Air pollution dipped up to 79% during lockdown in Delhi-NCR, rising again: Study

New Delhi: 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 pre-lockdown months of December-January,” the study found.

It said, as compared to 84,399 heavy vehicles entering Delhi in January this year, only 7,942 plied in the city 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 Central Pollution Control Board (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. “It tells us clearly what the key sources of air pollution are — emissions from vehicles and industry,” she said.

The study states that Delhi has an approximately 12.1 million registered vehicles, of which 4.6 million are private vehicles. Of these, only a fraction plied during the lockdown period. Also, visits to workplaces reduced by 60%, while retail and recreation activities reduced by 84%. Besides, activities in residential areas increased by 29%. Cycling and walking increased from 14% to 43%.

“The challenge lies in the fact that on opening up, we are likely to go back to the old habits. Today we are re-opening without any plan to keep the air clean. We need to set an agenda including prompt implementation of BS-VI for cleaner fuel, augmentation of public transport, create infrastructure and promote incentivised cycling and walking and introduction of cleaner battery-powered para-transit modes,” said Anumita Roychowdhury, executive director, research and advocacy and head of air pollution and clean transportation programme at CSE.

Brijmohan Das, atmospheric sciences researcher at IIT-Delhi, said that restrictions on human activities such as vehicular movement and industrial activities contribute a major chunk in the city’s pollution levels .

“This should be an eye opener for us. Without human presence, the environment heals itself and pollution levels reduce to satisfactory. Apart from the effects of lockdown, the high wind speed and rain in May and June has also helped the air quality,” Das said.