New Delhi: After Delhi’s air quality improved on Sunday with an air quality index (AQI) of 181, it again slipped back to the 'poor' category on Monday with an index of 235, according to data at the Centre-run System of Air Quality and Weather Forecasting and Research (SAFAR).

What makes the air quality so poor?

According to the authorities, the change in direction of wind has brought about the change. The wind, currently, is flowing from stubble-burning areas in Punjab and Haryana.

Also, the Central Pollution Control Board (CPCB) said that increase in traffic on Monday heightened the pollution level in the city and the air quality fell.

In Delhi, the PM10 level was at 230, which shows the presence of particles with diameter less than 10mm in the air. Similarly, the PM2.5 level was at 101.

The air quality is expected to deteriorate further in the next two days, according to SAFAR. The authorities said, in the next three days, PM10 is expected to touch 264 and PM2.5 is expected to touch 111.

Here is the index for understanding the air quality

AQI between 0-50 — good

AQI between 51-100 — satisfactory

AQI between 101-200 — moderate

AQI between 201-300 — poor

AQI between 301-400 — very poor

AQI between 401-500 — severe

NASA satellites have picked-up several 'red spots' inside Delhi over the past couple of days, indicating that waste-burning in the open, despite a ban, are still rampant in the national capital.

Such incidents could worsen Delhi's already deteriorating air quality, and the EPCA has asked the Delhi Pollution Control Committee (DPCC) and other government agencies to step up their scrutiny.

Delhi's transport department has also begun a drive to confiscate, deregister and scrap diesel vehicles that are plying for over 15 years, in an attempt to limit vehicular emissions before the winter approaches.
In 2017, Delhi doctors declared a public health emergency after the capital was shrouded in heavy smog. 

Even the cricket Test match between India and Sri Lanka at the capital's Ferozshah Kotla was interrupted after few of the players fell sick and vomited as a result of the hazardous pollution levels.