Definition:

• Heavy metal pollution refers to the contamination of the environment (air, water, soil, and biota) by toxic metals with high atomic weights and densities >5 g/cm³ that are non-biodegradable and persist for long periods.

Common Heavy Metals

• Lead (Pb), Mercury (Hg), Cadmium (Cd), Chromium (Cr), Arsenic (As), Nickel (Ni), Copper (Cu), Zinc (Zn), Iron (Fe), Manganese (Mn), Cobalt (Co).

Sources of Heavy Metal Pollution

• Industrial Sources:
  • Mining & Smelting: Release of Pb, Cd, Zn, and Cu.
  • Tanneries & Electroplating: Chromium and Nickel contamination.
  • Thermal Power Plants: Fly ash containing Mercury and Lead.
  • Battery Manufacturing: Lead and Cadmium.
  • Paints & Pigments: Lead and Chromium compounds.
• Agricultural Sources:
  • Phosphate Fertilizers: Contain Cadmium.
  • Pesticides & Fungicides: Arsenic, Copper, and Mercury residues.
  • Sewage Sludge Irrigation: Accumulation of multiple heavy metals in soil.
• Domestic & Urban Sources:
  • Electronic waste disposal (e-waste).
  • Plastic additives (e.g., lead stabilizers, cadmium pigments).
  • Plumbing corrosion (lead pipes).

Environmental & Health Impacts

• On Human Health:
  • Lead (Pb): Neurotoxin — affects children’s brain development, causes anaemia and hypertension.
  • Mercury (Hg): Bioaccumulates in fish — causes Minamata disease (neurological damage).
  • Cadmium (Cd): Kidney dysfunction, bone demineralization (Itai-Itai disease in Japan).
  • Arsenic (As): Skin lesions, cancer, cardiovascular issues (notable in Bengal Delta aquifers).
  • Chromium (Cr VI): Carcinogenic, damages liver and kidney.
• On Environment
  • Soil Degradation: Heavy metals reduce soil fertility and microbial activity.
  • Water Contamination: Bioaccumulation in aquatic organisms → biomagnification in food chains.
  • Plant Toxicity: Chlorosis, reduced photosynthesis, stunted growth.

Examples

• Minamata Bay, Japan (1950s): Mercury poisoning due to industrial wastewater.
• Itai-Itai Disease, Japan: Cadmium contamination from mining waste.

Measures by Indian Government

• Environment (Protection) Act, 1986 – umbrella legislation.
• Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016.
• E-Waste Management Rules, 2022 – for recycling and extended producer responsibility (EPR).
• National Green Tribunal (NGT) – enforcing accountability for toxic discharges.
• National Clean Ganga Mission (Namami Gange) – addressing industrial effluents.
• Central Pollution Control Board (CPCB) – monitors heavy metals in rivers and soil.

Global Initiatives

• Basel Convention (1989): Control of transboundary movement of hazardous wastes.
• Stockholm Convention (2001): Indirectly targets persistent pollutants.
• Minamata Convention (2013): On Mercury emissions and trade control (India ratified in 2018).
• UN SDG 12 & 14: Sustainable consumption and reduction of marine pollution.