The WHO rates fluoride as one of the primary contaminant checks in drinking water. Fluoride is a compound of fluorine, a common element, and occurs naturally in rocks and minerals. It is from here that fluoride enters groundwater, on which we are now increasingly dependent.
Where would you find fluoride?
Fluoride is naturally present at low concentrations in most natural water sources and in rainwater. Fluoride is particularly found in water bodies near urban areas due to a larger number of industries that produce fluoride-rich waste that can contaminate nearby lakes and rivers or through rainwater catching aerosolized fluoride compounds as industry waste.
In daily life, fluoride is found in drinking water since some countries fluoridate their drinking water in order to prevent dental and bone issues. While there are countries in the world that do not fluoridate their water supply, which could mean that at least their drinking water supply would not be contaminated with fluoride, there also exist cases such as China and India, where the the natural concentration of fluoride is so high, it is harmful.
Fluoride occurs in plants and soil through the use of fluoride-based pesticides in agriculture. It can be found in the air and rain sometimes due to high volcanic activity and burning of fossil fuels by industries.
When is fluoride considered a contaminant in water?
Any chemical compound or element is considered to be a contaminant when it is present in concentrations that exceed their permissible limits, assigned by recognized organizations like the World Health Organization (WHO), internationally, or the Bureau of Indian Standards (BIS) in India, thereby having damaging physical or chemical effects to the system and the surroundings it is present in.
Permissible limits for a chemical vary depending on the use of the water, as drinking water, in agricultural practices, in industries or any other sector. In the case of drinking water, the WHO places acceptable limits of fluoride at 1.5mg/L or 1.5ppm and the Bureau of Indian Standards (BIS) places fluoride acceptance levels in drinking water in India at 1ppm. Places like Andhra Pradesh in India have groundwater fluoride levels as high as 5.8 ppm
How common is fluoride contamination?
Fluoride contamination is especially higher in rural areas where groundwater is the main source of drinking water as compared to cities where water mainly comes from rivers, reservoirs. Apart from geogenic presence, groundwater is more susceptible to fluoride contamination through agricultural soils or land that has excessively been sprayed with fluoride-based pesticides.
What are the effects of fluoride contamination?
Water containing high concentrations of fluoride could percolate through the soil and into the groundwater which could result in contaminated drinking water for that particular area. Since nearly 85% of rural India relies on groundwater as a major source of drinking water, this could negatively impact human health by causing skeletal and muscular diseases such as dental and skeletal fluorosis. Fluoride contamination has adverse effects on soil and plant health as well. If the fluoride from pesticides used excessively on agricultural land, it could result in the land becoming infertile as high concentrations of fluoride have been shown to inhibit the bioactivity of the soil microbes.
Are there any physical signs that my water is contaminated with fluoride?
In most cases, concentrations of fluoride would be too low to effect any physical changes that the naked eye could detect. Investigations on water have arrived at fluoridation as a cause for skeletal and dental fluorosis through tracking symptoms like brown staining or pitting on the teeth as shown in the pictures below, which commonly occurs in children between the ages of 8-10, but can be seen in adults as well. It also presents with stiffness and joint pain which are symptoms of skeletal fluorosis, which, in severe cases can lead to change in bone structure and calcification of ligaments. Both these diseases are caused by the consumption of excess fluoride, most commonly, through drinking water.
Image credits: Basavaraj Shiragumpi
However this is not the best way to find out whether water in a particular region is excessively contaminated with fluoride.
While symptoms of fluorosis are an indicator of fluoride contamination, the proactive, scientific way of ascertaining if your water is contaminated or not is by routinely testing the quality of your water.
Water quality testing is a globally recognised scientific form of detection of contamination in not just drinking water but any water source. It is the best way to make sure of what we put into our body and how to maintain it as well as make informed decisions on how to reduce our own chemical footprints.
But testing does not just hold importance on a personal level but on a global scale as well. 85 million people worldwide lack even a basic drinking-water service, including 144 million people who are dependent on surface water. Of these, it is estimated that upwards of 8 million people die of water related diseases each year Water quality testing can help bring these numbers down if it is implemented effectively throughout communities that are not able to have access to the privilege of clean drinking water.
For more information on why testing is important and how you can test your own water samples, read our article on testing here
 Tscherko, D., & Kandeler, E. (1997). Ecotoxicological effects of fluorine deposits on microbial biomass and enzyme activity in grassland. European Journal Of Soil Science, 48(2), 329-335. doi: 10.1111/j.1365-2389.1997.tb00553.x
 Central Ground Water Board, Ministry of Water Resources, Government of India. Retrieved 17 February 2021, from http://cgwb.gov.in/AQM/NAQUIM.html
 Yadav, K. K., Kumar, S., Pham, Q. B., Gupta, N., Rezania, S., Kamyab, H., Yadav, S., Vymazal, J., Kumar, V., Tri, D. Q., Talaiekhozani, A., Prasad, S., Reece, L. M., Singh, N., Maurya, P. K., & Cho, J. (2019). Fluoride contamination, health problems and remediation methods in Asian groundwater: A comprehensive review. Ecotoxicology and Environmental Safety, 182, 109362. https://doi.org/10.1016/j.ecoenv.2019.06.045
Fluorosis. (n.d.). Retrieved February 04, 2021, from https://www.who.int/teams/environment-climate-change-and-health/water-sanitation-and-health/burden-of-disease/other-diseases-and-risks/fluorosis
Drinking-water. (2019, June 15). Www.Who.Int. https://www.who.int/news-room/fact-sheets/detail/drinking-water
Saha, D., Singh, M., Srivastava, D., & Dwivedi, S. (2014). Concept Note on Geogenic Contamination of Ground Water in India (with a special note on Nitrate) [Ebook] (1st ed., p. 12). Faridabad: Central Ground Water Board, Ministry of Water Resources, Govt of India. Retrieved from http://cgwb.gov.in/WQ/Geogenic%20Final.pdf