MUMBAI, Jan. 20 -- The city saw a sharp spike in air pollution levels over 48 hours, with the air quality index (AQI) rising from 89 (satisfactory) on Friday to 167 (moderate) on Saturday and 210 (poor) on Sunday, according to the System of Air Quality Weather Forecasting and Research (SAFAR) for PM2.5 (particulate matter of the size 2.5 microns that can easily enter the lungs and cause health ailments). Researchers said the spike was a result of temperature fluctuation....