Which of the following is an airborne contaminant?

• A. Solids on the Ground
• B. Noise
• C. Vapors, Fumes, Gases, Smoke, and Dust in the Air
• D. Water Droplets

Answer: (C)

Airborne contaminants are substances that can be carried by the air and breathed in. Vapors and gases are already in gaseous form and mix with the air. Fumes are tiny solid particles released into the air from processes like heating. Smoke consists of combustion-derived particles, and dust are small solid particles suspended in air. Together, these are the classic examples of what you can inhale because they are in the air you breathe. Solids on the ground stay there unless disturbed, so they aren’t airborne. Noise isn’t a chemical contaminant in the air—it's sound energy. Water droplets can be airborne as aerosols in some contexts, but the option listing vapors, fumes, gases, smoke, and dust in the air best captures the common airborne contaminants.