Across India, 70% of stations reported ‘severe’ PM2.5 readings

1. At a Glance

• What it is: The Hindu analysed data from all 634 Continuous Ambient Air Quality Monitoring Stations (CAAQMS) in the Central Pollution Control Board (CPCB) network. Nearly 70% of stations recorded peak PM2.5 in the 'severe' band (≥250 µg/m³) during the Deepavali window. [1]
• The pollution was not just a Delhi problem. Besides Delhi, at least seven States recorded peak PM2.5 levels during Deepavali. [1]
• It is also a data problem. Several stations stopped reporting, partly or fully, just after logging values close to 1,000 µg/m³ in the hour before. This raises the question of whether India's monitoring captures pollution at its worst. [1]
• UPSC relevance: The topic links air pollution (GS-III), the credibility of institutions and their data (GS-II/governance), and public health. Monitoring quality is a well-known weak spot in India's clean-air effort. [1][3]

2. Why in the News

• On 12 November 2026, The Hindu (Chennai edition, p. 11, by Pon Vasanth B.A.) published a station-level analysis of PM2.5 across the country for Deepavali 2026. [1]
• CPCB's clarification (Tuesday, 10 November 2026): CPCB said its particulate matter analysers are calibrated for a measurement range of up to 1,000 µg/m³. Its automated data validation system ignores values outside this range, so during "extreme episodes" such readings "may appear as a data gap". [1]
• Why the explanation is contested: Many stations went silent before they reached 1,000 µg/m³, while still reading values close to it in the previous hour. The article argues CPCB's statement does not fully explain these gaps. [1]

3. Background & Evolution

• CPCB runs a national CAAQMS network that feeds a central data portal. It also publishes daily air quality bulletins for the National Capital Region (NCR), archived at cpcb.nic.in/uploads/AQM/. [1][2]
• Earlier severe episodes: CPCB's NCR bulletins for the 2024–25 winter rated Delhi in the 'Severe' category with PM2.5 as the main pollutant. One December 2024 bulletin, for example, listed Delhi at Severe, AQI 409, PM2.5. [2]
• Long-running concern about monitoring: The Centre for Science and Environment's (CSE) State of India's Environment report calls monitoring an "Achilles' heel" in India's fight against air pollution. [3]
• Deepavali 2026 time windows used in the analysis: the pre-Deepavali window ran from 5 p.m. on 1 November to 5 a.m. on 5 November 2026, and this was compared with the Deepavali window. [1]

4. Core Static Facts

Item	Fact
Monitoring body	Central Pollution Control Board (CPCB) [1]
Network	634 CAAQMS in total [1]
Stations live during Deepavali 2026	Only 571 of 634, per CPCB's data portal [1]
'Severe' PM2.5 threshold used	≥250 µg/m³ [1]
Share of stations with severe peaks	~70% [1]
Upper limit of analyser calibration	1,000 µg/m³ [1]
How out-of-range values are handled	Ignored by automated validation, so they show up as a "data gap" [1]
States with peak PM2.5 apart from Delhi	At least 7 [1]
Pollutant measured	PM2.5: fine particulate matter of 2.5 µm diameter or less [1]
Bulletin series	CPCB daily AQ-NCR bulletins [2]

Uncited static reference (not found in this session's sources; check against the CPCB NAAQS 2009 notification and the AQI document): NAAQS PM2.5 limits are 60 µg/m³ (24-hour) and 40 µg/m³ (annual). The AQI has six categories, from Good to Severe, and the Severe band is AQI 401–500. CPCB's statutory basis is the Water Act, 1974 and the Air (Prevention and Control of Pollution) Act, 1981, under MoEFCC.

5. Multi-Dimensional Analysis

Environmental

• About 70% of stations hit severe peaks, which shows that festival-time episodes affect the whole country, not just the Indo-Gangetic Plain or Delhi-NCR. [1]
• Severe readings in at least seven States besides Delhi weaken the habit of treating this as only a Delhi problem. [1]

Scientific / Technological

• Instrument range limit: analysers calibrated only up to 1,000 µg/m³ cannot record the highest concentrations. [1]
• Validation design: an automated system that throws away out-of-range values turns real extreme readings into gaps. A better design would record them with a flag. [1]

Ethical / Governance

• Transparency: gaps that cluster at peak pollution weaken public trust and can make episode severity look lower than it was. [1]
• Network uptime: 63 stations, about 10%, were not live at all during the event. [1]
• Weak monitoring is a known structural problem in India's air quality governance. [3]

Administrative

• Uptime and maintenance at stations decide whether the data is usable. CPCB's portal itself showed only 571 stations live. [1][3]
• Emergency measures and enforcement depend on station data, so gaps at peak hours reduce how well they work. [1][2]

Social / Health

• Short, intense PM2.5 spikes put vulnerable groups at higher risk, including children, the elderly, and people with respiratory conditions. Data blackouts limit timely health warnings. [1]

6. Recent Developments (last 12–18 months)

• Winter 2024–25: CPCB NCR bulletins repeatedly rated Delhi 'Severe', with PM2.5 as the main pollutant. [2]
• CSE's State of India's Environment report: it named monitoring as the "Achilles' heel" of India's response to air pollution. [3]
• 1–5 November 2026: the analysis covered the pre-Deepavali and Deepavali windows. [1]
• 10 November 2026: CPCB attributed the data gaps to the 1,000 µg/m³ calibration limit and automated validation. [1]
• 12 November 2026: The Hindu reported severe peaks at ~70% of stations and challenged CPCB's explanation. [1]

7. Prelims Hooks

• CPCB's CAAQMS network has 634 stations. [1]
• Only 571 of 634 CAAQMS were live during Deepavali 2026. [1]
• About 70% of CAAQMS recorded peak PM2.5 in the 'severe' category during Deepavali 2026. [1]
• In the analysis, the 'severe' PM2.5 concentration band starts at 250 µg/m³. [1]
• CPCB's PM analysers are calibrated up to 1,000 µg/m³. [1]
• CPCB's automated data validation discards values above the calibrated range, and they show up as "data gaps". [1]
• At least seven States besides Delhi reported peak PM2.5 during Deepavali 2026. [1]
• The pre-Deepavali window ran from 5 p.m. on 1 November to 5 a.m. on 5 November 2026. [1]
• CAAQMS stands for Continuous Ambient Air Quality Monitoring Station. [1]
• CPCB publishes daily NCR air quality bulletins that name the main pollutant. [2]
• A December 2024 CPCB bulletin rated Delhi Severe (AQI 409), with PM2.5 as the main pollutant. [2]

8. Why a Silent Station Is Not a Clean Station

• When the worst hours go missing, every average built from that data comes out too low
• Many stations stopped reporting just after logging values close to 1,000 µg/m³ [1].
• The daily (24-hour) average is then worked out only from the hours that were recorded. Those are the cleaner hours.

• So the daily figure, and the AQI category that comes from it, can look better than the air people actually breathed.

• The data is missing at the very moment it matters most

• A gap at 3 p.m. on an ordinary day costs very little. A gap at the peak of Deepavali night removes the single most important reading of the year.

• These gaps came at pollution peaks, not at random times [1]. That is why they are a governance problem and not just a technical glitch.

• The 70% figure is probably an undercount, not an exaggeration

• Only 571 of 634 stations were live during the event [1]. We do not know how the 63 dead stations would have read.
• Stations that went silent near the top of the range also cannot show how high their peak really went [1].
• So the real picture is at least as bad as the headline, and possibly worse.

9. Is CPCB's Explanation Good Enough?

• The strongest case for CPCB
• An analyser is calibrated (tested and set to be accurate) only up to 1,000 µg/m³ [1]. A number above that limit cannot be trusted as an exact value.
• Removing readings you cannot trust is normal quality control. If CPCB published wrong numbers, people could attack those too.

• This part of CPCB's argument is fair, and an answer should say so.

• Where the explanation falls short

• It covers only readings above 1,000 µg/m³. But many stations went silent before they crossed that limit [1]. The calibration rule cannot explain those gaps.
• Even above the limit, the reading still tells us one true thing: the air was at least 1,000 µg/m³. Deleting the value throws away that fact.

• CPCB has not said why 63 stations were not live at all [1]. The calibration rule has nothing to do with that.

• A fair verdict

• CPCB is right that numbers beyond the calibrated range are not exact.
• It is wrong to let "not exact" turn into "not there". The public sees a blank and may read it as clean air.
• CSE has called monitoring the "Achilles' heel" (the weakest point) of India's fight against air pollution [3]. This episode is a live example of that warning.

10. Why the Clean Air Programme Cannot See a Festival Spike

• NCAP measures the wrong particle and the wrong time-scale for this problem
• The National Clean Air Programme (NCAP) aims to cut PM10 (coarser dust particles of 10 µm or less) by up to 40%, or meet the national standard of 60 µg/m³, by 2025-26 [4].

• The Deepavali story is about PM2.5 (finer particles) at short peaks [1]. A city can meet its yearly PM10 target and still choke for two nights a year.

• Money follows the PM10 number, so spending follows dust

• NCAP funds are released to cities based on how much they cut annual PM10 [4].
• CSE found that 64% of NCAP and 15th Finance Commission funds went to road dust control [5].

• CSE also warns that the PM10 focus has drawn attention away from PM2.5, which comes mainly from combustion (burning) [5]. Firecrackers are a combustion source, so festival smoke sits outside what the money is chasing.

• The most polluted places are not even spending what they get

• By May 2024, ₹10,566 crore had been released to 131 cities, and only about 64% of it had been used [5].
• Delhi and Noida had used less than 40% of their funds [5].
• So the gap is not only about missing money. The capacity to spend it is weak in exactly the cities that need it most.

11. What Should Change, and Who Should Do It

• CPCB should flag a high reading, not delete it
• Readings above 1,000 µg/m³ should appear on the portal marked as "above range". They should not become blanks [1].

• This keeps CPCB's quality concern and still tells the public the air was extremely bad.

• CPCB should publish a log of when each station was down and why

• 63 stations were offline and many more went silent at the peak [1].

• A public log of downtime would show whether the gaps follow a pattern. For example, it would show whether the gaps cluster at night or at the worst hours, or whether they are random breakdowns.

• MoEFCC should add a PM2.5 target to NCAP

• NCAP today judges cities only on PM10 [4].
• CSE's assessment argues the PM10 focus misses the more harmful PM2.5 from burning [5].

• A PM2.5 target, judged also on peak days and not just the yearly average, would make festival and winter spikes count when funds are released.

• State Pollution Control Boards should use the money already released before asking for more

• Delhi and Noida had used under 40% of their NCAP funds [5].
• Station upkeep is one direct place where unspent money could stop the next round of data gaps.

12. Anchors for Answers

• Data: About 70% of CAAQMS recorded 'severe' PM2.5 peaks (≥250 µg/m³) during Deepavali 2026. Only 571 of 634 stations were live [1]
• Data: Under NCAP, ₹10,566 crore was released to 131 cities, with about 64% used by May 2024. 64% of the money went to road dust control [5]
• Report/Committee: CSE, State of India's Environment, which calls monitoring the "Achilles' heel" of India's air pollution fight [3]. CSE's NCAP assessment says the PM10 focus misses PM2.5 [5]
• Scheme: National Clean Air Programme: up to a 40% cut in PM10 by 2025-26, with funds linked to each city's PM10 performance [4]

13. Mains Relevance

• GS-III: Conservation, environmental pollution and degradation; environmental impact assessment.
• GS-II: Government policies and interventions; transparency and accountability; statutory bodies (CPCB).
• GS-I (secondary): Urbanisation and its problems.
• Question stems: 1. "Air pollution in India is no longer a Delhi-centric problem." Examine this in light of recent station-level PM2.5 data. 2. Reliable, continuous data is the foundation of air quality governance. Critically evaluate the gaps in India's ambient air quality monitoring network and suggest reforms. 3. Discuss how festival-related emission spikes test the limits of India's air quality management framework, both regulatory and technological.

14. Related Topics to Study Next

• National Ambient Air Quality Standards (NAAQS), 2009: the legal limits that "severe" readings are measured against.
• National Air Quality Index (AQI): its categories and breakpoints; this is the source of the "severe" label.
• National Clean Air Programme (NCAP): the city-level reduction targets that depend on CAAQMS data.
• Graded Response Action Plan (GRAP) and the Commission for Air Quality Management (CAQM): emergency measures triggered by AQI levels in NCR.
• Air Act, 1981 and the CPCB/SPCB structure: the statutory basis of monitoring and enforcement.
• WHO Air Quality Guidelines, 2021: global benchmarks that are much stricter than NAAQS.
• Green crackers and Supreme Court firecracker orders: the regulatory response to Deepavali emissions.
• Stubble burning: an overlapping seasonal source of pollution in October–November.

15. NCERT Concepts to Revise

• Particulate matter (Geography): PM2.5 is the pollutant measured; knowing its size and health effects explains why severe peaks matter.
• Continuous Ambient Air Quality Monitoring Station (Geography): The article analyses data from these 634 real-time stations and their gaps during peak pollution.
• Central Pollution Control Board (Polity): CPCB runs the monitoring network and issued the contested explanation for the data gaps.
• National Air Quality Index (Geography): Source of the 'severe' category and its bands, which the article uses to classify readings.
• National Ambient Air Quality Standards (Geography): Legal PM2.5 limits that the severe readings are measured against.
• Air pollution (Economy): Broader background on sources and health costs of the pollution behind the Deepavali spikes.
• National Clean Air Programme (Geography): City-level pollution reduction targets depend on reliable station data like this.
• Graded Response Action Plan (Geography): Emergency measures in Delhi-NCR are triggered by air quality readings, which data gaps can distort.
• Commission for Air Quality Management (Geography): NCR-specific body that enforces emergency actions; the note warns against confusing its role with CPCB's.
• Air (Prevention and Control of Pollution) Act, 1981 (Geography): The law giving CPCB and State Boards their powers to monitor and control air pollution.
• Green crackers (Geography): The regulatory response to Deepavali firecracker emissions, which caused these spikes.
• Transparency (Polity): Data gaps at peak pollution hurt openness and public trust in official air quality reporting.

16. Common Errors / Trap Areas

• AQI value vs concentration: "Severe" on the AQI means an index value of 401–500 (unverified here). The PM2.5 concentration that maps to it is ≥250 µg/m³. Do not mix the two scales. [1]
• 634 vs 571: 634 is the total network, while 571 were live during Deepavali 2026. [1]
• The 1,000 µg/m³ figure is a calibration limit, not a standard. It is the analyser's measurement range, not any regulatory threshold. [1]
• CPCB vs CAQM vs SPCBs: CPCB runs the national CAAQMS network and the bulletins. CAQM is the NCR-specific commission. Do not swap their roles. [1][2]
• "Data gap" does not mean clean air. Under CPCB's own explanation, missing values may hide the worst readings. [1]