What is a key sign that water may not be safe to drink?

The presence of pathogens is a crucial indicator that water may not be safe to drink. Pathogens, which include bacteria, viruses, and protozoa, can cause a range of illnesses when ingested. Contaminated water can harbor these harmful microorganisms, leading to gastrointestinal infections and other serious health issues. Testing water for specific pathogens is essential to ensure its safety for human consumption, as these organisms may not produce immediate observable symptoms in the water itself but can present significant health risks.

While high dissolved oxygen levels and low turbidity can indicate good water quality and the presence of healthy ecosystems, they do not directly correlate with the safety of the water for drinking purposes. A lack of taste and odor can sometimes be misleading, as harmful contaminants may be present even when no noticeable taste or smell is detected. Therefore, the identification of pathogens serves as a pivotal sign that water may not be safe to consume, emphasizing the importance of water testing and treatment methods to ensure public health.