While the concentration of particulate matter (PM10) is much more than the WHO-specified guidelines in the entire city, higher prevalence of sulphur dioxide (SO2) and nitrogen dioxide (NO2) in suburban wards such as S, T, N, R-South and K-East may have compounded the Covid crisis, states the study.
Wards in southern Mumbai, on the other hand, saw a relatively lower impact of pollutants, and therefore lower clustering of Covid cases too.
The study also noticed more Covid-related deaths in suburban wards where the population had prolonged higher exposure to NO2.
Mumbai’s suburbs with higher NO2 exposure due to industrial emissions and an increase in traffic in recent years are already at a higher risk of respiratory morbidity, say the researchers.
The researchers used ward-wise Covid data released by the BMC till August 15, 2020, and statistically correlated it with the data on pollutants. “While Mumbai has only 10 pollution monitoring stations, we used the Kriging interpolation technique (a popular method used in pollution modelling) to estimate the concentration of pollutants in neighbouring regions to get ward-wise data,” said Subhojit Shaw, co-author of the paper. The final edit of the study, authored by IIPS professor Aparajita Chattopadhyay and Shaw, was published in the American Geophysical Union’s journal GeoHealth on Monday.
The study also revealed that hotspots for Covid-19 and pollution exposure closely matched low-lying areas or wetlands, which face maximum waterlogging in monsoon. These include Kurla, Sion, Matunga, Mulund, Kalina, Ghatkopar, Juhu, Santacruz and Andheri, said Chattopadhyay. Along with NO2, the presence of drains significantly increases chances of Covid-19 fatalities, said Shaw.
V M Motghare, joint director, Maharashtra Pollution Control Board (who is not part of the study), though, said they did not come across high levels of NO2 during the lockdown.
“But studies have indicated that long-term exposure to air pollution affects human lungs’ efficiency and makes them vulnerable to respiratory diseases,” he said, adding MPCB is conducting an emission inventory study with NEERI and IIT-Bombay, which will help determine the contribution of each pollutant in 18 cities, including Mumbai.