As per Indian standards, the acceptable concentration of fluoride in drinking water for prevention of dental caries without causing fluorosis is:

• A 1.5 to 2.0 mg/litre
• B 0.5 to 0.8 mg/litre ✓
• C 2.5 to 3.0 mg/litre
• D Below 0.1 mg/litre

Explanation

The optimal fluoride concentration in drinking water lies between 0.5 and 0.8 mg per litre, which protects against dental caries while avoiding mottling of enamel. Levels above about 1.5 mg per litre cause dental fluorosis, and chronic intake above roughly 4 to 8 mg per day over years causes skeletal fluorosis. Option D represents grossly deficient fluoride, which increases caries risk rather than preventing it. This range is the basis of defluoridation targets under the National Programme for Prevention of 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.