Around one-sixth of the world’s cropland is contaminated with toxic heavy metals, putting as many as 1.4 billion people at risk, according to new research.

Scientists estimate that 14 to 17% of global cropland—approximately 242 million hectares—is polluted with at least one hazardous metal, such as arsenic, cadmium, cobalt, chromium, copper, nickel, or lead, at levels exceeding safe agricultural and human health limits.

The analysis, conducted by the American Association for the Advancement of Science (AAAS) and published in Science, analysed data from over 1,000 regional studies worldwide and used machine learning to refine the results.

Dr Liz Rylott, a senior lecturer in the department of biology at the University of York, who was not involved in the research, said: “These findings reveal the deeply worrying extent to which these natural poisons are polluting our soils, entering our food and water, and affecting our health and our environment.

“Often collectively called heavy metals, these elements cause a range of devastating health problems, including skin lesions, reduced nerve and organ functions, and cancers.”

Soil contamination from toxic metals comes from both natural processes and human activities. It poses serious threats to ecosystems, human health, crop production, water quality, and food safety, largely due to bioaccumulation in farm animals. Once present, these pollutants can persist in the soil for decades.

With global demand for critical metals rising, researchers warn that soil pollution is likely to become even more severe.

 “Our drive for technology-critical metals to build the green infrastructure required to tackle climate change (wind turbines, electric vehicle batteries and photovoltaic panels) will exacerbate this pollution,” said Rylott.

By integrating pollution data with global population maps, the study estimates that between 900 million and 1.4 billion people are living in high-risk areas.

Cadmium emerged as the most widespread contaminant, with especially high concentrations found in south and east Asia, as well as parts of the Middle East and Africa.

“This map illustrates how metal pollution is independent of human borders; to tackle this problem, countries will have to work together,” said Rylott. “Much of the pollution is in low- and middle-income countries, where communities are directly affected, exacerbating poverty. The effect of these contaminated crops entering global food networks is not as clear.”

 

 

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