The concentration of suspended particulates PM 2.5 and PM 10 were recorded nearly three times above the prescribed standards even as air quality remained in the 'very poor' category for the sixth straight day.

After rising through the day, PM 2.5 settled at 160 micrograms per cubic metre (ug/m3) and PM 10 at 277 ug/m3 around 7 pm. The corresponding 24-hour safe averages are 60 and 100.

Dipankar Saha, air lab chief of the Central Pollution Control Board (CPCB), attributed the rise to the influx of moisture due to the change in wind movement to south-westerly and fall in speed of local winds.

The presence of strong local winds helps in flushing out particulates while the presence of moisture traps pollutants near the surface.

"Cloud formation in the northeast and southern India is hindering the flow of wind from the north and northwest. As a result, even winter is not settling in."

"On the other hand, there is an intrusion of humidity from east and southeast. It is likely to cause a spike in air pollutants and also bring down visibility," Saha said.

The CPCB recorded the city's AQI as 334, marginally higher than yesterday's 307.

The AQI takes into account levels of suspended particulate matter and gases such as nitrogen dioxide and ground-level Ozone.

A "very poor" AQI essentially means that people may suffer from respiratory illness on prolonged exposure to such air.

On further dip in air quality, the AQI will turn "severe".