Cities high on toxic air this summer

NEW DELHI: The summer of 2022 one of the hottest in India’s recorded history witnessed widespread increase in the level of ozone gas at ground level, making the air in metro cities more toxic, says a latest analysis. 

Termed ‘ozone exceedance’, the phenomenon refers to above-normal ozone concentration at ground level.
According to latest air quality analysis by the Centre for Science and Environment (CSE), Delhi-NCR is followed by Mumbai, Kolkata, Hyderabad, Chennai and Bengaluru in the list of metros having higher levels of ozone exceedance.

Both Chennai and Bengaluru have longer durations of exceedance despite lower frequency compared to other metros. While Delhi-NCR recorded ozone exceedance on almost all days of this summer, Mumbai had 75 days of exceedance. The study warns that the issue can blow up as a major health crisis in the coming days.

“Even before we could control the problem of particulate pollution, the toxic threat of ground-level ozone is catching up with us. Despite the warning signs, this problem has not attracted adequate policy or public attention for mitigation and prevention. Inadequate monitoring, limited data and inappropriate methods of trend analysis have weakened the understanding of this growing toxic risk,” says Anumita Roychowdhury, executive director-research and advocacy, CSE.

The assessment has traced trends during summer (March-May) between 2019 to 2022 May (up to May 30). The analysis is based on publicly available granular real time data (15-minute averages) from the CPCB’s official online portal Central Control Room for Air Quality Management. 

New Delhi and south Delhi neighbourhoods were the worst affected. The data also showed hourly peak levels up by 23 per cent compared to lockdown times.  The 2020 State of Global Air report states that age-standardised rates of death attributable to ozone is among the highest in India. The seasonal eight-hour daily maximum concentrations have recorded one of the highest increases in India between 2010 and 2017.