The air pollution level, which is gauged by the levels of respirable suspended particulate matter (RSPM), ozone (O3), nitrogen dioxide (NO2) and sulphur dioxide (SO2), has gone down by close to 70% now as compared to levels at the start of this year. The comparison has been done based on the data collected by the civic body's new Continuous Ambient Air Quality Monitoring Station (CAAQM) at Teen Hath Naka.

While the ceiling permissable limit of the RSPM is 100 grams per metric cube (g/m3), the first few months this year recorded an average of 200 to 326 g/m3. In the past few months, this pollutant concentration has dropped drastically to 81 g/m3 level. Meanwhile, the sulphur dioxide, nitrogen dioxide and ozone levels have also fallen from 37g/m3, 137g/m3 and 89g/m3 respectively to 8g/m3, 45g/m3 and 63 g/m3 respectively.

On the day when the city recieved its highest rainfall of 285.50mm on July 31, the rspm levels dropped to 65 grams per metric cube.

VidyadharWalavalkar, general secretary of NGO ParyavaranDakshataManch, said, "The heavy rains wash down the particulate matter in the air which is the major part of air pollution. Depending on their size, these pollutant particles can penetrate through the lung wall directly into the bloodstream, carrying toxins. The fresh rain water also dilutes or dissolves other gaseous pollutants and vehicular emissions like sulphur dioxide and nitrogen dioxide. Nature has its own way of sustaining itself. We have to ensure we don't disrupt it."

Meanwhile, the water pollution levels have also been brought down this monsoon. "There is a continuous flow of untreated waste water released into the creek, which combined with the waste dumped reduces the oxygen level in the creek, thus affecting the biodiversity. However, the heavy fresh monsoon showers have diluted this pollution level and increased the oxygen level in the waters," said R P Athalye, another city base environmentalist.

While these environmentalists peg this positive trend to the outstanding monsoons, which have diluted the concentration of pollution in the air and water, civic officials assert that their recent spree of green initiatives like the tree plantation drive, enviro-awareness campaigns and other green initiatives could be another factor for the decreasing pollution levels.

"The rains are one of the main reasons for the decrease in pollution levels in the air and the water bodies here. However, a small part of it could also be a result of the tree plantation campaign, cleanliness aware drive, drainage cleaning etc. ," said Manisha Pradhan, TMC's pollution control officer.