Delhi's air quality Wednesday oscillated between "poor" and "very poor" categories as authorities warned of severe deterioration of air quality even if "partial toxic crackers" are burned compared to last year.
The overall air quality index (AQI) was recorded at 281, which falls in the "poor" category, according the Central Pollution Control Board (CPCB) data.
The Centre-run System of Air Quality Forecasting and Research (SAFAR) recorded the overall air quality index at 319, which falls in "very poor" category.
Faridabad, Ghaziabad, Gurgaon, Noida and Greater Noida recorded "poor" quality air, according to the CPCB.
Eleven areas of Delhi recorded "very poor" air quality while 24 areas recorded "poor" air quality, according to the CPCB data.
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".
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The PM2.5 (particles in the air with a diameter of less than 2.5 micrometres) level was recorded at 143 while the PM10 (particles in the air with a diameter of less than 10 micrometres) was recorded at 281 in Delhi, according to the CPCB data.
The SAFAR has forecasted worse quality air for Wednesday evening and Thursday.
"The highest levels of PM10 and PM2.5 are expected between 11AM to 3AM on Wednesday and Thursday. Air Quality will be bad on Thursday and start to improve from Friday even if partial toxic crackers as compared to 2017 is burned," the government-run agency warned.
According to the SAFAR, both stubble burning in surrounding states of Delhi and firecrackers are causing deterioration of air quality in the national capital.
"The fire counts are seen to be very high but it is a combination of stubble burning and widespread firecrackers in that region and need not be confused with stubble only fire," the SAFAR said in a report Wednesday.
It also said that the combination of several rapidly changing weather parameters is playing a key role in controlling the air pollution at this time.
Delhi's air quality is expected to deteriorate to "severe plus emergency" category after Diwali, SAFAR said.
"Even if 50 per cent of the total load of toxic firecrackers as compared to Diwali 2017 is added, the prevailing weather conditions will aggravate the high smoke level and make air quality to persist in severe range for at least two days on November 8 and November 9," it said in a report.
SAFAR has also predicted that the PM10 concentration of Delhi is expected to reach 575 and PM2.5 to 378 on Thursday, recording the worst air quality of the year if fire crackers are burnt, it said.
The Indian Institute of Tropical Meteorology said the winds coming from north-westerly direction is bringing the influence of biomass burning to Delhi-NCR which may continue up to Thursday morning.
"The increase in PM2.5 concentration is due to change in wind direction, decrease in wind speeds and contribution from biomass burning," the IITM said.
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