According to the State of Global Air Report 2022, Calcutta is the second-most polluted city in the world in terms of air pollution and the presence of PM 2.5 in the air; Delhi grabbed the top slot. Since the study calculates pollution on the basis of a population-weighted average, it cannot be argued that it is the density of population that earns Indian cities — Mumbai made it to the top 20 along with Delhi and Calcutta — this dishonour. It could be asked, though, why Calcutta, which lags far behind Mumbai and Delhi as far as industry — a chief source of air pollution — is concerned, has such poor air quality. But the challenges are multifold. Whereas previously vehicular pollution shouldered most of the blame for Calcutta’s — indeed Bengal’s — toxic air, a study by the Bose Institute, conducted between 2004 and 2018, found that 20 to 25 per cent of the overall PM 2.5 in Calcutta comes from Uttar Pradesh, Bihar, Jharkhand, Assam and Meghalaya as well as neighbouring countries like Bangladesh and Nepal. Similarly with Delhi, around 64 per cent of its winter pollution load comes from outside the capital’s boundaries. Collective action, therefore, is the only way to mitigate the health and economic risks of transboundary pollution. This includes stronger federal and international cooperation, collecting and sharing data, and enhanced research and public awareness.

Ultrafine PM 2.5 was responsible for 1.85 lakh premature deaths in Calcutta between 2011-19 according to the Health Effects Institute, which brought out the SGAR 2022. While they may not be the primary cause of air pollution, the 92 lakh out-of-date vehicles plying in the state cannot be ignored. It is shameful that the state government has failed to comply with repeated legal and institutional directives regarding phasing these out. The Intergovernmental Panel on Climate Change has, hearteningly, lauded Calcutta as one of the nine cities globally with the most robust public transport system with as many as 12 different modes of travelling that can bring down pollution significantly. There is thus a need to weed out the challenges to this network. For instance, at a time when the world is rediscovering the green utility of trams, Calcutta is witnessing a systematic effort to discontinue this vital cog in the wheel of public transport. Waterways remain underutilised. The SGAR 2022 is a wake-up call to the city fathers to smell the toxic air.