Which of the following is NOT considered a priority pollutant?

The choice of organic matter as not being a priority pollutant is based on the established classifications used in environmental regulations, particularly those set by the U.S. Environmental Protection Agency (EPA). Priority pollutants are specific chemicals that are known to be hazardous to human health and the environment and require monitoring and regulation in many contexts, particularly in water quality assessments.

Organic matter, while it can influence water quality by contributing to biochemical oxygen demand (BOD) and subsequent aquatic life health, is not classified as a priority pollutant in the same manner as synthetic or toxic chemicals like hydrocarbons or certain detergents. Hydrocarbons, for example, are derived from fossil fuels and can be toxic to aquatic organisms, thus they are monitored heavily. Detergents, especially non-biodegradable ones, can lead to eutrophication and aquatic toxicity, placing them in the priority category as well.

Salts, often resulting from natural processes or industrial activities, can impact water salinity and therefore aquatic ecosystems but are typically not categorized as priority pollutants in the same critical manner as other more toxic synthetic compounds. Therefore, organic matter’s role is more about general environmental impact rather than direct toxicity or persistent hazard, distinguishing it from the listed priority pollutants.