A significant portion of the world’s arable land—up to 17 percent—is polluted with at least one type of toxic heavy metal, putting the health of up to 1.4 billion people at risk, according to a new global study published on Thursday.
The research, published in the journal Science, marks the first comprehensive global assessment of heavy metal contamination in soils. It is based on a meta-analysis of nearly 800,000 soil samples drawn from a wide range of earlier studies.
Led by environmental expert Professor Deyi Hou from Tsinghua University in China, the study used machine learning to assess where soil contamination exceeds internationally accepted safety thresholds. The focus was on seven particularly harmful heavy metals: arsenic, cadmium, cobalt, chromium, copper, nickel and lead.
The research team took care to exclude any samples collected specifically from known contaminated areas to avoid skewing the results. Instead, the study aimed to present a realistic global picture of contamination levels across croplands.
Using artificial intelligence to interpret the vast dataset, the study found that between 14 and 17 percent of the world’s arable land is tainted by at least one toxic metal. These pollutants are not only harmful to crops and ecosystems but also pose serious health risks to humans and animals via food chains and water sources.
The researchers estimate that between 900 million and 1.4 billion people live in high-risk zones affected by this form of soil pollution.
Sources of heavy metal contamination include both natural geological processes and human activities, such as mining, industrial waste disposal and the use of chemical fertilisers in agriculture.
Despite the alarming figures, the study authors warned that their findings may still underestimate the true scale of the problem. They highlighted a particular lack of reliable data in some parts of the world, especially in Africa, making it difficult to implement targeted mitigation strategies.
The researchers described their findings as a wake-up call for global policymakers and farming communities. “This work is intended as a scientific alert for policymakers and farmers to take immediate and necessary measures,” the authors wrote.
Commenting on the study, soil chemist Wakene Negassa of the James Hutton Institute in the UK noted, “The actual extent of global soil pollution may far exceed what is presented by the authors, due to limited data availability and likely underestimation.”
