The permissible limit of fluoride in drinking water as per IS:10500 (BIS standards) is 1.0 mg/L. At what level does fluoride cause skeletal fluorosis with radiological changes?
- A Fluoride intake > 0.5 mg/day
- B Fluoride intake > 3–6 mg/day for 10+ years ✓
- C Fluoride intake > 10 mg/day for 2 years
- D Any fluoride intake above 1 mg/L causes bone disease
Correct answer: B. Fluoride intake > 3–6 mg/day for 10+ years
Explanation
Fluoride effects are dose- and duration-dependent: at 0.5–0.8 mg/L = optimal (dental caries prevention); at 1.5 mg/L = dental fluorosis (endemic mottling); at 3–6 mg/day for >10 years = skeletal fluorosis (osteosclerosis, radiological changes, 'poker spine'); at higher doses = crippling fluorosis with ligament calcification and neurological compromise. IS:10500 sets the permissible limit at 1.0 mg/L (desirable < 1.0 mg/L). India has widespread endemic fluorosis in parts of AP, Rajasthan, Gujarat, and Punjab due to fluoride-rich groundwater.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.