Centre for Science and Environment (CSE) has released its analysis of air quality data during the second phase of odd and even scheme – from April 15 to April 30. This shows that air pollution took a downward dip during the first 10 days of the scheme but registers a sudden spike from April 22 onwards. Further investigations and analysis of NASA satellite pictures has exposed massive crop fires in Punjab and Haryana that started around April 19 – which could be the reason behind the rise in pollution levels.