Which statement best defines pollution?

• A. Any substance that detracts from natural environmental quality, upsets the senses, or causes a health hazard.
• B. A temporary fluctuation in environmental conditions with no health impact.
• C. An improvement in water quality through treatment.
• D. Natural background levels of chemicals in the environment.

Answer: (A)

Pollution means anything introduced into the environment that degrades its quality, affects the senses, or creates a health hazard. In water quality work, this captures contaminants that can make water taste or smell bad, look cloudy or discolored, or pose risks to health when present at concerning levels. The other statements describe situations that are not pollution: a temporary fluctuation with no health impact is just natural variability, not a contamination problem; an improvement in water quality through treatment is the opposite of pollution, since treatment reduces contaminants; and natural background levels of chemicals exist regardless of human activity and aren’t pollution unless they become harmful or are caused by human factors. So the description that ties together aesthetics and health risk best defines pollution.