A cluster of cases of infant methemoglobinemia ('blue baby syndrome') is reported in a village. Investigations reveal contamination of shallow wells with agricultural runoff. The most likely contaminant causing this condition is:
- A Phosphate fertilizer residue
- B Organochlorine pesticides
- C Nitrate (NO₃⁻) ✓
- D Arsenic leaching from aquifer rock
Explanation
Methemoglobinemia in infants ('blue baby syndrome') is caused by high nitrate levels in drinking water (>50 mg/L as NO₃ or >11.3 mg/L as NO₃-N per WHO guidelines). Gut flora in infants (lower gastric acidity allows bacterial colonization) reduce nitrate to nitrite, which oxidizes haemoglobin iron from Fe²⁺ to Fe³⁺ (methemoglobin), impairing oxygen transport. Agricultural runoff containing nitrogen fertilizers (ammonium nitrate, urea) is the primary source. Infants are uniquely vulnerable; adults are protected by higher gastric acidity and greater methemoglobin reductase activity.
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.