Which pollution is responsible for "Knock-Knee-Syndrome"?
- (a)Fluoride
- (b)Mercury
- (c)Arsenic
- (d)Cadmium
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.
- (b)Mercury — Mercury poisoning causes Minamata disease — nervous-system damage (loss of coordination, numbness) — not knock-knee.
- (c)Arsenic — Arsenic contamination causes arsenicosis and black-foot disease, with skin lesions and vascular damage, not genu valgum.
- (d)Cadmium — Cadmium poisoning causes Itai-Itai disease (painful softening/brittleness of bones) — a different bone disorder from fluoride-induced knock-knee.
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.
The tempting wrong answer is cadmium, because Itai-Itai also attacks bone. But 'knock-knee' (genu valgum) is specifically the fluoride / skeletal-fluorosis deformity, whereas Itai-Itai is bone softening and pain, not the inward-bent-knee posture. Anchor the exact symptom to the exact pollutant.
- Fluoride (excess) → dental and skeletal fluorosis; knock-knee (genu valgum) is a skeletal-fluorosis sign.
- Mercury → Minamata disease (nervous system).
- Cadmium → Itai-Itai disease (painful softening of bones).
- Arsenic → arsenicosis / black-foot disease (skin and blood vessels).
- Confusing fluoride's knock-knee (skeletal fluorosis) with cadmium's Itai-Itai — both affect bone
- Thinking fluorosis only harms teeth; excess fluoride also deforms the skeleton
Almost always phrased as 'which pollutant causes disease X' or the reverse. Lock the pairs: F → fluorosis / knock-knee, Hg → Minamata, Cd → Itai-Itai, As → arsenicosis.
People drinking water from a shallow hand pump are likely to suffer from all of the following diseases, except
- (a) Cholera
- (b) Typhoid
- (c) Jaundice
- (d) Fluorosis
Answer(d) Fluorosis
Same theme — fluorosis is the odd one out because it comes from fluoride in the water (a chemical pollutant), not from the pathogens that cause cholera, typhoid and jaundice.
Which pollution causes Itai-Itai disease in human beings?
- (a) Mercury pollution
- (b) Cadmium pollution
- (c) Arsenic pollution
- (d) Nitrate pollution
Answer(b) Cadmium pollution
Same pollutant-to-disease matching skill — this later MPPSC question pairs cadmium with Itai-Itai, the companion to fluoride → fluorosis/knock-knee.
- practice — not a real PYQ
Minamata disease in human beings is caused by pollution of which of the following?
- (a)Lead
- (b)Mercury
- (c)Fluoride
- (d)Nitrate
Answer(b) Mercury — Minamata disease results from methyl-mercury poisoning affecting the nervous system.
- practice — not a real PYQ
Excess fluoride in drinking water primarily affects which parts of the body?
- (a)Teeth and bones
- (b)Liver and kidney
- (c)Lungs
- (d)Skin only
Answer(a) Teeth and bones — causing dental and skeletal fluorosis.