What potential health issue arises when babies consume nitrates from fertilizer runoff?

When babies consume nitrates from fertilizer runoff, the primary health concern is methemoglobinemia, commonly referred to as "blue baby syndrome." Nitrates can be converted into nitrites in the gastrointestinal tract, which then interferes with the ability of hemoglobin in the blood to carry oxygen. This is particularly dangerous for infants, as their blood chemistry and the functioning of their immature digestive system make them more susceptible to this condition.

In methemoglobinemia, the modified hemoglobin cannot effectively deliver oxygen to the body's tissues, leading to symptoms such as a bluish discoloration of the skin (cyanosis), shortness of breath, fatigue, and in severe cases, brain damage or even death. This condition highlights the critical importance of monitoring water sources for nitrate levels, especially in areas where fertilizer runoff may contaminate drinking water.

The other health issues presented, while serious, are not directly linked to nitrate consumption. Osteoporosis is a bone condition usually related to calcium and vitamin D deficiencies or hormonal changes, lead poisoning is associated primarily with exposure to lead (often through contaminated water or paint), and respiratory disorders generally stem from different causes such as environmental pollutants or infections rather than nitrate ingestion.