Which contaminant in water is known to cause hemolysis of red blood cells (RBCs)?

Nitrate is known to cause hemolysis of red blood cells (RBCs), particularly due to its action in the body where it can be converted to nitrite. This conversion can lead to methemoglobinemia, a condition where the iron in hemoglobin is oxidized, reducing the oxygen-carrying capacity of the blood. In young infants, high levels of nitrate in drinking water can especially be harmful, leading to significant health issues due to the resulting reduced ability to transport oxygen. Nitrates originate from various sources, including agricultural runoff and septic systems, making their presence in water a public health concern.

The other contaminants listed, while they can pose health risks, do not have the same direct mechanism leading to hemolysis of RBCs. For instance, aluminum may affect neurological functions, copper can lead to gastrointestinal distress and liver damage at high levels, and cadmium is associated with kidney toxicity and other health effects, but none directly cause hemolysis of RBCs in the manner nitrate does.