S. Ayoob

Fluoride in Drinking Water: A Review on the Status and Stress Effects

‘Water is life,’ so central to human life, yet over one billion people across the world have no access to safe drinking water. Of late, there has been increasing global attention focused on resolving water quality problems especially in developing countries, as the lack of access to clean water denies the most essential of all rights, the right to life. The latest estimates suggest that around 200 million people, from among 25 nations the world over, are under the dreadful fate of fluorosis. India and China, the two most populous countries of the world, are the worst affected. India is plagued with numerous water quality problems due to prolific contaminants mainly of geogenic origin and fluoride stands first among them. The weathering of primary rocks and leaching of fluoride-containing minerals in soils yield fluoride rich groundwater in India which is generally associated with low calcium content and high bicarbonate ions. The unfettered ground water tapping exacerbates the failure of drinking water sources and accelerates the entry of fluoride into groundwater. Most of the scientific literature substantiates the benefits of low fluoride concentrations in preventing dental decay. However, as a surprising paradox, incidence of dental, skeletal and crippling skeletal fluorosis was reported in India with average fluoride concentrations as low as 0.5, 0.7 and 2.8 ppm respectively. Fluorosis, turns out to be the most widespread geochemical disease in India, affecting more than 66 million people including 6 million children under 14 years age. Though fluoride has spread its tentacles in 36,988 habitations and the number of people falling prey to fluoride poisoning have been steadily increasing, an exact exposure-health relationship is yet to be properly elucidated. There is an essential relation between poverty and fluorosis as malnutrition is found to play an aggressive role in its severity.

A Conceptual Overview on Sustainable Technologies for the Defluoridation of Drinking Water

Water is precious to us, as it supports every spheres of human life. The increasing reports on pollution of this “sacred resource” from different sources show our scant regard to this pivotal issue. People in more than 35 nations across the globe face issues of excess fluoride in drinking water, the intensity and severity of which varies with the environmental settings in terms of their geographical and economical status. It has been observed that very few proven sustainable options are available for fluoride removal, especially in developing countries, where the impact of the issue is highly intense. Though the considerable amount of research undertaken worldwide has thrown up many technologies, each having its own advantages and limitations, a lasting solution is still at large. The coagulation and adsorption/ion-exchange processes are the most widely opted defluoridation techniques practiced in fluoride-endemic areas. The Nalgonda technique and adsorption by bone char, or a combination of both, have been used in many developing countries like India and Tanzania, at both domestic and community levels. The membrane processes assure good quality water, but are “higher technology and higher cost” options for most of the fluoride-endemic nations. Electrochemical techniques are “energy-intensive” options but offer excellent fluoride removal. However, the lack of concise conceptual reviews is visibly felt in defluoridation research, which prompted us to carry out this study. This article highlights the underlying basic principles and processes involved in existing fluoride removal technologies so as to catalyze further research in this area.