Which term refers to harmful substances in water that can render it unsafe for drinking or aquatic life?

The term that best describes harmful substances in water that can make it unsafe for drinking or for aquatic life is "pollutants." Pollutants encompass a wide variety of harmful substances, including chemicals, pathogens, and physical agents that disrupt water quality and can have detrimental effects on both human health and the environment.

While "contaminants" is a general term describing any undesirable substance that may be present in water, it does not specifically convey the harmful nature of these substances as effectively as pollutants do. Contaminants can also include naturally occurring substances that are not harmful, thus diluting the focus on safety.

"Toxins" refers specifically to poisonous substances produced by living organisms or as a result of natural processes. While toxins certainly can be pollutants, the term is narrower in scope than what is typically represented by pollutants.

"Nutrients," although essential for aquatic ecosystems, can also lead to water quality problems like eutrophication when present in excess. However, nutrients in appropriate levels are not considered harmful to drinking water or aquatic life in the same way that pollutants are.

In summary, pollutants is the most fitting term for harmful substances that compromise water safety, as it captures the broad range of detrimental impacts these substances can have on both human health and aquatic