Heavy metals are polluting the Cauvery River and its fish, researchers from Tamil Nadu have reported.

About Heavy Metals

• Heavy metals are a group of metallic elements with relatively high densities, atomic weights, or atomic numbers, often defined as having a density greater than 5 g/cm³.
• These elements include both naturally occurring metals and certain metalloids and are characterized by their toxic or poisonous nature at low concentrations.
• Some examples of heavy metals are lead, mercury, cadmium, arsenic, chromium, and bismuth.​

Definitions and Characteristics

• Heavy metals are not always consistently defined: most definitions rely on criteria such as density, atomic number, or specific chemical behavior.
• They tend to be much less reactive compared to lighter metals and have fewer soluble sulfides and hydroxides.
• Many are rare in the Earth's crust but are widely used in industrial, agricultural, and domestic applications.​

Environmental and Health Impacts

• Heavy metals such as chromium, arsenic, cadmium, mercury, and lead are major environmental hazards due to their toxicity and widespread use.
• These metals can interfere with enzymatic processes and are known to cause systemic toxicity, damaging the central nervous system, causing degenerative diseases, and acting as carcinogens (cancer-causing agents).
• Sources of environmental contamination include mining, industrial activities, agricultural runoff, and domestic and pharmaceutical waste.​

Uses and Prevalence
Historically, heavy metals like iron, copper, and tin were used for tools and ornaments, while precious metals such as gold and platinum remain important economically.
Today, heavy metals are utilized in everything from electronics and vehicles to plastics and solar panels. Despite their utility, their misuse and accumulation pose significant risks to human health and ecological systems.​
Key Examples

• Essential nutrients: Iron, cobalt, copper, and zinc (can be toxic in large amounts).​
• Highly toxic: Mercury, lead, arsenic, cadmium (can cause neurological and systemic damage).​
• Environmental sources: Mining, industrial production, agricultural runoff, and weathering.​

Conclusion
Heavy metals, while vital in many industrial and biological functions, must be carefully managed because of their potential toxicity and environmental persistence. Modern concerns focus on contamination, exposure risks, and remediation strategies.

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