Answer: Fine particles of dust, soot, chemicals in the air; PM2.5 (under 2.5 micrometers) penetrate deep into lungs and enter bloodstream; cause respiratory and cardiovascular disease.
- A Large dust particles that settle out of the air almost immediately after release and remain clearly visible to the unaided human eye at close range in most textbook accounts
- B Fine particles of dust, soot, chemicals in the air; PM2.5 (under 2.5 micrometers) penetrate deep into lungs and enter bloodstream; cause respiratory and cardiovascular disease
- C The larger PM10 particles are generally considered more harmful to health, while the smaller PM2.5 fraction mostly passes through lung tissue unabsorbed during normal conditions
- D Particulate matter of nearly any size class tends to be found mainly in arid desert regions far away from major cities and industrial centers as generally observed in typical laboratory settings
Correct answer: B. Fine particles of dust, soot, chemicals in the air; PM2.5 (under 2.5 micrometers) penetrate deep into lungs and enter bloodstream; cause respiratory and cardiovascular disease
Explanation: Particulate matter: PM10 (under 10 micrometers) - settles in upper airways; PM2.5 (under 2.5 micrometers) - penetrates deep into alveoli, enters bloodstream. Causes: respiratory disease (asthma, bronchitis), cardiovascular disease (heart attack, stroke), cancer, premature death. Sources: vehicles, power plants, industry, biomass burning.
Sunlight passes through the atmosphere and warms the surface; the surface re-radiates this energy as infrared heat, which greenhouse gases (CO₂, CH₄, water vapour) absorb and trap - a naturally beneficial process that intensifies into global warming as gas concentrations rise from human activity.
Concept context
Pollution, global warming, ozone depletion, deforestation, and sustainability. Important for NEET and general awareness.