Missing Diwali readings raise concerns over pollution data transparency.
Data gaps undermine public health responses and government accountability.
India needs transparent, reliable and complete pollution monitoring records.
At 2 am after Diwali, Mundka in Delhi recorded an hourly PM 2.5 concentration of 3,744 micrograms per cubic metre, initially missing from Central Pollution Control Board (CPCB) records. It was over 15 times the concentration at 7 pm earlier that evening. For context, the WHO guideline value for a 24 hour average PM2.5 concentration is 15 micrograms per cubic metre.
That gap in public record affects the evidence by which citizens judge the government’s response to pollution. Incomplete readings obscure the scale of exposure and weaken scrutiny of official claims of improvement. Public trust on public institutions depends on availability of strong public data.
Private app readings labelled “3000 AQI” had circulated widely, although differing scales and averaging periods complicate comparisons with official figures. Yet the government’s own subsequently released measurements documented extreme pollution. Fine particulate matter causes cardiovascular and respiratory disease, both generally and specifically in Delhi’s case. People had already breathed the air by the time the fuller (but still incomplete) official picture emerged.
Crisis Beyond Delhi’s Borders
The crisis extended far beyond Delhi. On November 9, 99 of the 100 cities topping one private platform’s live pollution ranking were Indian. This was a snapshot of the platform’s monitored cities, with the limitations such rankings carry. It still offered a stark and grim picture of the pollution enveloping and slowly choking the country.
Even before this, it’s not like Delhi’s pollution monitoring was seen as gold standard. Reporting documented water spraying near monitors and malfunctioning displays, while the opposition has alleged that spraying specifically targeted instruments to lower readings. These concerns make the missing Diwali readings a further test of public confidence.
Stations stopped publishing particulate readings as concentrations approached 800–1000 micrograms per cubic metre. The Delhi Pollution Control Committee (DPCC) later released some missing readings, but gaps remained at stations run by CPCB and the Indian Institute of Tropical Meteorology. DPCC also revised readings at Jahangirpuri. An official attributed the gaps to a technical glitch.
Missing Data Understates Exposure
The credibility of an environmental monitoring system is tested when pollution becomes extraordinary. If some of the highest readings of the year are disproportionately lost at the most critical times, averages calculated from the remaining observations can understate exposure.
A blank can therefore change the public account of an emergency. The resulting number may look reassuringly precise while concealing how much information is absent.
The larger consequences of lost or missing data are important but the immediate consequences are critical. For Delhi's estimated 3,00,000 homeless people, many of whom sleep outdoors with no option to retreat indoors, reliable pollution data should be a trigger for urgent public health interventions and emergency protective measures, far beyond a matter of public information.
Other residents too need timely information to judge whether to step outdoors, change travel plans or seek protection at work. Outdoor workers often have little choice about exposure.
The harm can outlast the night, and later releases cannot restore that opportunity beyond repairing the historical record. Without transparent corrections, incomplete figures can travel into official briefings, research and claims of policy success.
A government could appear to have reduced pollution in part because its monitoring system failed to capture the worst hours.
India is, of course, not alien to public data and statistics not being accorded the respect they deserve; public information being indefinitely paused is sadly common.
The census scheduled for 2021 was postponed during the pandemic - the government subsequently announced Census 2027. This prolonged interval of over half a decade leaves planning dependent on an ageing population count, supplemented by estimates, as settlements grow and people migrate and the world moves on.
National reports on crime and suicides for 2023 were still awaiting publication in August 2025. Parliament received substantially the same explanation about final stage validation in March and August. Such delays also held up information about deaths among farmers and agricultural labourers. The 2023 suicide report was subsequently made available.
Examples are many. In 2019, the government withheld the 2017-18 consumer expenditure survey, citing data quality concerns. Newer surveys have since been published; the missing round still left a gap in evidence about household living standards. Each episode of public data being ignored has its own explanation but each one deserves scrutiny proportionate to its public consequences.
Public data allow citizens to judge whether their government is protecting them, and public trust depends on people being able to test what institutions say. Citizens fund these systems and directly bear the consequences of decisions based on them.
When data goes publicly missing, explanations are vague and/or publication unpredictable, especially at the most critical junctures, suspicion naturally grows.
In case of Delhi pollution, where official/ government AQI figures are already facing scrutiny for understating actual figures of exposure, disappearance of monitoring data when pollution peaks risks compromising the government's ability to recognise and respond to a public health emergency.
A Capital’s Credibility Test
Delhi gives this failure national significance too -- the capital houses the biggest national institutions and represents India before the world. Its residents’ struggle for breathable air should offend any reasonable expectation of competent government.
Every Indian has a stake in whether these institutions, especially those in Delhi but also in those other 98 cities, respond honestly to an emergency visible on their doorstep.
Beijing famously demonstrates that sustained improvement is possible. Its fine particulate pollution fell by 35% between 2013 and 2017, following measures addressing coal, energy infrastructure and vehicle emissions. The comparison should raise expectations of Delhi’s government and strengthen demands for measurable results.
Delhi’s pollution boards should publish a complete record, explain exclusions, correct affected bulletins and commission an independent technical audit.
Dashboards should display timestamps and data coverage prominently. Institutions must demonstrate accountability through records researchers (and the public) can inspect. A public forced to endure dangerous air is entitled at least to a complete account of it.
Rishiraj Bhagawati is a public health policy researcher based out of Bengaluru.
(Views expressed are personal)
