Which pollution is responsible for "Knock-Knee-Syndrome"?

Question

UnlockIAS · Accepted Answer

Correct — A, Fluoride. Long-term intake of excess fluoride, usually through contaminated groundwater, causes fluorosis; 'knock-knee syndrome' (genu valgum — the legs bend inward at the knees) is a severe skeletal manifestation of chronic fluoride toxicity. It has been reported from high-fluoride belts of India, such as parts of the Nalgonda region of the then Andhra Pradesh.

Why the other options are wrong — (b) Mercury poisoning causes Minamata disease — nervous-system damage (loss of coordination, numbness) — not knock-knee.  (c) Arsenic contamination causes arsenicosis and black-foot disease, with skin lesions and vascular damage, not genu valgum.  (d) Cadmium poisoning causes Itai-Itai disease (painful softening/brittleness of bones) — a different bone disorder from fluoride-induced knock-knee.

Concept: Chronic exposure to particular chemical pollutants in water produces characteristic diseases. Excess fluoride causes dental and skeletal fluorosis — knock-knee (genu valgum) is a skeletal-fluorosis sign; mercury causes Minamata disease; cadmium causes Itai-Itai disease; and arsenic causes arsenicosis / black-foot disease. These pollutant-disease pairs are a staple of general-science questions.

State PCS 2019 Q32 — Environment & Ecology PYQ with Answer

State PCS 2019 Q32 — Environment & Ecology PYQ with Answer