Air quality 'severe' in Delhi

Pollution levels continued to be in the 'severe' category on Wednesday as a blanket of smog wrapped Delhi. According to the Central Pollution Control Board, the air quantity index was 416 at 11 am.

On Tuesday, the overall air quality index was 414 at 8 pm, worse than Monday's AQI of 397, according to the CPCB. An AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor', and 401-500 'severe'. Above 500 is the 'severe-plus emergency' category.

The AQI takes into account five chief pollutants -- particulate matter with a diameter less than 10 micrometers (PM10), PM2.5, ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). The higher the AQI value, the greater the level of air pollution and the greater the health concern.