Study: Agricultural land contaminated with heavy metals - over 1 billion people at risk

Between 14% and 17% of the world's agricultural land is contaminated with at least one toxic heavy metal, warns a study published in the journal Science and cited by AFP. This contamination could pose a direct risk to the health of up to 1.4 billion people. The study provides an unprecedented overview of heavy metal pollution, thanks to a meta-analysis of over 796,000 soil samples and the use of artificial intelligence algorithms to extrapolate data globally.

• Toxic metals above permissible limits

Researchers, led by Deyi Hou, an environmental scientist at Tsinghua University in China, analyzed seven heavy metals - including arsenic and cadmium - and identified areas where their concentrations exceed the recommended limits for agricultural use and human health safety. "Heavy metals can seriously affect humans, flora and fauna, contaminating ecosystems through soil, water and the food chain," warn the study's authors. The results suggest that between 900 million and 1.4 billion people live in areas at high risk of contamination.

• Natural and anthropogenic sources

Soil contamination can be of both natural and human origin. Heavy metals can occur naturally in rocks and soils, but dangerous concentrations are often the result of industrial activities, waste disposal, pesticide use, mining activities or intensive agriculture. However, the researchers acknowledge the limitations of the study. In many parts of the world - particularly Africa - there is a lack of data to allow for a detailed risk assessment. "These results do not yet allow for the implementation of targeted mitigation programs, but should be seen as a wake-up call for policymakers and farmers," the research team says.

• The situation could be worse

According to Wakene Negassa, a soil chemist at the James Hutton Institute in Scotland, the true extent of global heavy metal contamination could be significantly underestimated. "Due to the lack of data and likely underestimation, global soil pollution could be much worse than the current study indicates," he says.

The researchers are calling for more rigorous monitoring and international policies to protect agricultural soils, drawing attention to an insidious phenomenon that could affect global food security and public health.