What is the main health risk associated with high levels of nitrates in drinking water?

High levels of nitrates in drinking water are primarily associated with methemoglobinemia, particularly in infants. Methemoglobinemia, often referred to as "blue baby syndrome," occurs when nitrates are converted into nitrites in the body, which then interact with hemoglobin, reducing its ability to carry oxygen. This condition can lead to serious health consequences, especially for young children under six months of age, whose digestive systems are more susceptible to this process.

While nitrates can have other health implications, such as potential links to various types of cancers or effects on adults with certain health conditions, the immediate and significant risk they pose to infants is the interference with oxygen transport in the blood. This physiological response is particularly critical since infants have a higher risk of developing severe symptoms from reduced oxygen levels.

Other choices refer to issues like kidney failure, skin irritation, and respiratory problems, which are not primarily linked to nitrates in drinking water. Instead, these symptoms could be connected to other contaminants or specific health conditions, further emphasizing why methemoglobinemia is the most pertinent concern regarding nitrates in young children.