Air Quality
Air Quality – General Awareness Capsule for Railway Exams
1. What is “Air Quality”?
- Definition: Measure of how clean or polluted the air is, expressed through the Air Quality Index (AQI).
- AQI Range: 0–500 (lower is better).
- Primary Pollutants: PM2.5, PM10, NO₂, SO₂, CO, O₃, NH₃, Pb.
2. Global & Indian Air Quality Snapshot
| Statistic | Figure | Year | Source |
|---|---|---|---|
| WHO global deaths due to air pollution | 7 million/yr | 2022 | WHO |
| Indian deaths attributed to air pollution | 2.3 million/yr | 2021 | Lancet |
| Economic loss (% of GDP) – India | 1.36 % | 2019 | World Bank |
| World’s most polluted city (PM2.5) | Begusarai, Bihar (118 µg/m³ annual avg.) | 2023 | IQAir |
| India’s average PM2.5 | 58.1 µg/m³ (WHO limit = 5 µg/m³) | 2023 | CPCB |
3. Air Quality Index (India) – CPCB 6-category scale
| AQI Range | Category | Health Impact | Colour Code |
|---|---|---|---|
| 0–50 | Good | Minimal | Green |
| 51–100 | Satisfactory | Minor breathing discomfort | Light Green |
| 101–200 | Moderate | Respiratory symptoms | Yellow |
| 201–300 | Poor | Everyone may feel effects | Orange |
| 301–400 | Very Poor | Health alert | Red |
| 401–500 | Severe | Emergency | Maroon |
4. Key Dates & Milestones
| Date | Event |
|---|---|
| 5 June 1972 | First World Environment Day (Stockholm) |
| 4 Dec 1982 | Delhi switches to CNG public transport on Supreme Court order |
| 1997 | Launch of Bharat Stage (BS) emission norms |
| 1 Apr 2020 | Pan-India leap to BS-VI fuel (10 ppm sulphur) |
| 2019 | National Clean Air Programme (NCAP) launched – target 20-30 % PM2.5 reduction by 2024 |
| 2021 | Commission for Air Quality Management (CAQM) statutory status via ordinance |
| 2023 | WHO revises global AQ guidelines (PM2.5 annual limit 5 µg/m³) |
5. Institutions & Pollutants at a Glance
| Institution | HQ | Role |
|---|---|---|
| CPCB | Delhi | National AQ monitoring, AQI bulletin |
| SAFAR | Delhi + 4 metros | Real-time 1-km resolution forecast |
| CAQM | Delhi-NCR | Dust control, GRAP enforcement |
| TERI | Delhi | Research, source-apportionment |
| Pollutant | Major Source | Standard (µg/m³) India |
|---|---|---|
| PM2.5 | Diesel, coal, stubble | 40 (annual) |
| PM10 | Road dust, construction | 60 (annual) |
| NO₂ | Vehicles, power plants | 40 (annual) |
| O₃ | Secondary, sunlight reaction | 100 (8-h avg.) |
6. GRAP – Graded Response Action Plan (Delhi-NCR)
| Stage | AQI | Action Example |
|---|---|---|
| I | 201–300 | Stop garbage burning, mechanised sweeping |
| II | 301–400 | Ban diesel gensets, enhance parking fee |
| III | 401–500 | Odd-even traffic, shut brick kilns |
| IV | >500 | Entry ban on trucks, work-from-home 50 % |
7. Quick-Reference Tables
Table-1: Top-5 Polluted Indian Cities (Annual PM2.5, 2023)
| Rank | City | PM2.5 (µg/m³) |
|---|---|---|
| 1 | Begusarai | 118 |
| 2 | Guwahati | 105 |
| 3 | Delhi | 89 |
| 4 | Faridabad | 87 |
| 5 | Noida | 85 |
Table-2: Major Global Air Protocols
| Protocol | Year | Focus |
|---|---|---|
| Geneva Convention (LRTAP) | 1979 | Transboundary air pollution |
| Kyoto Protocol | 1997 | GHG reduction |
| Paris Agreement | 2015 | Climate & co-benefit for air quality |
8. One-liner Revision Bullets
- 1 µg = 0.001 mg – remember unit conversions.
- SAFAR = System of Air Quality & Weather Forecasting & Research – launched by MoES.
- EPCA = Environment Pollution (Prevention & Control) Authority – superseded by CAQM in 2021.
- Green War Room – Delhi Govt’s 24×7 air action control centre.
- BS-VI reduces NOx by 68 % and PM by 82 % vs BS-IV.
- World Air Quality Report 2023 published by IQAir, Swiss agency.
- Smog Tower at Connaught Place (Delhi) – 24 m high, capacity 1000 m³/s (experimental).
- COP-26 (2021) – India pledged net-zero by 2070, affecting long-term air quality.
- “Red Light On, Gaadi Off” campaign – Delhi traffic signal idling campaign.
- Parali (stubble) burning contributes ~40 % of Delhi’s winter PM2.5 peak.
15+ Railway-Style MCQs (with Answers)
Click to expand MCQs
-
Which Indian city recorded the highest annual PM2.5 level in 2023?
- A. Delhi
- B. Begusarai
- C. Mumbai
- D. Kolkata
Answer: B
-
The National Clean Air Programme (NCAP) aims to reduce PM2.5 and PM10 levels by __ % by 2024.
- A. 10–20
- B. 20–30
- C. 30–40
- D. 40–50
Answer: B
-
What is the permissible annual limit of PM2.5 under Indian NAAQS (µg/m³)?
- A. 5
- B. 10
- C. 40
- D. 60
Answer: C
-
Bharat Stage VI emission norms were implemented nationwide from
- A. 1 April 2017
- B. 1 April 2018
- C. 1 April 2020
- D. 1 April 2022
Answer: C
-
Which colour code represents “Severe” AQI category?
- A. Red
- B. Orange
- C. Maroon
- D. Purple
Answer: C
-
The Commission for Air Quality Management (CAQM) has statutory status under which ministry?
- A. MoEFCC
- B. MoHUA
- C. MoPNG
- D. MoRTH
Answer: A
-
SAFAR system is operated by
- A. CPCB
- B. IMD
- C. MoES
- D. NITI Aayog
Answer: C
-
Which pollutant is primarily responsible for ozone formation at ground level?
- A. SO₂
- B. NOx & VOCs
- C. CO
- D. NH₃
Answer: B
-
World Environment Day is celebrated every year on
- A. 5 June
- B. 22 April
- C. 2 October
- D. 16 September
Answer: A
-
Delhi’s first smog tower was inaugurated at
- A. India Gate
- B. Anand Vihar
- C. Connaught Place
- D. Punjabi Bagh
Answer: C
-
GRAP is enforced in which region?
- A. Mumbai-Pune
- B. Delhi-NCR
- C. Kolkata-Howrah
- D. Chennai-Bengaluru
Answer: B
-
Which fuel has the lowest sulphur content under BS-VI norms?
- A. 50 ppm
- B. 10 ppm
- C. 500 ppm
- D. 350 ppm
Answer: B
-
According to WHO 2021 report, what % of global air-pollution deaths occur in India?
- A. ~15 %
- B. ~25 %
- C. ~33 %
- D. ~50 %
Answer: C
-
Which of the following is NOT a criteria pollutant in India’s AQI?
- A. Pb
- B. Benzene
- C. NO₂
- D. CO
Answer: B
-
Stubble burning is most prevalent in which months?
- A. March–April
- B. June–July
- C. October–November
- D. December–January
Answer: C
-
The 2023 WHO guideline tightened the annual PM2.5 limit to
- A. 15 µg/m³
- B. 10 µg/m³
- C. 5 µg/m³
- D. 25 µg/m³
Answer: C
-
India’s first “Green War Room” was set up by
- A. Govt of Maharashtra
- B. Govt of Delhi
- C. Govt of UP
- D. Govt of Haryana
Answer: B
-
Which agency publishes the annual “World Air Quality Report”?
- A. UNEP
- B. IQAir
- C. NASA
- D. WHO
Answer: B
Last-Minute Cheat Sheet:
- AQI 0–50 → Green → Good
- PM2.5 Indian limit = 40 µg/m³; WHO 2023 limit = 5 µg/m³
- BS-VI = 10 ppm sulphur; BS-IV = 50 ppm
- NCAP target = 20–30 % reduction by 2024 (vs 2017 baseline)
- CAQM replaced EPCA in 2021
- SAFAR = MoES; CPCB = MoEFCC
- Stubble burning peak = Oct–Nov
- Smog tower height = 24 m (CP, Delhi)
All the best for your Railway exams – breathe easy, score high!
BETA
