Delhi’s pollution aggravated into the deep-red severe zone for the first time since November 17 on Friday, evidenced by another round of watery eyes, itchy throats and nausea, as residents of the city stared at another battle with an air emergency, even though farm fires in upwind states have started to dwindle.

The Capital clocked a 24-hour average air quality index (AQI) of 415 at 4pm on Friday, significantly worse than 390 a day ago, according to data from the Central Pollution Control Board (CPCB). It was Delhi’s ninth severe air day so far this month.

This rise has been wrought largely by local emissions, including vehicular emissions and dust from construction work, exacerbated by nearly still winds and dipping temperatures. Delhi clocked a minimum temperature of 9.4°C on Friday, only marginally higher than Thursday’s 9.2°C, and the second straight day the city’s mercury has stayed below 10°C.

READ | Delhi AQI in ‘severe’ category on Friday, unlikely to improve over weekend

Scientists with the India Meteorological Department (IMD) said the pollution is likely to give way marginally over the weekend, when winds are expected to get stronger and blow in from the east (instead of the northwest).

Further, Delhi may also get some rain on Monday, said IMD, owing to a western disturbance that will bring showers to Rajasthan and southern Haryana on Saturday and Sunday.

The latest downturn in Delhi’s air quality not only brought on the city a fresh round of health concerns, but also underscores the stickiness of the pollution problem. Pollution levels have been inching up for the past few days despite a steady downturn in the number of farm fires in Punjab, where most farmers have cleared out their paddy fields.

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Indeed, while Delhi’s air crossed into the ‘severe’ category after seven days, it’s been near that level for the past two days. Indeed, between November 17 and November 23, the Capital recorded AQIs of 319, 301, 348, 372, 395 and 390, respectively.

According to experts, the difference in health impact between the upper-range of ‘very poor’ and the bottom end of ‘severe’ is only statistical, and that air quality in either range poses significant health hazards for people of all ages.

The current prevailing levels can impact all age groups, with greater impact on vulnerable groups such as the elderly or schoolchildren, Dr GC Khilnani, chairman, PSRI Institute of Pulmonary, Critical Care and Sleep Medicine, said.

“This is largely because the elderly have compromised immunity and children’s lungs are more vulnerable to being impacted by these ultrafine pollutants. In the current air pollution scenario, stepping out in the early morning is particularly bad, with one advised to go out only using an N95 mask,” he said.

READ | Delhi’s air quality turns ‘severe’; AQI reading stands at 413

The deterioration prompted Delhi environment minister Gopal Rai to call for an emergency meeting, even as he directed agencies to enforce measures under the Graded Response Action Plan (Grap).

In fact, Delhi is on course to record its worst-ever average November air, according to CPCB records. So far this month, the city has registered an average AQI of 375, just a point behind November 2021 (376), which is the worst on record, since the index began capturing data in 2016.

Still, the city has been responsible for much of its own pollution for the past few days, especially with the drop in farm fires in surrounding states.

Punjab recorded 191 fires on Friday and Haryana 16, showed data from Indian Agricultural Research Institute (IARI). The count in the two northern states on Thursday was 205 fires and 23 fires, respectively. The number was 512 and 62 respectively on Wednesday. Punjab has clocked a decline in the number of farm fires for nine days now, show data.

Data from the Decision Support System (DSS), which estimates the sources of Delhi’s pollution in real-time, on Friday said farm fires likely only contributed to 2.2% of the city’s PM2.5 (an ultrafine pollutant) levels.

In comparison, the estimated contribution from vehicles in Delhi was 12.2%, with transboundary pollution from neighbouring Ghaziabad and Gautam Buddha Nagar pegged at 14.2% and 12.4%, respectively.

Experts pointed out that Delhi’s annual pollution saga was a problem of its own making, especially towards the end of November, December and January.

Sunil Dahiya, analyst at the Centre for Research on Energy and Clean Air (CREA) said there are no farm fires in upwind states in December and January.

“The temperature is dipping and has gone below 10°C, which makes the atmosphere more stable and less prone to allowing pollutants to disperse. Vehicles, which are Delhi’s biggest contributors of local pollution, are a source that has not been tackled and will continue to add emissions that can accumulate,” he said.

There may be some temporary, marginal relief in store from Monday, predicted experts.

“The wind direction was expected to switch to easterly on Friday, but this may happen towards Saturday night as the western disturbance approaches. This change in wind direction will raise temperatures again,” said IMD scientist Kuldeep Srivastava.

Warmer air allows pollutants to rise up and be dispersed.

Still, given that temperatures will only drop between now and January, and local emissions will remain unchanged, Delhi is unlikely to shrug off its smog blanket any time soon.