Tiny solid or liquid particles in the air that can enter the lungs.

• A. PM2.5
• B. Ground-level ozone
• C. Particulate matter
• D. PM10

Answer: (C)

Particulate matter refers to tiny solid or liquid particles suspended in the air that can be inhaled into the lungs. It’s the broad category that includes a range of sizes, with smaller particles posing greater health risks because they can travel deeper into the respiratory system. Examples like PM2.5 and PM10 are specific size ranges within this group, describing particles with diameters of 2.5 micrometers or smaller, and 10 micrometers or smaller, respectively. Ground-level ozone is a gaseous pollutant formed by chemical reactions in sunlight, not a particle, so it isn’t particulate matter. That makes particulate matter the best fit for the description.