Excess nitrates in groundwater

As of 2023, 440 districts in India have been identified with excessive levels of nitrates in their groundwater, a significant increase from 359 districts in 2017, according to a report by the Central Groundwater Board (CGWB).  

Key Findings:

• Excessive Nitrate Contamination: 56% of India's districts have groundwater with nitrate levels exceeding the safe limit of 45 mg per liter.
  • The contamination is primarily attributed to the widespread use of subsidized nitrogenous fertilizers used in agriculture, which are a major source of nitrate leaching into groundwater.
• Groundwater Samples with Nitrate Contamination: Out of 15,239 groundwater samples collected across India for testing, 8% had nitrate levels above safe limits.
  • In comparison, 6% of the 13,028 samples tested in 2017 exceeded safe nitrate levels.
• Regional Concerns:
  • States such as Rajasthan, Karnataka, and Tamil Nadu report the highest levels of nitrate contamination, with 49%, 48%, and 37% of their tested samples exceeding the safe limit, respectively.
  • Regions like Maharashtra, Telangana, Andhra Pradesh, and Madhya Pradesh are seeing increasing nitrate contamination, raising alarms.
  • Monsoon rains tend to exacerbate nitrate levels in groundwater, with a slight increase in contamination after the rainy season.
• Other Chemical Contaminants:
  • Uranium contamination in groundwater is another serious issue, especially in Rajasthan, Punjab, Haryana, Karnataka, and Andhra Pradesh.
  • Fluoride contamination is a significant concern in states such as Rajasthan, Haryana, and Karnataka.
• Groundwater Over-Exploitation: The over-extraction of groundwater is also linked to rising uranium contamination, particularly in areas with deeper water extraction.
  • The CGWB report suggests that excessive water extraction in states like Rajasthan, Gujarat, Haryana, and Punjab is exacerbating contamination.
• Groundwater Availability: 4% of groundwater extraction across India is considered sustainable, remaining constant since 2009.
• 73% of groundwater blocks are now classified as safe, a notable improvement from 67.4% in 2022, although fewer blocks were analyzed for the 2024 assessment.

Factors contributing to contamination:

• Naturally Occurring Contaminants: Fluoride, arsenic, nitrate, iron, and heavy metals naturally exist in certain geological formations, affecting water quality.
• Industrial Activities: Untreated or poorly treated industrial effluents discharged into water bodies contaminate surface and groundwater sources.
• Agricultural Activities: Excessive use of pesticides, fertilizers, and agrochemicals in agriculture leads to water contamination over time.
• Sanitation Practices: Inadequate sanitation facilities and open defecation, especially in rural areas, contribute to water source contamination.
• Geogenic Processes: Geogenic processes, such as those causing uranium contamination, can occur naturally, exacerbated by groundwater overexploitation.
• Improper Waste Disposal: Improper disposal of biowaste contaminates groundwater and surface water, increasing the risk of waterborne diseases.

Impact of Groundwater Contamination

• Public Health Risks:Consumption of contaminated groundwater can lead to various health issues, including gastrointestinal disorders, neurological problems, skeletal deformities, and even cancer.
• Common Contaminants and Health Impacts:
  • Arsenic:Chronic exposure can lead to black foot disease and poses significant health risks.
  • Fluoride:High fluoride intake causes neuromuscular disorders, dental deformities, and skeletal fluorosis.
  • Nitrates:Excessive nitrate levels in water can result in methemoglobinemia and blue baby syndrome.
  • Uranium:Elevated uranium levels in drinking water can cause kidney toxicity.
  • Radon:Presence of radioactive radon in groundwater poses risks of lung cancer.
• Economic Burden:Treating water-related illnesses imposes significant healthcare costs on individuals and communities. Productivity losses due to sickness also impact economic development.
• Environmental Degradation: Contaminated groundwater affects ecosystems, harming aquatic life and disrupting biodiversity. It can also degrade soil quality and impair agricultural productivity.
• Social Inequities: Communities reliant on contaminated groundwater often face socio-economic challenges, including limited access to safe drinking water, reduced educational opportunities, and compromised livelihoods.
• Long-Term Consequences: Groundwater contamination can persist for decades or even centuries, posing ongoing risks to human health and the environment. Remediation efforts may require substantial time, resources, and technological interventions.