Fine particulate air pollution – UGC NET Question

PM2.5 refers to particulate matter with an aerodynamic diameter of 2.5 micrometres or less. These particles can be solid or liquid and remain suspended in the air. Because of their very small size, they can penetrate deep into the respiratory system, reaching the bronchioles and alveoli, and are associated with serious health problems. Thus, the technically correct description is given in option B.

Option A:
Option A is incorrect because PM2.5 refers to particles, not gases. Gaseous pollutants like sulphur dioxide or nitrogen oxides are categorised separately in air quality monitoring.

Option B:
Option B is correct as it clearly states that PM2.5 includes both solid and liquid particles whose diameter is less than or equal to 2.5 micrometres. This definition matches how PM2.5 is defined in environmental science and air pollution regulations.

Option C:
Option C is incorrect since coarse dust particles visible to the naked eye are generally larger than 10 micrometres. PM2.5 is fine particulate matter that is not usually visible individually to the naked eye.

Option D:
Option D is incorrect because ozone is a gaseous molecule and not classified as particulate matter. While ozone can be an air pollutant at ground level, it is not PM2.5.