Sources and toxicity of fluoride in the environment

Fluoride, a naturally occurring element, exists in combination with other elements as a fluoride compound, and is found naturally in water, foods, soil, and several minerals such as fluorite and fluorapatite. Fluoride normally enters the environment and human body through water, food, industrial exposure, drugs, cosmetics, etc. However, fluoride (F-) contamination in groundwater has been recognized as a serious problem worldwide. The World Health Organization's specified tolerance limit of fluoride in drinking water is 1.5 mg/L. Human disease caused by fluoride manifests itself in three forms: dental, skeletal, and non-skeletal fluorosis. Apart from teeth and bones, the interaction and involvement of soft tissues, organs, and other systems of the body with fluoride leads to non-skeletal fluorosis. It leads to many bone diseases, mottling of teeth, and lesions of the endocrine glands, thyroid, liver, kidney, and other organs. Fluoride ion concentration in drinking water can be easily estimated by UV-Vis spectrophotometer. Various defluoridation techniques have been developed to reduce the fluoride content to the desired level including principally membrane and adsorption processes. Biosorption is still one of the most extensively used methods for defluoridation of drinking water due to it being cost-free or low cost and because of its viability.