should be allowed on it at all.
However, the head of the Institute of Geographic Sciences and Natural Resources Research in Beijing, thinks 10% (c. 25,000 km2) is nearer the mark. Even that is worrying figure, as China is trying to feed a fifth of the world’s population on a tenth of the world’s arable land.
There are three reasons why the contamination is so extensive. First, China’s chemical and fertiliser industries were poorly regulated for decades and the soil still stores the waste that was dumped on it for so many years. To make matters worse, the ‘safety’ record of the chemical industry is poor. Between January and August 2016, China suffered 232 accidents in chemical factories, such as leaks, fires and explosions—almost one a day. Around 20% of these factories are in China’s most productive agricultural areas or near rivers used for irrigation, many of the spilled chemicals end up in fields.
Cadmium is released during the smelting of ores of iron, lead and copper. It is a heavy metal. If ingested, the liver and kidneys cannot get rid of it from the body, so it accumulates, causing joint and bone disease and, sometimes, cancer.
Hunan province is the country’s largest producer of rice. It also has the most cadmium in its soil. Some rice in Hunan contained 50% more cadmium than allowed under Chinese law.
The second big problem is that land is being poisoned by ‘sewage irrigation’. Wastewater and industrial effluent are used in increasing amounts for irrigation because there is not enough fresh water to go round. China produces over 60bn tonnes of sewage a year and in rural areas only 10% of it is treated. Most of the sludge goes into lakes and rivers, and thence onto fields. A study in 2010 found that water along 18% of the length of China’s rivers was too polluted for use in agriculture.
To make matters worse, the soil is bearing the burden of the excess use of fertiliser and pesticide, which has increased as China’s demand for grain has risen. Since 1991 pesticide use has more than doubled and the country now uses roughly twice as much per hectare as the worldwide average. Fertiliser use has almost doubled, too.
Third, soil pollution is affecting more people than it used to because of economic change and urbanisation.
There may be a link between soil pollution and China’s ‘cancer villages’, 400-450 clusters with unusually high levels of liver, lung, esophageal and gastric cancers.
However, the cost of a clean-up is exhibitive. When London cleared a former industrial area, for the 2012 Olympic games: it cost £3,000 ($3,900) per cubic metre. Cleaning China’s 250,000 square kilometres to the depth of one metre to the same standard would in theory cost $1,000 trillion – more than all the wealth in the world. Even a less thorough clean up would cost more than China could afford.