NEW DELHI: Delhi's air quality turned 'poor' on Wednesday -- the first time in over three months -- and is likely to deteriorate further due to unfavourable meteorological conditions and a spike in farm fires, according to government agencies.
The city recorded a 24-hour average air quality index (AQI) of 215, which falls in the 'poor' category. It was 178 on Tuesday.
An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.
This is the first time since June 29 -- when the AQI was 230 -- the air quality of the national capital has turned poor.
PM10 levels in Delhi-NCR stood at 234 microgram per cubic metre (µg/m3) at 6 pm, according to Central Pollution Control Board (CPCB) data. PM10 levels below 100 µg/m3 are considered safe in India.
PM10 is a particulate matter with a diameter of 10 micrometres and is inhalable into the lungs. These particles include dust, pollen and mold spores. The levels of PM2.5 -- finer particles which can even enter the bloodstream -- was 93 µg/m3. PM2.5 levels up to 60 µg/m3 are considered safe.
The Ministry of Earth Sciences' air quality monitor, SAFAR, said, 'PM2.5 is now becoming the lead pollutant instead of PM10 -- a characteristic of winters.' Surface winds were calm on Tuesday night. Similar conditions are likely for another two days. The AQI is expected to deteriorate further over the next three days, SAFAR said.
The cumulative fire count in Punjab, Haryana and the border regions was 336 on Tuesday.
'The boundary layer wind direction and speed are favourable for a slow transport (of pollutants) from external sources and local conditions are conducive for accumulation of pollutants in Delhi,' SAFAR said.
According to Punjab government's data, 169 farm fires were observed in the state on Tuesday. Overall, 1,692 'fire events' have occurred so far this season.
In Haryana, authorities have reported 526 farm fires so far this season.
Also, there is a marked dip in the minimum temperatures in Delhi. On Wednesday, it settled at 18.6 degrees Celsius, three notches below normal.
Low temperatures and stagnant winds help pollutants to accumulate near the ground, affecting the air quality.
The Delhi government launched a massive anti-air pollution campaign on Monday.
Chief Minister Arvind Kejriwal said he himself will review the situation on a daily basis. A 'war room' is being set up at the Delhi Secretariat to monitor the steps being taken to deal with the high levels of air pollution in winters.
Starting October 15, stricter measures to fight air pollution will also come into force in the national capital and its neighbouring areas as part of the Graded Response Action Plan, which was first implemented in Delhi-NCR in 2017.
These measures include increasing the frequency of bus and metro services, hiking parking fees and stopping the use of diesel generator sets when the air quality turns poor.
When the situation turns 'severe', GRAP recommends a closure of brick kilns, stone crushers and hot-mix plants, sprinkling of water, frequent mechanised cleaning of roads and maximising power generation from natural gas.
The measures to be followed in the 'emergency' situation include stopping the entry of trucks in Delhi, a ban on construction activities and introduction of the odd-even car-rationing scheme.