India's pollution monitors overwhelmed by toxic smog as Diwali haze engulfs Pakistan

India's air pollution monitors were overwhelmed this week by toxic smog so severe that concentrations exceeded their upper measurement limit, equivalent to 66 times the World Health Organization's recommended daily maximum, regulators said.

The admission comes after opposition politicians accused authorities of deliberately allowing gaps in official readings for several hours between Sunday night and Monday morning, just as pollution surged with a barrage of fireworks for Diwali, the Hindu festival of lights.

New Delhi is one of the world's most polluted capitals, where winter smog from vehicle emissions, farm fires and industry already chokes millions.

But the missing readings meant official data failed to capture the full extent of the pollution at its worst.

"The government which shuts down air quality monitoring stations on the night of Diwali, the government that does data fraud, how will you trust such a government?" opposition Aam Aadmi Party (AAP) Delhi president Saurabh Bharadwaj said in a video posted on X.

"If Diwali night's PM2.5 (toxic particulates) is not in the record, who will answer for that air?" senior Congress party lawmaker Ajay Maken said in a social media post.

The Central Pollution Control Board (CPCB) rejected accusations of deliberate under-reporting, saying the gaps reflected "differences in measurement of pollutant concentration" rather than an attempt to conceal pollution.

'Extreme episodes'

Particulate matter analysers, installed when the National Air Quality Index (NAQI) was introduced in 2015, were calibrated to measure concentrations of up to 1,000 micrograms per cubic metre.

The WHO recommends a daily maximum of 15 micrograms per cubic metre for PM2.5, fine particles small enough to penetrate deep into the lungs and linked to cancer.

"The designed system of automated data validation treats hourly readings beyond the calibrated range as outside range, and such readings are not used in the computation," the Central Pollution Control Board (CPCB) said in a statement late on Tuesday.

"During extreme episodes, which are occasional like Diwali firecracker bursting, this may appear as a data gap at the particular station concerned", it added.

Although choking clouds filled the streets early on Monday, the scale of the pollution was only captured when monitors resumed reporting, around eight hours after the fireworks peaked.

Readings then hit 879 micrograms per cubic metre in the Mandir Marg locality, according to monitoring organisation IQAir, which cited data from a city government station. That is more than 58 times the WHO daily limits.

"There is one thing the people of Delhi can be certain of: the fact that the data has gone missing doesn't mean the pollution has disappeared too," Congress party lawmaker Pawan Khera added.

"The poisonous smoke we have been inhaling... will continue to choke our lungs, threaten our lives and shorten our life expectancy."

Pakistan blames India's Diwali fireworks for Lahore's toxic air

Meanwhile, Pakistan blamed poor air quality this week on pollution drifting from neighbouring India.

The northern Pakistani city of Lahore topped Swiss group IQAir's ranking of the world's most polluted major cities for a second day on Tuesday, with an AQI of 263, categorised as "very unhealthy".

The city's concentration of PM2.5, harmful airborne particles small enough to penetrate deep into the lungs, was 37.2 times above the WHO's annual guideline, IQAir said.

Pakistani Punjab's Environment Protection Minister Marriyum Aurangzeb said pollutants had been carried into the region by light winds and air drifting from India in the aftermath of Diwali.

IQAir ranked Delhi the world's second-most polluted major city on Tuesday, with an AQI of 188. Indian government data showed that firecrackers were responsible for nearly 55 percent of the PM2.5 in the Indian capital a day earlier.

Vehicle emissions, construction dust and smoke from crop-waste burning are also major contributors to winter pollution on both sides of the border.

TRT World and Agencies — TRT World and Agencies