An international team of researchers led by Tsinghua University's School of Environment in Beijing, China have warned that there is a serious threat to food security and human health due to the presence of toxic metals in agricultural land.
Publishing their findings in Science, the researchers analysed global databases of arsenic, cadmium, cobalt, chromium, copper, nickel, and lead soil pollution at 796,084 sampling points from 1493 regional studies. Machine learning techniques were used to map areas where the presence of these metals had exceeded designated limits for agricultural and human health thresholds.
The researchers conclude that some 14% - 17% of cropland exceed the agricultural thresholds for metals such as arsenic, lead, and cadmium. The study also identified a previously previously unrecognised high-risk zone stretching across southern Europe, the Middle East, and South Asia.
The researchers noted that the contamination is linked to both natural geological processes and centuries of industrial activity, including mining and smelting.
Professor Steve Magrath, at Rothamsted Research who was part of the multi-institute research team, said: "Soil pollution is not just an environmental issue—it directly affects human health and global food security. Protecting our soils is as important as protecting our air and water. Without clean soil, we cannot produce safe food."
Cadmium was identified as the metal exceeding agricultural thresholds by the largest amount. These high levels were found in northern and central India, Pakistan, Bangladesh, southern China, southern parts of Thailand and Cambodia, Iran, Turkey, Ethiopia, Nigeria, South Africa, Mexico, and Cuba. However, considering all the metals investigated the areas most at risk included southern China, northern and central India, and the Middle East. The researchers said that limited data existed for Africa, and predictions would require more soil sampling and analysis for verification.
By overlaying the human health and ecological risk map over global population distribution in 2020, it is estimated that 0.9 to 1.4 billion people live in the high-risk areas. But researcher note that the actual risks posed by soil metals are dependent upon their mobility, overall bioavailability, and human exposure pathway dynamics.
Welcoming the ongoing global initiative on soil pollution prevention and restoration under the United Nations Environment Programme (UNEP) and the Food and Agricultural Organisation (FAO), the researchers suggested that international aid should be allocated to facilitate soil pollution surveys in data-sparse regions such as sub-Saharan Africa.
During 2024, the European Parliament adopted its position for the European Union’s first Soil Monitoring Law, which is aimed at ensuring the EU has healthy soils by 2050. The new law will oblige EU countries to first monitor and then assess the health of all soils on their territory. MEPs are proposing a five-tier classification system to assess soils health. These tiers are: high, good, moderate ecological status, degraded, and critically degraded. Soils with either good or high ecological status would be considered healthy.
Further reading:
• Soil pollution is threatening global health
• Report sets out case for investing in healthy soils
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