A district faces an outbreak of methemoglobinaemia ('blue-baby syndrome') in infants receiving formula made with well water. The most likely contaminant responsible is:
- A Nitrates exceeding 45 mg/L (as NO₃) ✓
- B Fluoride exceeding 1.5 mg/L
- C Arsenic exceeding 0.01 mg/L
- D Coliform bacteria
Correct answer: A. Nitrates exceeding 45 mg/L (as NO₃)
Explanation
Blue-baby syndrome (infantile methemoglobinaemia) results from high nitrate levels in drinking water (>45 mg/L as NO₃, equivalent to >10 mg/L as NO₃-N). Gut bacteria in infants reduce nitrates to nitrites, which oxidize fetal haemoglobin to methemoglobin, impairing oxygen transport. Adults are less susceptible because adult haemoglobin is more resistant. The WHO guideline for nitrates is 50 mg/L (as NO₃) and for Indian standards is 45 mg/L. Fluoride causes dental/skeletal fluorosis; arsenic causes arsenicosis; coliforms cause enteric infections.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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