The consumption of water containing high levels of nitrate–N can lead to

Correct option is A

The correct answer is (A) Methemoglobinemia in infants

Explanation:
• Methemoglobinemia, commonly known as 'Blue Baby Syndrome', occurs when nitrates in drinking water are ingested and converted into nitrites by bacteria in the digestive system.
• These nitrites react with hemoglobin (the oxygen-carrying protein in blood) to form methemoglobin.
• Methemoglobin cannot bind to or transport oxygen effectively. This leads to a decrease in the oxygen-carrying capacity of the blood, resulting in a bluish tint to the skin (cyanosis), especially in infants.
• Infants under six months of age are particularly vulnerable because their digestive systems are less acidic, which favors the conversion of nitrate to nitrite.
• The World Health Organization (WHO) and various national agencies set strict limits (typically 10 mg/L of Nitrate-N) to prevent this condition.

Information Booster:
• High nitrate levels in water are often caused by agricultural runoff (excessive nitrogen fertilizers), septic tank leaks, or industrial waste.
• Boiling water does not remove nitrates; in fact, it concentrates them by reducing the volume of water through evaporation.
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Additional Knowledge:
• Night blindness (Option B): Caused by a deficiency of Vitamin A (Retinol).
• Colour blindness (Option C): Usually a genetic condition affecting the cone cells in the retina.
• Scurvy disease (Option D): Caused by a deficiency of Vitamin C (Ascorbic acid).