Hello Folks!
A week ago, I had my routine dental check-up and because of my braces which probably contribute to a less optimal oral hygiene, I was found to have a decaying tooth. Thankfully, my dentist said, “You can smear some toothpaste on the affected area at your convenience. The fluoride will help in reversing the decaying process.”
Figure 1: Fluoride in Commercial Toothpaste (Sennebogen, n.d.)
Whenever we think of fluoride, the first thing we would think of would be the fluoride in our toothpaste and our water. However, did you know, excess fluoride concentration in groundwater is a big problem in developing countries like India?
Fluoride on its own in drinking water at moderate level is in fact good for the health. Water fluoridation – the controlled addition of fluoride to a public water supply – mainly helps to prevent tooth decay (5 Reasons Why Fluoride in Water is Good for Communities, 2020). However, excess fluoride intake of more than 1.5mg/l causes the opposite effect on our bones. Known as skeletal fluorosis, excessive accumulation of fluorides in our bones due to high fluoride concentration intake causes pain, weaknesses and bending of bones. The late stages of skeletal fluorosis are permanent and detrimental to the health of an individual.
Causes of Fluoride Contamination in Groundwater
There are many reasons that caused the influx of fluoride into groundwater and they can be largely categorised under natural and man-made causes. Naturally, fluorides are found in minerals and rocks such as fluorite, apatite and micas. During weathering and circulation of water in these rocks and minerals, the fluoride can leech out and dissolve in groundwater. In India, presence of fluoride rich minerals such as fluorite, biotite and hornblende contain 460 to 1706 mg/kg of fluoride. Laboratory studies conducted by (Chae et al, 2006) showed that leaching of fluoride from granitic rocks contributed 6 to 10 mg/l of fluoride to water.
However, fluoride contamination of soil is primarily due to the application of phosphorous fertilizers containing < 1% to > 1.5% fluorine (Bhat, 2015). The types of soils also affect how much fluoride is leeched off into groundwater. Soils with presence of higher clay and oxyhydroxide contents helps to retain more fluoride, preventing them from leeching during heavy rainfall.
Other anthropogenic sources of fluoride pollution in soil also comes from chemical industries such as aluminium and zinc smelting industries. The soil of the areas in the industrial units were measured to have contain medium to high content of fluoride (Bhat, 2015).
Health Effects of Skeletal Fluorosis
Figure 2: Villagers in Tapatjuri Village, India Suffers from Skeletal Fluorosis
As shown in Figure 2, the obvious effect of skeletal fluorosis is deformity in bones and joints. When humans are chronically exposed to high-level of fluoride, these fluorides accumulate in the bones over many years, causing physical changes to the bone structure. The ligaments may calcify resulting impairment of muscles and severe pain (Water-related diseases, 2020).
The sad truth is that in developing countries, such a case of groundwater contamination is rampant. One issue is that while technologies are in place to purify these drinking waters, high cost is always a concern and hence, villagers continue to be exposed to contaminated water. As water is the universal solvent, contamination by fluoride is just one of the many problems these villagers faced.
References:
1. Ada.org. 2020. 5 Reasons Why Fluoride In Water Is Good For Communities. [online] Available at: <https://www.ada.org/en/public-programs/advocating-for-the-public/fluoride-and-fluoridation/5-reasons-why-fluoride-in-water-is-good-for-communities> [Accessed 24 July 2020].
2. Sennebogen, E., n.d. Should Everyone Use Fluoride Toothpaste?. [online] HowStuffWorks. Available at: <https://health.howstuffworks.com/wellness/oral-care/products/fluoride-toothpaste.htm> [Accessed 24 July 2020].
3. Chae, G. T., Yun, S. T., Kwon, M. J., Kim, Y. S., & Mayer, B. (2006). Batch dissolution of granite and biotite in water: Implication for fluorine geochemistry in groundwater. Geochemical Journal, 40, 95-102.
4. Bhat, N. (2015). Assessment of Fluoride Concentration of Soil and Vegetables in Vicinity of Zinc Smelter, Debari, Udaipur, Rajasthan. Journal Of Clinical And Diagnostic Research. doi:10.7860/jcdr/2015/13902.6667
5. World Health Organization. 2020. Water-Related Diseases. [online] Available at: <http://www.who.int/water_sanitation_health/diseases-risks/diseases/fluorosis/en> [Accessed 24 July 2020].
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