Daily Static Quiz Prelims Practice 2027
PM2.5 (particulate matter with aerodynamic diameter ≤2.5 micrometres) is classified as fine particulate matter, and its tiny size lets it bypass the body's natural defences, penetrate deep into the alveoli, and enter the bloodstream — causing cardiovascular disease, stroke, lung cancer, and respiratory illness, unlike the coarser PM10 (≤10 micrometres) which is largely filtered in the upper respiratory tract. Option (a) reverses the size relationship, since PM2.5 is smaller, not larger, than PM10. Option (c) is wrong because PM2.5 is particulate, not gaseous, and is measured in μg/m³, not ppm. Option (d) is wrong because PM2.5 and PM10 have different sources and are not equally harmful, with PM2.5 being demonstrably more dangerous.
- The Air (Prevention and Control of Pollution) Act, 1981 was enacted by India in response to the United Nations Conference on Human Environment held in Stockholm in 1972 — making India one of the first countries to legislate specifically on air quality.
- Under the Air Act, 1981, the Central Pollution Control Board (CPCB) sets National Ambient Air Quality Standards (NAAQS) while State Pollution Control Boards (SPCBs) implement and monitor compliance at the state level.
Statement 1 is correct — the Air Act, 1981 was enacted as a follow-up to India's commitment at the Stockholm Conference (1972), the first major UN environment conference, alongside the Water (Prevention and Control of Pollution) Act, 1974, and these two Acts form India's primary pollution control legislation predating the Environment Protection Act, 1986. Statement 2 is also correct — the CPCB prescribes National Ambient Air Quality Standards (NAAQS), the permissible concentration limits for key pollutants such as PM2.5, PM10, SO₂, NO₂, ozone, CO, and lead, while SPCBs handle implementation, monitoring, and enforcement at the state level, reflecting a classic Centre-State division of regulatory functions.
- List I: A. Sulphur Dioxide (SO₂) B. Ground-level Ozone (O₃) C. Carbon Monoxide (CO) D. Nitrogen Dioxide (NO₂)
- List II: 1. Formed by photochemical reactions between NOx and VOCs in sunlight — causes respiratory irritation and crop damage
- 2. Burning of fossil fuels in vehicles — binds to haemoglobin reducing oxygen transport, causing headaches and death at high concentrations
- 3. Combustion of sulphur-containing coal and petroleum in power plants and industries — causes acid rain and respiratory damage
- 4. Vehicle exhaust and power plants — causes respiratory problems and contributes to the formation of fine particulate matter and smog
Sulphur Dioxide (A-3) comes primarily from combustion of sulphur-rich coal in thermal power plants and industries, causing acid rain and severe respiratory and lung damage as a criteria pollutant under NAAQS. Ground-level Ozone (B-1) is a secondary pollutant formed when NOx and Volatile Organic Compounds react in sunlight, causing respiratory irritation, reduced lung function, and crop yield losses, distinct from beneficial stratospheric ozone. Carbon Monoxide (C-2) arises from incomplete combustion in vehicle engines and coal burning, binding to haemoglobin roughly 240 times more strongly than oxygen and reducing oxygen transport, which causes headache, dizziness, and death at high concentrations. Nitrogen Dioxide (D-4) comes from vehicle exhaust and thermal power stations, causing respiratory problems, contributing to smog, and acting as a precursor to ground-level ozone and fine PM.
- India's AQI was launched by the Central Pollution Control Board in 2014 under the Swachh Bharat Mission as a tool for public communication of air quality.
- India's AQI is calculated based on eight pollutants — PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃, and Pb (lead).
- An AQI value between 201 and 300 falls in the "Very Poor" category — causing respiratory illness on prolonged exposure.
- The AQI value reported for a location is the highest sub-index value among all measured pollutants — not an average.
Statement 1 is correct — India's National AQI was launched by the CPCB in April 2014 under the Swachh Bharat Mission as a single-number tool to translate complex air quality data into a publicly understandable index. Statement 2 is correct — India's AQI measures eight pollutants (PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃, and Pb), with a sub-index calculated for each. Statement 3 is incorrect since an AQI of 201–300 is classified as "Poor," not "Very Poor" — the categories run 0–50 Good, 51–100 Satisfactory, 101–200 Moderate, 201–300 Poor, 301–400 Very Poor, and 401–500 Severe. Statement 4 is correct, as the reported AQI is the maximum of all pollutant sub-indices rather than an average, ensuring the worst-performing pollutant determines the overall reading.
- Assertion (A): The Commission for Air Quality Management (CAQM) in the National Capital Region and Adjoining Areas, established in 2021, supersedes the powers of all State Pollution Control Boards and other bodies in the NCR for matters relating to air quality.
- Reason (R): The recurring air pollution crisis in the Delhi-NCR region — driven by stubble burning, vehicular emissions, construction dust, and industrial sources — required a single statutory authority with overriding powers to coordinate action across multiple states and Union Territories that share the airshed.
Assertion A is correct — the CAQM Act, 2021 established a statutory body whose directions override those of SPCBs, CPCB, and other authorities in the NCR and adjoining areas (Punjab, Haryana, Rajasthan, UP) on air quality matters, with orders carrying the force of law and criminal penalties for non-compliance. Reason R is correct and explains A, since the Delhi-NCR air crisis is a multi-state, multi-source problem spanning stubble burning, vehicular emissions, construction dust, and industrial units, cutting across state boundaries and requiring coordinated, overriding authority after the earlier fragmented structure of multiple SPCBs and CPCB repeatedly failed to produce coordinated action.
