Mumbai : Between January 29 and February 8, Mumbai ranked as the second most polluted city globally, according to Swiss air tracking index IQAir. Mumbai overtook Delhi as the most polluted city in India during this time. Despite falling in rank after February 2, Mumbai returned to second place on February 8 and reclaimed the top spot on February 13. The data used to monitor air quality in India is sourced from the Central Pollution Control Board (CPCB) and analyzed by IQAir, which works with UNEP and Greenpeace. Mumbai saw more Poor and Very Poor air quality days in November-January this winter than in the past three winters, according to CPCB data. Road and construction dust is responsible for over 71% of particulate matter in Mumbai’s air, with the remainder generated by factories, power plants, airports, and waste dumps. The reduction in wind speed along the west coast due to the La Nina effect has limited the dispersion of pollutants, exacerbating Mumbai’s air pollution problem.