What serious health condition can excessive nitrate levels cause in infants?

Excessive nitrate levels in drinking water can lead to a serious health condition known as methemoglobinemia in infants. This condition is often referred to as "blue baby syndrome." When nitrates are consumed, they can be converted to nitrites in the body, which then interfere with the ability of red blood cells to carry oxygen. This is particularly dangerous for infants because their digestive systems are more mature in converting nitrates to nitrites, and their hemoglobin is more susceptible to this conversion.

The symptoms of methemoglobinemia include a bluish tint to the skin, particularly on the lips and extremities, which indicates a lack of oxygen in the bloodstream. It is crucial for caregivers to monitor and manage the levels of nitrates in drinking water for young children to prevent this potentially life-threatening condition.

The other options, while serious conditions in their own contexts, do not directly result from high nitrate exposure in infants. Acute respiratory failure is unrelated to nitrate exposure; cyanosis is a symptom of methemoglobinemia rather than a separate condition; and dehydration, though concerning, is not caused specifically by nitrate levels. Therefore, methemoglobinemia is the correct response regarding the health risks associated with excessive nitrate levels in infants.