Groundwater Contamination in India: Excessive Nitrates and Emerging Concerns

Sub: Env

Sec: Pollution

Why in News

A recent report by the Central Groundwater Board (CGWB) highlights the alarming rise in excessive nitrate levels in groundwater across India, increasing from 359 districts in 2017 to 440 districts in 2023.

Nitrate Contamination:

About 56% of India’s districts reported nitrate levels exceeding the safe limit of 45 mg per litre in groundwater.
Sources:
- Excessive use of synthetic nitrogenous fertilizers in agriculture.
- Improper disposal of human and animal waste.
- Industrial effluents and sewage discharge.
Health Impacts: Methemoglobinemia or “blue baby syndrome” in infants. Potential links to certain cancers and thyroid disorders.
Highest Nitrate Contamination: Rajasthan > Karnataka > Tamil Nadu.
Central and southern states, such as Maharashtra (35.74%), Telangana (27.48%), Andhra Pradesh (23.5%), and Madhya Pradesh (22.58%), show increasing trends in contamination.
Monsoon rain exacerbates nitrate contamination, with contamination levels rising from 77% in the pre-monsoon period to 32.66% post-monsoon.
The excessive use of subsidized synthetic nitrogenous fertilizers in agriculture is the major contributor to nitrate contamination.

Fluoride Contamination:

Sources:
- Natural geological formations rich in fluoride-bearing minerals.
- Industrial activities releasing fluoride compounds.
High fluoride concentrations are a major concern in Rajasthan, Haryana, Karnataka, Andhra Pradesh, and Telangana.
Health Impacts:
- Dental fluorosis: discoloration and pitting of teeth.
- Skeletal fluorosis: joint pain, stiffness, and bone deformities.
Mitigation Measures: De-fluoridation of drinking water using techniques like activated alumina adsorption.

Uranium Contamination:

Twelve Indian states have uranium levels beyond permissible limits in their groundwater.
Rajasthan and Punjab recorded the highest number of samples with uranium levels above 100 ppb (parts per billion), far exceeding the safe limit of 30 ppb.
Sources:
- Natural leaching from uranium-rich granitic rocks into aquifers.
- Over-extraction of groundwater leading to increased uranium mobilization.
- Use of phosphate fertilizers containing trace amounts of uranium.
Health Impacts:
- Nephrotoxicity: impaired renal function and kidney disease.
- Potential bone toxicity and increased cancer risk.
Mitigation Measures: Implementing reverse osmosis (RO) water purification systems. Regulating groundwater extraction to prevent over-exploitation.

Mineral	Sources	Diseases Caused
Arsenic	Contaminated groundwater, mining waste, pesticides, industrial effluents	Arsenicosis, skin lesions, cancer (lung, bladder, skin), cardiovascular diseases
Radon	Naturally occurring in soil and rocks, uranium mines, poorly ventilated buildings	Lung cancer
Lead	Lead-based paints, contaminated water (from old pipes), industrial emissions, batteries	Lead poisoning, developmental delays in children, neurological damage, anaemia, kidney damage
Mercury	Contaminated fish (methylmercury), industrial waste, coal burning	Minamata disease, neurological disorders, kidney damage, developmental issues in children
Cadmium	Industrial processes, batteries, fertilizers, contaminated food and water	Itai-Itai disease, kidney damage, bone demineralization, cancer (lung and prostate)
Copper	Contaminated drinking water (from corroded pipes), industrial waste, certain fungicides	Wilson’s disease (genetic), gastrointestinal issues, liver damage in extreme cases
Chromium	Industrial effluents (tanneries, electroplating), contaminated soil and water	Chromium poisoning, lung cancer, dermatitis, kidney damage
Nickel	Industrial waste, nickel-plated products, jewellery, contaminated soil and water	Allergic dermatitis, respiratory issues, lung and nasal cancers

Groundwater in India:

India is the world’s largest user of groundwater, accounting for about 25% of global extraction. Approximately 60% of the country’s irrigated agriculture and 85% of rural drinking water depend on groundwater sources.
According to the Central Ground Water Board (CGWB), 14% of India’s 7,089 groundwater assessment units are classified as over-exploited, with an additional 4% deemed critical.
Studies reveal a net loss of approximately 450 cubic kilometres of groundwater in north India between 2002 and 2021, equating to a depletion rate of about 1.5 cm per year.

Central Ground Water Board (CGWB):

The CGWB, a multidisciplinary scientific organization under the Ministry of Jal Shakti, was established in 1970. It comprises experts in hydrogeology, geophysics, chemistry, hydrology, and engineering.
Conducts surveys and evaluations to map and quantify groundwater resources across India.
Maintains a network of observation wells to monitor groundwater levels and quality.
Through the Central Ground Water Authority (CGWA), it regulates and controls groundwater development and management.