Rising mercury lowers pollution levels March Hotter Than Feb, But City Breathes Cleaner Air

The sudden rise in temperatures in the last few days is driving Mumbaikars up the wall, but the good news is that Mumbai is breathing cleaner air. The Maharashtra Pollution Control Board's (MPCB) statistics show that pollution levels have actually gone down since February. 

    Last month, suspended particulate matter (SPM) levels were three times higher than the ideal limit. While Mumbaikars are breathing air more polluted than ideal levels, it is considerably cleaner than February, thanks to the consistently high temperatures. "Anything above 100 micrograms of SPM and 80 micrograms of NOx in a cubic metre of air is bad for human health," said an MPCB official. 
    In the first few days of March, nitrogen oxide levels ranged between 117-184 micrograms per cubic meter. Though the ideal limit should be 80 micrograms per cubic meter, the current levels are much better than 230 units in the first half of February. 
    SPM levels in March ranged between 200-270 micrograms per cubic meter, an improvement over more than 300 units in February. SPM is a mix of solid and liquid particles, including dust, sand, smoke, lead, nickel and arsenic. It lodges in lung tissues and causes respiratory problems, aggravated asthma and acute respiratory symptoms including difficult or painful breathing, chronic bronchitis and decreased lung function. 
    Nitrogen oxides, on the other hand, include poisonous gases like nitrogen dioxide and nitrogen trioxide. The former is more dangerous. The reddish-brown toxic gas with a sharp, biting odour, makes children susceptible to respiratory diseases. 
    Dr Rakesh Kumar, of the National Environment Engineering Research Institute, said the heat has been instrumental in lowering pollution levels. "Temperatures have gone up and the strong winds helped dilute pollutants by blowing them away." 
    In February, pollution levels were high due to low temperatures. Normally, the air near the earth's surface is warmer than in the upper atmosphere. During inversion, however, there is cold air near the surface, which gets trapped under warmer air. "At such a time, hot and cold air don't mix easily in the upper atmosphere. Because of this, pollutants get trapped in the lower atmosphere," explained Dr Kumar. 
    Doctors however say pollution affects Mumbaikars through the year. "Pollution norms for vehicles may be in place, but their sheer numbers in Mumbai add to SPM levels," said Dr Neelam Rane, professor of physiology at DY Patil Medical College. "Also, there is always some construction, renovation or restoration work, which is an even greater source of pollution," she added.