Which of the following substances is linked to acute health effects in water?

Nitrates are linked to acute health effects in water primarily because they can lead to a condition known as methemoglobinemia, or "blue baby syndrome," particularly in infants. This condition occurs when the nitrate levels in drinking water exceed safe limits, causing a significant reduction in the ability of blood to carry oxygen. This is a critical health risk, especially for infants under six months old, as their bodies are less equipped to process nitrates effectively. Elevated nitrate levels often stem from agricultural runoff, which makes understanding and monitoring these levels vital for public health, especially in areas with intensive farming practices.

While lead and asbestos are indeed harmful, they tend to cause more chronic health issues rather than acute ones. Lead exposure can result in severe long-term neurological and developmental problems, while asbestos is associated primarily with respiratory diseases and cancer over prolonged exposure. Magnesium does not typically carry acute health risks in drinking water, especially compared to the immediate dangers posed by high nitrate levels. Therefore, nitrates stand out as the substance most directly linked to acute health effects in water.