What are contaminants in drinking water?

Contaminants in drinking water refer to elements or substances that can adversely affect public health when present in sufficient concentrations. The correct choice identifies these contaminants as substances that pose a threat at specific levels, highlighting that not all substances are harmful in every amount, but can become dangerous when they exceed certain thresholds.

For instance, chemicals, microbial pathogens, heavy metals, and other pollutants can lead to health issues, ranging from mild ailments to severe diseases, depending on their concentration and the susceptibility of the population exposed. Understanding this relationship between the levels of contaminants and health risks is fundamental in water quality management and drinking water safety.

The other options do not accurately reflect the nature of contaminants. Substances required for a healthy water supply suggest a beneficial role rather than a harmful one. Materials with no effect on public health would not be classified as contaminants, since contaminants specifically imply potential risk. Lastly, components of nutritional value do not align with the definition of contaminants, which focuses on harmful impacts rather than beneficial nutritional qualities.