Nitrate Pollution in Ground Water is A Growing Concern

Nitrate pollution in groundwater is an increasing but silent threat. The new findings by the Central Groundwater Board (CGWB) have painted a dismal picture. The findings point to a significant rise in districts with unsafe nitrate levels in groundwater. There were 440 districts in 2023 where nitrate levels exceeded the permissible limit of 45 milligrams per litre (mg/l). It points to an emerging environmental and public health emergency that must receive immediate attention.

Excessive nitrate in groundwater mainly results from using too many subsidized nitrogenous fertilizers in agriculture. Fertilizers, which are necessary to increase crop yield, seeps into groundwater.  Vulnerable groups, such as small infants, suffer more from these hazards.  Methemoglobinemia or 'blue baby syndrome’, where oxygen transport becomes impaired in infants, is directly related to the increased nitrate concentration in drinking water.

Of the 15,239 samples analysed by CGWB, it was found that 19.8% of the groundwater samples had nitrate concentrations beyond the permissible limit.  However, it is an improvement over the 2017 figure when 21.6% of samples showed contamination.  Adverse effects of the nitrate contamination increase due to dependence on groundwater for drinking water and irrigation.

About half of the samples tested in Rajasthan, Karnataka, and Tamil Nadu exceed the safe limit as these states have the highest nitrate contamination levels. Traditionally, Rajasthan has been a hotspot of nitrate pollution, and the trend has remained relatively constant over the years.

The CGWB report also points out worrisome trends in central and southern states–Maharashtra, Telangana, Andhra Pradesh, and Madhya Pradesh. In fact, 35.74% of samples in Maharashtra showed unsafe levels of nitrate concentrations, indicating a larger regional crisis.

Contamination gets worse in the monsoon as the rainwater increases the infiltration of nitrate into the groundwater reserves. The CGWB data reveals a slight rise in contamination levels just after the monsoon, with 32.66% of the samples having excess nitrate as against 30.77% before the rainy season. Such seasonal variation shows the need for monitoring and mitigation throughout the year to be able to manage the contamination. Apart from nitrate, there are other chemical contaminants like fluoride and uranium which are impairing the groundwater quality throughout India.

The concentration of fluoride in water beyond the permissible limit is one of the most hazardous contaminants in states like Rajasthan, Haryana, Karnataka, Andhra Pradesh, and Telangana. Uranium contamination in soil and water in these states along with Rajasthan, Punjab, Gujarat, and Haryana is more worrisome. More than 30 parts per billion (ppb) nitrate are considered unsafe for health, yet numerous areas are under contamination of more than 100 ppb.

The health effects of these toxins are immeasurable when it comes to long-term exposure to high levels of nitrate. In fact, high levels are associated with conditions like hypertension, severe cyanosis, thyroid gland disorders, and even certain types of cancer. For children, the situation gets even worse as they are much more vulnerable to these deadly poisons than adults. A recent study conducted in Kerala has shown that women and children are at far higher risk than men to nitrate exposure. There are other types of contamination, such from septage in urban areas like Ernakulam and fertilizer runoff in rural agricultural areas like Idukki.

Coastal areas in Kerala like Thrissur and Malappuram and the northern regions of Thiruvananthapuram district ate some of the worst affected zones for nitrate contamination. Their spatial distribution varies, but year upon year, these areas have reported more-than-normal nitrate levels.

The groundwater contamination crisis needs to be addressed through multifaceted approaches. Policymakers should give to regulation of nitrogenous fertilizer use by promoting sustainable agricultural practices. The use of eco-friendly alternatives such as organic fertilizers and integrated nutrient management systems can also help reduce nitrate leaching into the groundwater. Moreover, water quality monitoring systems should also be strengthened in order to proactively detect and address contamination hotspots.

Knowing the risks involved in the nitrate contamination and good water practices could empower communities to take preventive measures. Boiling water or using household water treatment systems are examples of some simple interventions that would probably immensely reduce exposure to harmful contaminants.

Initiatives such as groundwater recharge, rainwater harvesting and afforestation can help in the prevention of contamination. They replenish aquifers, dilute the concentration of harmful substances and improve overall water quality. Preventing groundwater over-extraction is also necessary to avoid aggravated contamination levels. It requires involvement of all the stakeholders, from agriculture to industry, in promoting efficient water use across the sectors.

The CGWB report has shown ray of hope with respect to groundwater levels in India. It says that out of the 1,040 blocks under evaluation, 73% are included in "safe" blocks: these are blocks, according to the report, wherein recharge is adequate to balance the withdrawal. However, it has been observed that out of 1,040 blocks, 343 blocks have not been assessed due to a cut and modified analysis for 2024 compared to that of 2022, which again raises the credibility of such assessment in question.

The increasing concentration of nitrate and other chemicals in water and soils is more than just an environmental issue; it should be seen as a public health emergency with wide-reaching implications. As the silent poison continues to spread beneath us, urgent need for a sustainable water management practices, strong regulatory frameworks, and even wider public awareness have never been more compelling.