PM10 and PM2.5 refer to what characteristic of particulate matter?

PM10 and PM2.5 refer to what characteristic of particulate matter?

• A. Micron size/average diameter
• B. Color and appearance
• C. Chemical reactivity
• D. Origin of the particles

Answer: (A)

Particulate matter categories are defined by particle size. PM10 and PM2.5 specify aerodynamic diameters: PM10 includes particles 10 micrometers or smaller, and PM2.5 includes particles 2.5 micrometers or smaller. This size distinction matters because it determines how long particles stay suspended in the air, how far they can travel, and how deeply they can penetrate the respiratory system. Smaller PM2.5 particles can reach the deepest parts of the lungs and even enter the bloodstream, which is why these size-based categories are used in air quality standards and health assessments. Color, chemical reactivity, or origin aren’t what define these categories.

Particulate matter categories are defined by particle size. PM10 and PM2.5 specify aerodynamic diameters: PM10 includes particles 10 micrometers or smaller, and PM2.5 includes particles 2.5 micrometers or smaller. This size distinction matters because it determines how long particles stay suspended in the air, how far they can travel, and how deeply they can penetrate the respiratory system. Smaller PM2.5 particles can reach the deepest parts of the lungs and even enter the bloodstream, which is why these size-based categories are used in air quality standards and health assessments. Color, chemical reactivity, or origin aren’t what define these categories.