In some parts of India* consumption of underground water causes mottled teeth and bone damage. Which one of the following is responsible for this malady ?

The consumption of underground water with high concentrations of fluoride ions is responsible for dental and skeletal fluorosis in many parts of India [2]. Fluoride is the toxicologically active agent in these cases. Dental fluorosis manifests as the mottling, staining, and pitting of tooth enamel, which is often the first indicator of excessive exposure [1]. Prolonged intake leads to skeletal fluorosis, a crippling malady characterized by the hardening of bones, neuromuscular disorders, and stiff, painful joints [2]. In severe cases, it causes 'Knock-Knee syndrome' and humped back due to spinal cord stiffness [1]. While low levels (0.5-1.0 ppm) are beneficial for preventing dental caries, concentrations exceeding 1.5 ppm are majorly responsible for these health issues [2]. India is one of the 24 nations where endemic fluorosis remains a significant public health concern due to naturally high fluoride levels in groundwater [4].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > ag.l.s.Fluorine > p. 414
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 3. Hazards of ground water pollution: > p. 76
3. [4] https://pubmed.ncbi.nlm.nih.gov/32207100/