Groundwater pollution due to organic micropollutants is becoming a major cause of concern in many parts of the world, where water resources are on the decline. India is the largest user of groundwater and the presence of micropollutants in groundwater has been a growing concern. What do studies on micropollutants in groundwater in India show? A paper ‘Organic micropollutants in groundwater of India—A review’ published in the journal Water Environment Research discusses the extent of groundwater pollution due to micropollutants in India.
What are micropollutants?
Micropollutants are organic or mineral contaminants of anthropogenic as well as natural origin that can be harmful to human health as well as the aquatic environment. They can be found at very low concentrations in water and are generated from industrial processes, pharmaceuticals manufactured for human use and veterinary drugs, personal hygiene products, industrial or household chemicals, detergents, cosmetics, textiles, pesticides, or from micro-substances in coatings or paints etc.
Micropollutants can enter the water cycle directly or indirectly via the urban and domestic and industrial wastewater, hospital effluents, storm water runoffs, and also through agricultural runoffs and manure. They do not break down easily and remain accumulated in the water for a long time. It is very difficult to remove the micropollutants through existing wastewater treatment methods while advanced treatment processes continue to be expensive, energy intensive and substance-specific. Thus the most practical way is to prevent micropollutants from entering the water cycle.
Micropollutants found in groundwater in India
About 80% of the rural population and 50% of the urban population in India uses groundwater for domestic purposes without any treatment.
The study finds that:
The important micropollutants found in groundwater in the country include pharmaceuticals, pesticides, Endocrine disrupter compounds (EDCs), Phthalates and Per‐and Poly‐fluoroalkyl substances (PFAS), surfactants, personal care products, artificial sweeteners.
Pesticide and pthalate concentrations exceed the standard guideline values at a number of locations.
Micropollutant concentrations in groundwater show seasonal variation with high concentrations in groundwater in the monsoons due to leaching of micopollutants from the top soil.
Aquifers with shallow water tables show higher contamination due to micropollutants
Types of micropollutants and regions prone to contamination
Groundwater pollution due to pharmaceuticals
The study finds groundwater in Hyderabad to be polluted with twelve different types of pharmaceuticals, the major ones being cetirizine, ciprofloxacin, enoxacin, and metoprolol. Similarly, pharmaceuticals like diclofenac and pitavastatin can be found in groundwater samples in Punjab, while caffein is a major compound found in groundwater samples from rural, semirural, urban, and industrial regions of the Ganga river basin.
Evidence shows that pharmaceutical compounds can lead to respiratory disorders, cancers, reproductive problems, chronic depression and congenital problems including mental retardation and physical abnormalities, and can also lower productivity of agricultural land, altering agricultural infrastructure and harming aquatic life leading to massive death of livestock and fish cancer.
Endocrine disrupter compounds (EDCs) and surfactants in groundwater
Endocrine disruptor compounds (EDC) include exogenous substance or mixtures that alter the function of the endocrine system and have a negative impact on male fertility triggering birth defects, breast and testicular cancer among humans. However, there are no specific guidelines or regulations for EDC in groundwater.
Two types of EDCs—estrogen receptors (ER), a natural hormone, and glucocorticoid receptors were mainly found in in groundwater samples collected in Mathura, Uttar Pradesh.
Surfactants are mainly used in the production of detergents, hair conditioners, shampoos, fabric softeners and foaming liquids. The maximum concentration of surfactants was found in a semirural region in the southern part of Parganas Kolkata. Surfactants can have a toxic effect on aquatic life and also accumulate in the human body leading to teratogenic and carcinogenic effects in the long term
Phthalates and Per‐and Poly‐fluoroalkyl substances (PFAS) pollute groundwater
Phthalates are chemicals added to polyvinyl chloride (PVC) plastics, paints, cosmetics, wood varnish, and medical supplies to increase flexibility and improve durability. Phthalates may be harmful to fish and other wildlife and may interfere with normal endocrine system functions, reproduction, and development among humans.
High concentrations of Dibutyl phthalate were found at six sites in Mysore, Karnataka.
Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals, the most studied being perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). PFAS are used in a wide variety of industrial products, electronic items, food packaging, fire‐fighting foams, insecticides, adhesives, and paints, as well as coatings for textiles.
Groundwater samples collected from the urban and industrial regions in the Ganga river basin showed high concentrations of perfluorobutanesulfonic acid. Evidence shows that PFAs may interfere with the body’s natural hormones, increase cholesterol levels, affect the immune system and Increase the risk of some cancers .
Personal care products (PCP) and Artificial sweeteners (ASWs) in groundwater
PCPs include shampoo, toothpaste, lotions, hair dyes, colognes, insect repellents, and other such products while ASWs are widely used as table top sweetners and food additives. Both PCPs and ASWs were found in the groundwater in the Ganga basin. However, the impact of PCPs and ASWs on human health is less known as of now.
Pesticides in groundwater
Pesticides consist of a wide range of chemicals including insecticides, herbicides, fungicides and rodenticides used to protect crops from diseases and to increase crop yield. The pesticides found in groundwater in India include:
Organochloropesticides (OCP)are mainly used in agriculture and mosquito control and include dichlorodiphenyltrichloroethane (DDT), endosulfan, hexachlorocyclohexane (HCH), lindane, aldrin, dieldrin, heptachlor, butachlor, atrazine, chlordane, methoxychlor, and toxophane. OCPs can pollute soil, water and air and remain for longer periods in the environment and negatively affect the environment and human health. OCPs can lead to endocrine disruption, cause neuromuscular disorders and are known to be carcinogenic and neurotoxic.
Maximum concentration of endosulfan was found in groundwater in Delhi while the concentration of endosulfan in Kasaragod, Kerala exceeded three times the WHO (2017) and Australian Drinking Water Guideline (ADWG) (2011) values.
Endosulfan is banned in almost all nations, whereas it is still used in India, China, and some other countries.
The maximum concentration of DDT was found in groundwater of Aligarh, Uttar Pradesh while the concentrations of DDT were found to be ten times higher than the WHO (2017) and BIS (2012) guideline values in groundwater at Nagaon and Dibrugarh in Assam and Tiruvallur in Tamil Nadu. High concentrations of HCH and aldrin were found in groundwater in Aligarh, Uttar Pradesh, while that of hepatochlor were found in groundwater at Jaipur in Rajasthan and Parbhani in Maharashtra.
Organophosphorous pesticides (OPP) include Dimefox, Mipafox, Methyl Parathion, Ronnel, enitrothion, Bidrin, Phorate, Fenthion, caumphos, Abate, Dichlorovas, Diptrex, Phosphomidon, Demetox, Oxydemeton-methyl, Malathion, Dimethoate and Trichlorofan. Studies show that prolonged exposure to OPPs can lead to increased risks of cardiovascular and respiratory disease, and cancer. In the case of pregnant women, exposure can result in premature births and have a negative impact on the health of foetus.
Among OPPs, malathions were found in high concentrations in Parbhani, Maharashtra, Delhi, Bijapur, Karnataka and Aligarh and Kanpur in Uttar Pradesh, while parathion, dimethoate, and monocrotophos were found in high concentrations in groundwater samples from Aligarh, Uttar Pradesh, Parbhani, Maharashtra and Hyderabad, Telangana. In both cases, they exceeded the health advisory guideline values given by US EPA (2018) and BIS (2012). Parbhani in Maharashtra and Bijapur in Karnataka showed higher than the safety limit concentrations of chlorpyrifos in groundwater samples in the area.
Way forward
The study argues that the persistence of micropollutants in groundwater at certain locations in the country, especially dangerous ones like pesticides highlights the graveness of the situation and calls on the need to:
- Extend research on the possible presence of micropollutants in more regions of the country and generate more data
- Formulate guideline values for water and strict regulations for all the micropollutants found in water sources in the country
The paper can be accessed here