In India, availability of clean and safe drinking water is miserable. The over-exploitation of available resources has resulted in deterioration of groundwater quality which causes various health problems on consumption. About 70,736 rural habitats with a combined population of 47.4 million live on contaminated groundwater. Major reported contaminants of groundwater are fluoride, nitrate, chloride, arsenic, salinity, heavy metals, etc.
Amongst the various contaminants, fluoride is one of the major contaminant in the groundwater. It has significant health effects both at low and high concentrations in the human body. World Health Organization (WHO) has prescribed the fluoride intake in drinking water as 1.5 mg/L  and consumption above this concentration can cause various health issues. In India, Bureau of Indian Standards (BIS) has prescribed the permissible range of fluoride as 1.5 mg/L.
Health impacts of excess fluoride ingestion
Health problem due to fluorosis is endemic to many countries of the World including China, India, Sri Lanka, Central Africa, and South America. In India, 62 million people including 6 million children are having the problem of fluorosis. Amongst different age-groups, fluoride toxicity is more susceptible to infants and children. This is due to the fact that infants receive up to 400% (per pound of body weight) more fluoride than adults if consuming the same concentration due to their small size. Moreover, the infants can excrete only 15 to 20% of ingested fluoride in comparison to a healthy adult, who can excrete more than 50% of an ingested fluoride.
Past studies have reported that consumption of prolonged and high concentration of fluoride can cause pain in the joints, viz. neck, back, hip, shoulder and knee, nausea, vomiting, pain in the stomach, bloated feeling/gas formation in the stomach, constipation followed by diarrhea, polyurea (tendency to urinate more frequently), etc. Earlier findings further also observed adverse impacts of excess fluoride ingestion on reduced intelligence quotient (IQ).
Fluoride contamination in groundwater can be reduced through in-situ or ex-situ treatment methods.
Ex-situ methods are water treatment methods that include precipitation–coagulation method, which is the most widely used process. The Nalgonda process is widely known precipitation–coagulation fluoride removal method. Adsorption Method involves passage of water through a contact bed where fluoride is removed by ion exchange or surface chemical reaction with the solid bed matrix. The different adsorbents used for fluoride removal include activated alumina, carbon, bone charcoal, activated alumina coated silica gel, calcite, etc.
In situ method is the development of watershed management plan and creating recharge structures that will ensure maximum infiltration of rainwater and help in improving the groundwater quality by dilution and also prevent depletion of ground water table.
Information provided in the article is taken from various literature sources. Author acknowledges the findings of the researchers.
Author: Dr. Ruchi Gupta