According to WHO and BIS standards for drinking water quality, what is the permissible limit of fluoride in drinking water in India, and what is the maximum permissible limit in the absence of an alternative source?

• A Permissible: 1.0 mg/L; Maximum: 1.5 mg/L ✓
• B Permissible: 0.5 mg/L; Maximum: 1.0 mg/L
• C Permissible: 1.5 mg/L; Maximum: 3.0 mg/L
• D Permissible: 0.6 mg/L; Maximum: 1.2 mg/L

Explanation

BIS IS 10500:2012 (India's drinking water standard) sets the permissible limit for fluoride at 1.0 mg/L in drinking water. In the absence of an alternative source, the maximum permissible limit is 1.5 mg/L (consistent with WHO guideline value). Levels above 1.5 mg/L cause dental fluorosis; chronic exposure above 3–4 mg/L leads to skeletal fluorosis. The optimal level for dental caries prevention in tropical India is approximately 0.5–0.8 mg/L — below 0.5 mg/L increases dental caries risk while above 1.5 mg/L causes fluorosis.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.