Air quality in the capital was worse in July this year as compared to the average of the previous two years so far, with ozone being a prominent pollutant for the maximum number of days, data from the Central Pollution Control Board has revealed.
As per the data, the average air quality index (AQI) was around 136 so far this month — an increase of 32 from 2018, and 36 from 2017. The index is a measure of pollutants in the air and is calculated through their 24-hour average concentration value.
Air quality for July this year would fall under the ‘moderate’ category, which has an AQI range of 101-200.
Dr Gufran Beig, project director at the Indian Institute of Tropical Meteorology (IITM), Pune, said, “If the figures are true, then the number of rainy days last year were higher. High concentration of ozone in the air is usually witnessed in summer. If temperature increases, its production also increases.”
“We did a calculation last month and found that the number of days having ozone (as a pollutant) were higher this year,” he added.
There were 14 days having ozone as a prominent pollutant this month, as compared to 11 in July 2018 and just two the year before that. Ozone is formed naturally in the atmosphere as well as from other sources, including combustion of fossil fuels. Exposure to it can cause damage to human health.
A period of four days between July 11 and 14 witnessed a sudden dip in air quality, with the AQI ranging between 235 and 317. It’s possible that this was caused by a duststorm coming from Rajasthan during this period.
According to the data, PM 2.5 and PM 10 were among the major pollutants. Presence of carbon monoxide was also picked up by the monitoring stations between July 16 and 18, and July 26 and 29.