Which of the following describes a pollutant?

A pollutant is defined as any harmful addition to the environment, which aligns perfectly with the chosen answer. This includes various substances such as chemicals, waste materials, and other contaminants that can negatively affect air, water, soil, and living organisms. The ramifications of pollutants can range from local ecological disruptions to global environmental issues, contributing to health problems in humans and wildlife and altering ecosystems.

The other options do not accurately capture the essence of what constitutes a pollutant. Substances that enhance the environment (the first option) are typically referred to as beneficial or positive additions, which is the opposite of a pollutant. A naturally occurring element (the third option) is not necessarily harmful; many naturally occurring substances are harmless or essential for life. Lastly, a chemical that has no environmental impact (the fourth option) cannot be classified as a pollutant, as pollutants are inherently characterized by their negative effects on the environment.