Air pollution dropped by 79% in lockdown

Pollution levels in Delhi-NCR -- which had come down by around 79% during the initial phase of the lockdown, mainly owing to no industrial activity, reduced on-road traffic and a pause on construction activities -- is on an upswing again as the city gradually opens up, a study by Centre for Science and Environment (CSE) has found.

Of the six mega cities where PM 2.5 levels were studied during this period, Delhi saw the steepest rise of four to eight times, as compared to two to six times in other cities, the analysis shows.

CSE studied the PM 2.5 levels of six cities — Delhi, Mumbai, Kolkata, Chennai, Hyderabad and Bengaluru — during both the initial and last phases of the nationwide lockdown to check the spread of Covid-19.

According to the findings, while the PM 2.5 levels in other cities dropped by 45-88% in the initial lockdown phase and witnessed a pollution spike of 2-6 times on opening up, Delhi saw both the steepest drop and sharpest spike .

“In Delhi-NCR, one of the major factors that led to the drop in pollution was a 97% reduction in overall traffic and 91% reduction in trucks and commercial vehicles entering the capital during April, as compared to the prelockdown months of DecemberJanuary,” the study found.

It said, as compared to 84,399 heavy vehicles entering Delhi in January this year, only 7,942 plied during April, when the lockdown was in full effect.

PM 2.5 (ultrafine particles that can enter the lungs and blood stream) is the most prominent pollutant in Delhi-NCR as well as in other major cities across the country.

Between March 25 and May 18, when the nationwide lockdown was implemented without any major relaxations, the pollution levels in the national capital reduced drastically and remained in the “satisfactory” category for most of the time. After May 18, however, as lockdown rules were eased, the pollution graph started climbing again. From May 18 to June 5, the air quality index of Delhi has remained in the ‘moderate’ category. On Friday, the AQI levels was recorded as 111 in the moderate category, as per the CPCB.

The pollution levels were also kept in check because of the increased Western Disturbances that crossed Delhi during and after the lockdown period. Though not all Western Disturbances brought rain, the increased wind speeds helped blow away pollutants.

Sunita Narain, director general, CSE, said the analysis clearly shows that the nation needed an intervention at such a massive scale — where movement across the country was completely restricted, and all industrial activities stopped functioning — to clean our air and lungs.