Missing Diwali pollution data restored, PM2.5 levels hit 3,744 in Delhi

Most of the missing air quality data from Delhi Pollution Control Committee (DPCC) monitoring stations on Diwali night has been updated, revealing exceptionally high concentrations of particulate matter across the Capital, with PM2.5 levels touching 3,744 micrograms per cubic metre at Mundka.

However, gaps in official pollution records persisted on Tuesday, with some particulate matter readings still unavailable and data from Central Pollution Control Board (CPCB) monitoring stations remaining missing, raising questions over the completeness of the city's air quality monitoring exercise.

The revised figures showed that several locations experienced particulate pollution levels many times higher than the prescribed standards during the early hours of Monday, when widespread firecracker use had left Delhi enveloped in a thick toxic haze.

𝗣𝗼𝗹𝗹𝘂𝘁𝗶𝗼𝗻 𝗹𝗲𝘃𝗲𝗹𝘀 𝘀𝗼𝗮𝗿 𝗮𝗰𝗿𝗼𝘀𝘀 𝗗𝗲𝗹𝗵𝗶

At RK Puram, PM2.5 concentration surged to 2,389 micrograms per cubic metre at midnight, nearly 40 times the prescribed 24-hour standard of 60 micrograms per cubic metre.

PM10 concentration at the same station touched 2,881 micrograms per cubic metre, against the prescribed 24-hour standard of 100 micrograms per cubic metre.

At Anand Vihar, PM10 concentration peaked at 3,490 micrograms per cubic metre at 2 am on Monday, while PM2.5 levels reached 1,670 micrograms per cubic metre around the same time.

Ashok Vihar, where four hours of data had initially been missing, subsequently updated its readings. The revised figures showed PM10 concentration peaking at 3,425 micrograms per cubic metre at 2 am, while PM2.5 reached 2,589 micrograms per cubic metre.

At the Commonwealth Sports Complex monitoring station, which had earlier recorded nine hours of missing data, PM10 concentration peaked at 2,928 micrograms per cubic metre at 5 am. PM2.5 levels reached 2,471 micrograms per cubic metre at 4 am.

Dwarka Sector 8, which had initially reported eight hours of missing readings, showed only a one-hour gap around 8 am on Monday in the revised PM10 data.

The station recorded a peak PM10 concentration of 2,196 micrograms per cubic metre at midnight, while PM2.5 levels reached 1,996 micrograms per cubic metre at 6 am.

These were short-duration concentration readings, rather than 24-hour averages, but indicated the intensity of pollution during the peak exposure period.

𝗖𝗣𝗖𝗕 𝗱𝗮𝘁𝗮 𝗴𝗮𝗽𝘀 𝗽𝗲𝗿𝘀𝗶𝘀𝘁

Despite the restoration of most DPCC readings, some monitoring gaps remained unresolved on Tuesday.

At RK Puram, for instance, PM10 data for one hour on Diwali night was still unavailable.

Manoj Kumar, an analyst at the Centre for Research on Energy and Clean Air (CREA), said CPCB data for the night continued to remain unavailable.

An analysis of hourly PM2.5 readings from Delhi's 59 monitoring stations showed that only one station was not reporting data at 7 pm on Sunday.

However, the number of stations with missing readings increased steadily as the night progressed, reaching 36 by 1 am on Monday.

This meant that only 23 of the 59 stations were providing readings during one of the most polluted periods of the night.

Earlier records had shown that the Commonwealth Sports Complex, Jawaharlal Nehru Stadium, NSUT Jaffarpur and RK Puram stations each had nine hours of missing data.

Dwarka Sector 8, IIT Delhi, Jawaharlal Nehru University, Pusa (IITM), Talkatora Garden and Uttam Nagar had reported eight hours of missing readings each.

Although several of these gaps were subsequently filled, experts maintained that the delay in making critical pollution data available had undermined real-time assessment of the situation.

𝗣𝗠𝟮.𝟱 𝗰𝗿𝗼𝘀𝘀𝗲𝗱 𝟭,𝟬𝟬𝟬 𝗮𝘁 𝟮𝟬 𝘀𝘁𝗮𝘁𝗶𝗼𝗻𝘀

Sunil Dhaiya, founder and lead analyst at Envirocatalysts, said DPCC monitoring stations recorded PM2.5 concentrations exceeding 1,000 micrograms per cubic metre at 20 locations for a cumulative 126 hours during Diwali night.

The highest reading of 3,744 micrograms per cubic metre was recorded at Mundka, he said.

Dhaiya questioned why these extreme concentrations were not reflected in CPCB's published data.

"None of it shows in CPCB's data, which nearly halves the true peak. If the worst hours go missing, we misjudge both the health risk to people and whether our policies are working, so complete, uncapped and transparent data is non-negotiable," he said.

Experts stressed that missing or delayed readings during peak pollution episodes could affect assessments of actual exposure levels and the effectiveness of pollution-control measures.

Delhi recorded its most polluted Diwali in five years, with widespread violations of firecracker restrictions contributing to a sharp deterioration in air quality.

𝗗𝗼𝗰𝘁𝗼𝗿𝘀 𝘄𝗮𝗿𝗻 𝗼𝗳 𝗵𝗲𝗮𝗹𝘁𝗵 𝗿𝗶𝘀𝗸𝘀

Medical experts warned that exposure to extremely high concentrations of fine particulate matter could have serious consequences, particularly for children, older adults and people with existing respiratory illnesses.

Neurologist Rahul Chawla explained that PM2.5 particles are sufficiently small to bypass some of the body's natural filtration mechanisms and penetrate deep into the lungs.

"PM2.5 is a particulate matter whose size is much smaller than our nasal hair and that is why it cannot be filtered properly. Through our lungs, it reaches different parts of our body," he said.

Chawla said exposure to fine particulate pollution could trigger inflammatory responses and increase the risk of cardiovascular and neurological conditions.

"Multiple studies have come forward which show that exposure to PM2.5 increases chances of heart attack and stroke," he said.

He also highlighted research linking prolonged exposure to fine particulate matter with an increased risk of dementia and other neurological disorders.

Children, elderly people and individuals suffering from asthma or chronic obstructive pulmonary disease (COPD) were particularly vulnerable, he added.

Chawla further pointed to studies suggesting possible associations between prolonged particulate matter exposure during pregnancy and developmental risks in children.

𝗔𝗔𝗣 𝗮𝗹𝗹𝗲𝗴𝗲𝘀 𝗱𝗮𝘁𝗮 𝗳𝗿𝗮𝘂𝗱

The controversy over missing pollution readings also triggered political criticism.

On Monday, the opposition Aam Aadmi Party accused the Delhi government of "data fraud", alleging that air quality readings were being manipulated to understate the severity of pollution.

The allegations came after several monitoring stations stopped reporting data during the peak period of firecracker use on Diwali night.

While the subsequent restoration of DPCC readings provided a clearer picture of the extreme pollution levels, the continued absence of some official records raised concerns about the transparency of the monitoring system.

Experts reiterated that complete, timely and reliable air quality data was essential for issuing public health advisories, assessing exposure risks and evaluating the effectiveness of measures intended to control Delhi's recurring pollution crisis.