Delhi's air quality deteriorated to 'very poor' category on Thursday after showing signs of improvement in the last two days as the overall Air Quality Index (AQI) was recorded at 338 by the System of Air Quality Forecasting and Research (SAFAR).
The firefighting operations continued at the Bhalswa landfill site however, it's effect were visible on the air quality.
PM2.5 (presence of particles in the air with a diameter of less than 2.5 micrometres) was recorded at 169. PM10 level (presence of particles in the air with a diameter of less than 10 micrometres) in Delhi stood at 337, according to the data from SAFAR.
| Place | PM2.5 | PM10 |
| R K Puram | 240 | 195 |
| Dwarka | 105 | 209 |
| Anand Vihar | 322 | 471 |
| Gurgaon | 227 | N/A |
| Noida | 338 | 329 |
The Central Pollution Control Board (CPCB) recorded the city's overall AQI at 339 on Wednesday evening.
A Delhi Fire Service official said on Wednesday evening that firefighting was still underway at the garbage dump site.
"Fires at landfill sites do not come under control easily. Our operations are continuing for the past several days.
"Due to continuous discharge of methane gas from the landfill, fire erupts randomly," he said.
A fire has been raging at the massive dump site since October 20.
Delhi's environment minister held a multi-stakeholder review meet on Tuesday and directed all officers and agencies to be in "war mode" to combat air pollution.
Meanwhile, the Supreme Court on Tuesday set up a deadline for bursting firecrackers from 8 PM to 10 PM on Diwali and other festivals,
The court permitted the sale and manufacture of low emission "green" firecrackers countrywide.
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".
The permissible range or PM2.5 is 60 as per national standards and 25 by international standards.
The PM2.5, also called fine particulates, can be a matter of more serious health concern than PM10.
The slump in air quality is largely attributed to stubble-burning in neighbouring Punjab and Haryana and meteorological reasons such as low winds.