PERSISTENT COLD weather conditions in comparison to last year and increasing rate of vehicular emissions have led to a rise in the number of ‘episodes’ of dipping air quality in December- January this year. While air quality deteriorates in winter, the period December to January 2016-17 has seen higher values as compared to the winter of 2015-16 in both Pune and Mumbai.
Scientists at System of Air Quality Forecasting and Research (SAFAR), which provides air quality forecast for 3 metropolitan cities Delhi, Mumbai and Pune, found that on almost all days from the period of December 24, 2016-January 6, 2017, the values were higher by more than 40- 50 points as compared to the same period in 2015-16.
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The Air Quality Index (AQI) is a health-related index based on air pollution for pollutants like NO2, PM 10 and PM 2.5. The Air Quality Index is based on air pollution with descriptor words ‘good’ for values of 0-100, moderate for 101-200 and poor for 201-300. In their analysis, Dr Gufran Beig, project director of SAFAR said that in Pune on December 30 last year, the air quality, according to the index, was poor and the value was pegged at 206. On December 30 in 2015, however, the value was 168 and here too, the air quality was moderate.
The analysis was done from December 24 last year till January 6 this year and the comparison was carried out to the values provided by the AQI in 2015-16. For instance on January 3 in 2016, the value was 144 – moderate air quality. The value had shot up to 193 – very near to the poor air quality range. On December 25 in 2015, the AQI showed 95 that shot up to 191 on December 25 in 2016.
In Mumbai, the levels had shot up from 248 registered on the AQI on January 3, 2016 to 315 on January 3, this year. On as many as six days the values were more than 310 indicating very poor air quality. The values were the highest on January 1 this year in Mumbai when the AQI registered 323 on the index indicating a severe dip in air quality.
Cooler temperatures prevent dispersal of pollutants and traps the emissions near ground as a result we can experience increased pollution levels. Again, PM 25 is the prominent pollutant and such higher concentrations need to be addressed on priority, Beig said.
The air quality trend follows a pattern— it is in the permissible range during monsoon, remains from ‘good ‘ to moderate during summer. The hard hit period, however, is winter when pollution levels peak and air quality dips to ‘poor’ category. Particles less than 2.5 microns are considered dangerous as these can penetrate into the lungs .
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