Groundwater
There are several factors affecting the fluoride presence like granite, gneissic rocks, and volcanic as well as mountainous area sediments of marine origin. The above‐mentioned rocks are rich in fluoride and are often found beneath the Earth's surface, ultimately leading to groundwater contamination. Alarming high fluoride ion concentrations together with various other toxic and infectious substances present in the groundwater of South and Southeastern Asia are of utmost concern (Ghosh et al. 2013).
Figure 2.1 Sources of fluoride contamination in the environment.
Table 2.1 Fluoride levels reported in different regions.
| Country | Location | Fluoride concentration (mg/L) | References |
|---|---|---|---|
| India | Hyderabad, Andhra Pradesh | 0.38–4.0 | Sreedevi et al. (2006) |
| Ranga Reddy, Andhra Pradesh | 0.4–4.8 | Sujatha (2003) | |
| Karbi Anglong, Assam | 0.4–20.6 | Chakraborti et al. (2000) | |
| Bihar Shallow | 0.1–2.5 | Ray et al. (2000) | |
| Delhi | 0.2–32.5 | Raju et al. (2009) | |
| Gujarat | 0.1–40 | Raju et al. (2009) | |
| Palghat, Kerala | 0.2–5.75 | Shaji et al. (2007) | |
| Chandidongri, Madhya Pradesh | 1.5–4.0 | Chatterjee and Mohabey (1998) | |
| Shivpuri, Madhya Pradesh | 0.2–6.4 | Ayoob and Gupta (2006) | |
| Orissa | 0.1–10.1 | Kundu et al. (2001) | |
| Churu/Dungarpur, Rajasthan | 0.1–14 | Muralidharan et al. (2002); Choubisa (2001) | |
| Kancheepuram, Tamil Nadu | 1–3.24 | Dar et al. (2011) | |
| Tamil Nadu | 0.5–4.0 | Raju et al. (2009) | |
| Cambay, North Gujarat | 0–10 | Gupta et al. (2005) | |
| Varanasi, Uttar Pradesh | 0.2–2.1 | Raju et al. (2009) | |
| Sonbhadra, Uttar Pradesh | 0.48–6.7 | Raju et al. (2009) | |
| Mathura, Uttar Pradesh | 0.6–2.5 | Misra et al. (2006) | |
| Canada | Gaspe, Quebec | 0.05–10.9 | Boyle and Chagnon (1995) |
| Ghana | Nathenje and Lilongwe | 0.5–7.02 | Msonda et al. (2007) |
| Pakistan | Nagar Parkar | 1.13–7.85 | Naseem et al. (2010) |
| Sri Lanka | Dry Zone | 0.02–5.30 | Chandrajith et al. (2011) |
| Iran | Posht‐e‐Kooh‐e‐Dashtestan | 0.7–6.6 | Battaleb‐Looie and Moore (2010) |
| China | Taiyuan Basin | 0.4–2.4 | Li et al. (2011) |
| Germany | Muenster Region | 0.01–8.8 | Queste et al. (2001) |
| Mexico | Hermosillo city, Sonara | 0–7.59 | Valenzuela‐Vasquez et al. (2006) |
2.2.2 Anthropogenic Sources
In many developing countries as well as developed countries, the fluoride concentration present in the environment has been majorly altered by industrial discharge. The main sources of fluoride input into the environment via anthropogenic activities are the aluminum and zinc industry, coal‐burning, brick/clay burning, steel production, oil refining, chemical production, uranium trifluoride, magnesium smelting, ceramic glass and uranium hexafluoride production, enamel manufacturing, and fluoride‐containing fertilizers or pesticide industries (Sujatha 2003). Discharge from industries heavily pollutes the soil and water, as well as vegetation cover around the industry and far away from it. Other than industrial emissions, agriculture runoffs having fluoride‐containing fumigants, fertilizers, and pesticides are some of the other predominant causes of fluoride pollution (Kundu and Mandal 2009; Borah and Saikia 2011). Industries involving coal burning pollute the atmosphere in a small area, and the extent of the pollution depends on the origin and type of coal. It has been estimated that burning of biomass releases 76 Gg fluoride into the air annually (Jayarathne et al. 2014).
2.3 Occurrence of Fluoride in the World and India
2.3.1 World
The quantity of fluoride in drinking water varies around the world as well as region to region depending on the geographical location. Contamination of fluoride ions has been largely illustrated in the groundwater of mainly humid, tropical parts
