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Soil testing
A ground-breaking new study has revealed a previously unrecognised band of soil pollution stretching across southern Europe, the Middle East, and South Asia.
The findings suggest that this vast region, home to some of the world’s most densely populated and agriculturally significant areas, may face much higher risks from toxic metal contamination than previously assumed.
Published in Science, the research is the result of an international effort led by scientists at Tsinghua University.
The team compiled data from nearly 1,500 regional studies and analysed almost 800,000 topsoil samples for levels of seven toxic metals, including arsenic, cadmium, lead, and nickel.
Using machine-learning algorithms, the researchers created predictive maps that show where metal concentrations are likely to exceed thresholds for food safety and human health.
What emerged was striking: a transcontinental toxic corridor running from the Iberian Peninsula and the Balkans through the Middle East and into India, Bangladesh, and southern China.
This zone, they say, is characterised by elevated metal concentrations in the soil, with significant implications for agriculture and public health.
“The corridor was unexpected,” says lead author Deyi Hou. “It symbolises the profound imprint of human activity, from ancient mining to modern industry, on our planet’s soils.”
Cadmium appears to be the most widespread problem across this region, followed closely by arsenic and lead.
High cadmium levels were detected in croplands across northern India, Pakistan, Iran, and parts of Turkey, while lead concentrations were elevated in industrial and urban areas throughout the Middle East and southern Europe.
These metals, even in small doses, can accumulate in the human body over time, leading to serious health problems including cancer, cardiovascular diseases, and developmental disorders in children.
In agricultural settings, they also pose a threat to food security by contaminating crops.
Despite the serious implications, the study’s authors caution that actual health risks depend on a range of local factors.
“Metals behave differently depending on soil conditions,” notes Matthias Wiggenhauser of ETH Zürich, who was not involved in the research. “In some alkaline soils, for instance, toxic metals may be less mobile and therefore less bioavailable.”
Still, the scale of the findings is difficult to ignore. The team estimates that up to 1.4 billion people may be living in areas where soil pollution exceeds safety thresholds, with 14–17% of the world’s farmland affected. That includes key agricultural regions in India, Pakistan and Iran, all vital to global food supply chains.
The researchers argue that more soil monitoring is urgently needed, particularly in developing countries where data is sparse. They call for greater international support for pollution surveys, especially in Africa and parts of Asia that were underrepresented in the dataset.
Their findings also highlight the relevance of recent policy moves. In 2024, the European Parliament proposed the EU’s first Soil Monitoring Law, which mandates the assessment and classification of soil health across all member states. Similar initiatives could help identify high-risk zones and direct resources toward remediation.
“Protecting soils is as important as protecting air and water,” says Professor Steve Magrath of Rothamsted Research. “Without clean soil, we cannot ensure safe food or public health.”
As the world accelerates its transition to green technologies, many of which rely on heavy metals, the authors stress that soil pollution should not be left behind in environmental discussions.
By Jed Thomas
IET 36.3 May
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