Up to 17% of the planet’s farmland can be contaminated by toxic heavy metals, new research finds.
As many as 1.4 billion people live in areas where compounds such as arsenic, cadmium, cobalt, chromium, copper, nickel and lead are at risk in soils. Science.
A team of multinational researchers led by Deyi Hou from Tinshua University in China said toxic heavy metal contamination could emerge from a variety of sources, including both natural and human activities.
Regardless of the source, such pollution poses a threat to both ecosystems and human health, scientists warned. Many of these sustained metals can endanger biodiversity, water quality, crop yield and food safety due to livestock bioaccumulation.
“Soil contamination on Earth by toxic metals has been studied for decades,” the scientists say. “However, there is a lack of quantitative estimates of the impact of soil pollution on soil quality and spatially explicit mapping on global scale.”
To assess the global distribution of toxic metals in soil, the researchers compiled data from 1,493 area studies, including 796,084 samples, to identify locations where concentrations exceed the safety threshold.
Using machine learning and modeling techniques, researchers estimated that 14-17% of the world’s farmland (approximately 600 million acres) are contaminated by at least one toxic heavy metal.
They found that cadmium was the most widespread perpetrator, especially in parts of South Asia and East Asia, the Middle East and Africa.
Research shows that nickel, chromium, arsenic and cobalt also exceed safety thresholds in many regions, resulting in a mix of human activities such as mining and industry.
The researchers also identified a transcontinental “metal enrichment corridor” that they described as extending across low-latitude Eurasia along with the cumulative effects of ancient mining, metal-rich bedrock collapse and time-based leaching.
In total, they estimated between 900 million and 1.4 billion people live in high-risk areas.
Going forward, the authors expressed their hope that their data will “act as a scientific vigilance for policymakers and farmers.”
Stakeholders with this additional information can “take immediate and necessary steps to better protect the world’s precious soil resources,” the researchers added.
