Which term describes the introduction of substances into the atmosphere that harms health?

• A. Air Pollution
• B. Air Quality
• C. Ozone Layer
• D. Smog

Answer: (A)

Air pollution is the introduction of substances into the atmosphere that harm health. It covers a wide range of pollutants, including gases like nitrogen dioxide and sulfur dioxide, as well as fine particles from vehicle exhaust, industrial processes, and burning. When these substances are present in the air at high enough levels, they can irritate the eyes, nose, and throat, worsen asthma, and contribute to serious cardiovascular and respiratory diseases. Because the question is asking for the general term that describes the process of harmful substances entering the air, air pollution is the most accurate and comprehensive choice.

Air quality, by contrast, describes how clean or polluted the air is at a given time and place, typically measured by pollutant concentrations. The ozone layer refers to the atmospheric layer that protects living things from UV radiation; it’s related to atmospheric chemistry but isn’t the term for the act of introducing pollutants. Smog is a specific type of air pollution—an urban haze formed by a mixture of pollutants—so it’s a particular manifestation rather than the overall concept.