Context 

A study published in Science has found that contamination of soil by toxic heavy metals and metalloids is substantially lowering agricultural productivity and tainting food supplies worldwide.

Key findings of the study:

Affected area and people

Researchers discovered that 14% to 17% of global agricultural soils contain levels of at least one toxic metal that surpass safe limits. This widespread contamination impacts approximately 900 million to 1.4 billion people residing in vulnerable areas, presenting significant risks to human health, food safety, and ecological balance.

Contaminated Belts

The most severely polluted zone spans across low-latitude regions of Eurasia, covering parts of southern Europe, the Middle East, South Asia, and southern China. This area overlaps with the heartlands of ancient civilizations like the Greeks, Romans, Persians, and early Chinese dynasties. According to the study, the buildup of toxic metals is the result of centuries of human activities—such as mining, metal processing, and farming—alongside natural factors like metal-rich geological formations and low precipitation.

About heavy metal pollution

Heavy metals such as lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As), and chromium (Cr) are naturally occurring elements but become toxic when present in high concentrations due to industrial discharge, mining, fossil fuel burning, wastewater irrigation, and agrochemicals. Unlike organic pollutants, heavy metals do not degrade and persist in the environment, accumulating in soil, water, air, and living organisms.

Environmental Impacts of Heavy Metal Pollution

1. Soil Degradation

• Alters soil pH and kills beneficial microorganisms (e.g., nitrogen-fixing bacteria).
• Leads to loss of soil fertility, affecting crop productivity.
• Reduces soil’s buffering capacity, making it more vulnerable to other pollutants.

2. Water Pollution

• Heavy metals leach into groundwater and contaminate rivers and lakes.
• Accumulates in aquatic ecosystems, harming fish and other marine organisms.
• Contaminated water sources pose risks to drinking water safety (e.g., arsenic in groundwater in West Bengal).

3. Air Contamination

• Emissions from smelting, industrial units, and waste incineration release heavy metals into the atmosphere.
• Particulate-bound metals can travel long distances and settle in remote areas.
• Inhalation causes respiratory issues in humans and animals.

4. Biodiversity Loss

• Toxic to pollinators (like bees) and soil fauna (like earthworms), disrupting ecological balance.
• Accumulates in the food web, causing bioaccumulation and biomagnification.
• Threatens endangered species in contaminated habitats.

5. Disruption of Ecosystem Services

• Impacts nutrient cycling, water purification, and plant growth, weakening ecosystem resilience.
• Contaminated areas become ecologically dead zones (e.g., around mining areas).

Conclusion:

Heavy metal pollution poses a grave threat to environmental sustainability. Its long-term presence and irreversible impacts on soil, water, air, and biodiversity call for urgent regulatory actions, pollution control, and ecological restoration efforts. Tackling this issue is crucial to achieving Sustainable Development Goals (SDGs) related to clean water, life on land, and good health.