While air pollution in Delhi remains a major concern for its residents, the spike in ozone values has emerged a new threat for its people. On Thursday, green body Centre for Environment Science (CSE) has released a new study under the tagline - “Green areas More Vulnerable”.
Incidentally, the study is based on data collected at 31 monitoring stations of Central Pollution Control Board (CPCB).
In 2016, the CSE and other pollution monitoring institutions had studied on rising ozone at ground level while the outcome of study was higher levels of Aerosol Optical Depth (AOD) which may become the reason for damaging the vision.
In its latest findings showed that the ozone or O3 has showed up as the "dominant pollutant" along with particulate matter in the daily Air Quality Index (AQI) from February to May.
"During February-May, at least on 23 days, ozone has emerged as the dominant pollutant... These are the early signs of a dangerous trend," the study highlighted.
Although the study is "not comparative" as in 2017 data collected was very less -- four as compared to 31 in 2018, the geographical spread of ozone is cautioning, CSE experts said.
A highly reactive effluent, ozone is created as oxides of nitrogen (NOx) react with heat, sunlight and other volatile gases which are mostly product of vehicular pollution and other sources.
"Ozone is very harmful, especially for the patients with respiratory ailments, asthma and lung issues... chest pains, coughing, nausea, headaches are common symptoms," said Anumita Roychowdhury, executive director, research and advocacy and head of CSE,
It can also worsen heart disease. A study from Health Effect Institute in 2017 had shown that early deaths due to ozone have jumped by 148 per cent in India.
Although ozone is believed to form in highly polluted area, this study found that green regions like Dr. Karni Singh Shooting Range near Asola sanctuary were the most vulnerable.
In the shooting range, ozone levels exceeded the 8 hour average standards on 54 per cent of days in February, 87 per cent in March, 90 per cent in April, and 90 per cent in May, the study showed.
Densely-populated Patparganj, R.K. Puram, Nehru Nagar, industrial areas and low income areas of Najafgarh and Sonia Vihar, were also among the most vulnerable.
The study says that at such locations, ozone levels have exceeded the standards for more than 50 per cent of the days during the entire period of February to May. Besides, Gurugram in Haryana and lutyen's and Central Delhi are also affected by this rising threat, it pointed out.
Interestingly, Professor Krishna Kumar, School of Environmental Sciences, JNU, said atmospheric aerosols are known to affect the radiative balance: The relationship between the amount of energy reaching an object (or a portion of it) and the amount leaving it.
Explaining more on AOD load, professor Krishna said the microtops sun photometer measured AOD at discrete wavelengths between 340 and 1,020 nanometre with Full Width at Half Maximum (FWHM). "All calibrations were done by sending the instruments to Mauna loa, where it was calibrated using langley technique by the manufacturer, Solar light Company Inc., USA to the NIST (National Institute of Standards and Technology) traceable standards"
"To reach on conclusive observations, the AODs were measured over a long period of time (since December 2001 to May 2012), Among the 14, 651 point observations, AOD thickness was measured above the 0.6," said Kumar. (AOD thickness at 500 nm is measured with respect to the levels/load of Suspended Particulate Matter (SPM)).
While explaining the reasons of AOD escalation width in past 10 years, professor Kumar further said land use in NCR region, loose soil and a rapid growth in urbanisation in the Capital has led to such outcome. "The variations in land cover observed through satellite data, use of land periodically with respect to time have direct relation with the thickness of AOD," he added.