Toxic Metals In Soils Threaten Billions Of People

Map showing where soil pollution by toxic metals is exceeding agricultural thresholds.

HOU et al. 2025/Science

Toxic and harmless metals are ubiquitous in soils, yet their worldwide distribution is still poorly known. A research team led by Hou Deyi from the School of Environment at Tsinghua University, Beijing, helped by artificial intelligence, mapped the distribution of potentially toxic metals like arsenic, cadmium, cobalt, chromium, copper, nickel and lead at 796,084 sampling points from 1,493 regional studies.

The resulting map reveals a previously unrecognized high-risk, metal-enriched zone in low-latitude Eurasia.

Combing the map with data on land use and population density shows that 14 to 17 percent of cropland is affected and the researchers estimate that between 0.9 and 1.4 billion people live in regions with soils dangerously polluted by toxic metals.

Pollution by toxic metals is complicated and depends on a variety of environmental factors. Some metals like chromium and nickel can derive from weathering of basalt, a type of volcanic rock quite common worldwide, and some metamorphic rocks. Copper is an essential micronutrient for plant growth and human and animal health found naturally in soils, but at higher levels it can be toxic. Lead can also become toxic at higher levels and is often found in water. Arsenic-bearing aquifers are common in some sedimentary rocks. Human activity, ranging from mining, industrial production, transportation and military operations, can release many different metals into the environment.

High temperature, precipitation, and evaporation rates likely contribute to relatively high metal exceedance in southern China, India, the Middle East, Central America, and Central Africa. Such conditions accelerate the weathering processes that release metals from the bedrock and enhance the enrichment of metals in clay minerals. A warm and wet climate also benefits plant growth, and such subtropical climate zones are essential for global agriculture.

Mining and smelting activities are major contributors to metal pollution, but surprisingly, also agriculture. The proportion of irrigated land was also found to be a strong predictor of metal levels exceeding safe thresholds. Water contaminated by industrial activities and inadequate wastewater treatment can lead to widespread contamination of agricultural soils.

Long-lasting soil pollution can have a profound impact on global food security and public health. Contamination by toxic metals in crops and farm animals can affect biodiversity and productivity. In humans, being on the top of the food chain, the accumulation of toxic metals can cause detrimental health effects and exacerbate poverty.

The authors urge policy-makers and farmers to take immediate and necessary measures to better protect the world’s precious soil resources.

The study,“Global soil pollution by toxic metals threatens agriculture and human health,” was published in the journal Science.

_{Images are for reference only.Images and contents gathered automatic from google or 3rd party sources.All rights on the images and contents are with their legal original owners.}