What physiological condition can result from high levels of nitrates?

High levels of nitrates in drinking water can lead to a physiological condition known as "blue baby syndrome," or more formally, methemoglobinemia. This condition primarily affects infants under six months of age, where the presence of excess nitrates in the bloodstream converts hemoglobin into methemoglobin. Methemoglobin is unable to carry oxygen as efficiently as normal hemoglobin, resulting in a reduced oxygen supply to the body's tissues. This manifests as a bluish tint to the skin, particularly around the lips and extremities, hence the name "blue baby syndrome."

Many communities monitor nitrate levels in their water supply due to this significant health risk. While excessive nitrates may also contribute to other health issues, blue baby syndrome is the most direct and severe consequence related to high nitrate concentrations, especially in vulnerable populations like infants.