Why in the News?
The United Nations Environment Programme (UNEP), in its latest Frontiers 2025 report titled The Weight of Time, has warned that increased river and coastal flooding caused by climate change could unearth dangerous legacy pollutants from water bodies.
About Legacy Pollutants:
- Definition: Legacy pollutants refer to toxic substances like heavy metals and persistent organic pollutants (POPs) that continue to remain in the environment even decades after their use has been banned or restricted.
- Examples:
- Heavy Metals: Lead, Cadmium, Mercury, Arsenic.
- Persistent Organic Pollutants (POPs):
- Pesticides: DDT (Dichlorodiphenyltrichloroethane), Aldrin, Endrin, Chlordane.
- Industrial Chemicals: PCBs (Polychlorinated Biphenyls), Dioxins, Furans.
- By-products: Produced from incineration, metal smelting, and waste burning.
- Persistence: These substances are highly resistant to environmental degradation and accumulate in riverbeds, lakes, estuaries, and other sediment-rich ecosystems.
- Health Hazards: Even at low exposure levels, legacy pollutants can cause: Neurotoxicity (nervous system damage), Immunotoxicity (immune disruption), Hepatotoxicity (liver damage), Reproductive toxicity (infertility, birth defects), Carcinogenicity (various cancers), Endocrine disruption etc.
- Sources:
- Past industrial practices, use of banned agricultural chemicals, and obsolete pesticide stockpiles.
- Improperly managed chemical landfills, which still hold an estimated 4.8–7 million tonnes of POP waste globally.
Key Highlights of Frontiers 2025: The Weight of Time (UNEP):
- Retreat of Toxins: Climate change-induced flooding can unearth and redistribute toxic legacy pollutants from contaminated sediments into the environment and food chain.
- How? Floodwaters re-suspend heavy metals and POPs trapped in sediment.
- Case Studies Cited:
- Hurricane Harvey (Texas, 2017): Released mercury and carcinogenic chemicals from flood-induced sediment dispersal into Galveston Bay.
- Niger Delta Floods (Nigeria, 2012): Mobilised Polycyclic Aromatic Hydrocarbons (PAHs) from oil-contaminated sediments.
- Pakistan Floods (2010 & 2022): Washed away obsolete pesticide stockpiles, spreading DDT and other POPs into floodwaters and soils.
- India-Specific Findings:
- Sediments of Ganga, Hindon, and Vaigai Rivers show dangerously high levels of Cadmium.
- Cadmium is a known carcinogen and endocrine disruptor, with potential to cause kidney, bone, and reproductive harm.
- Ayad and Vaigai Rivers also showed up deadly levels of Lead concentration.
| [UPSC 2016] Which of the following can be found as pollutants in the drinking water in some parts of India?
1. Arsenic 2. Sorbitol 3. Fluoride 4. Formaldehyde 5. Uranium Options: (a) 1 and 3 only (b) 2, 4 and 5 only (c) 1, 3 and 5 only* (d) 1, 2, 3, 4 and 5 |
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