New Delhi, Nov 23 (IANS): The air quality deteriorated to 'very poor' in the national capital and areas around it due to low wind speed and marginal effect of stubble burning in neighbouring states.

Several areas across Delhi also saw 'severe-plus' and 'severe' air quality due to high level of particle pollution, which remained over 10 times the safe limit.

The Air Quality Index (AQI) was 337 or very-poor against 273 or poor or Thursday. The AQI at Anand Vihar was 407 and of Mundaka was 432, both under 'severe' category.

PM2.5, or particles with diameter less than 2.5mm, is still the dominant pollutant. Despite dry and cool north-westerly winds, the air quality dropped to the average PM2.5 over 37 areas of Delhi recording 191 microgrammes per cubic meters, against 134 units on Thursday and 240 units on Wednesday.

"Air Quality Index will remain in very poor category on Saturday. A slight improvement is predicted later," said a forecast by System of Air Quality and Weather Forecasting And Research.

According to weather analysts, wind speed at present is slow allowing the pollutant to accumulate.

"Stubble fire will have a marginal impact," SAFAR said.

SAFAR has advised people to avoid outdoor physical activities.

"If asthmatic, keep relief medicine handy," the warning added.