The WHO permissible limit for fluoride in drinking water is 1.5 mg/L. At concentrations between 3–5 mg/L, which clinical manifestation is most characteristic?

• A Blue baby syndrome (methaemoglobinaemia)
• B Dental fluorosis (mottling of enamel)
• C Arsenicosis (hyperpigmentation and keratosis)
• D Skeletal fluorosis (crippling) ✓

Explanation

Fluoride toxicity is dose-dependent: at 0.5–1.5 mg/L: optimal (caries prevention); at 1.5–3 mg/L: dental fluorosis (mottling of enamel — chalky white to brown staining); at >3–6 mg/L: skeletal fluorosis begins; at very high levels (>10 mg/L): crippling skeletal fluorosis with ligament calcification, osteosclerosis, and genu valgum/varum. Blue baby syndrome is caused by nitrates (methaemoglobinaemia), not fluoride. Arsenicosis is from arsenic contamination.

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.