UGC NET Questions (Paper – 1)

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.

Fine particulates with diameters less than 2.5 micrometres can bypass the upper respiratory defences and reach the deepest parts of the lungs. From there, some particles or their components can move into the bloodstream. These processes are associated with inflammation, aggravated asthma, heart attacks and other serious health outcomes. Hence, the main reason PM2.5 is considered particularly harmful is its ability to penetrate deeply and affect multiple organ systems, as stated in Option C.

Option A:
Option A is incorrect because many PM2.5 particles are too small to be seen with the naked eye. Their danger lies in their invisibility and ability to reach deep into the lungs, not just in causing eye irritation.

Option B:
Option B is incorrect because fine particles do not simply settle quickly; they can remain suspended in the air for long periods and be easily inhaled. Their persistence in the air increases the duration and likelihood of exposure.

Option C:
Option C is correct as it identifies the key health pathway: deep penetration into the respiratory tract and possible entry into the bloodstream. This ability to affect both the lungs and the cardiovascular system makes PM2.5 especially hazardous.

Option D:
Option D is incorrect since PM2.5 can contain toxic metals, organic compounds and secondary aerosols. These components are far from harmless and have well-documented long-term health impacts.

Statements C and D are wrong, whereas A and B are correct. Statement C is incorrect because indoor air pollution is a major concern in many rural households that use solid fuels such as wood, dung or crop residues for cooking. Statement D is also incorrect because air quality standards are framed primarily to protect human health, although they may also consider welfare, vegetation and materials. Therefore, the correct answer must identify both C and D as wrong statements together.

Option A:
Option A is incorrect because it singles out C only as wrong while ignoring D. Although C is indeed wrong, D is also an incorrect statement since air quality standards explicitly aim to protect human health. Because the question asks for all wrong statements, excluding D makes this option incomplete.

Option B:
Option B is incorrect because it selects D only as the wrong statement and treats C as correct. As indoor air pollution is a serious health issue in many rural areas of developing countries, statement C cannot be accepted as true. Leaving out C from the set of wrong statements makes this option unacceptable.

Option C:
Option C is incorrect because it claims that A, C and D are wrong. Statements C and D are wrong, but statement A is correct because fine particulate matter (PM2.5) can indeed penetrate deep into the respiratory system and reach the bloodstream. Including a correct statement among wrong ones invalidates this combination.

Option D:
Option D is correct because it accurately identifies C and D as the wrong statements and excludes A and B, which are scientifically valid. It recognises that indoor air pollution is a serious rural health issue and that air quality standards serve to protect human health. Hence this combination fully satisfies the requirement of selecting the wrong statements.