The nationwide ''Janata Curfew'' followed by the 21-day lockdown to combat the coronavirus outbreak have led to a significant reduction in pollution in the country with 91 cities recording air quality in the ''good'' and ''satisfactory'' category on March 29, a Central Pollution Control Board report has stated.
Travel restrictions and closure of industries have helped reduce the pollution level, it said.
"The major sectors contributing to air pollution are transport, industries, power plants, construction activities, biomass burning, road dust resuspension and residential activities. In addition, certain activities such as operation of DG sets, restaurant, landfill fires, etc. also contribute to air pollution," the pollution watchdog said.
"As a result of stringent travel restrictions and shutting down of non-essential activities including those of air polluting sectors, air quality improvement has been noted in many towns and cities across the nation," it added.
According to the report, on March 21 (a day before the Janata Curfew) a total of 54 cities recorded ''good'' and ''satisfactory'' air quality while on March 29 as many as 91 cities recorded minimal pollution.
India is currently under the biggest lockdown with around 130 crore people asked to stay home in view of the coronavirus outbreak, which has claimed 50 lives and infected over 1,900 people in the country.
Since the lockdown was imposed, the air quality all around the country has shown drastic improvement due to eradication of local pollutants generated due to construction activities and vehicular traffic among others.
The CPCB has released a report on the impact of the ''Janata Curfew'' and lockdown on the air quality.
Out of the 91 cities that showed minimal pollution, as many as 30 cities recorded ''good'' air quality while 61 cities recorded ''satisfactory'' air quality, the report showed.
Moreover, the number of cities recording poor to severe air pollution also came down from nine (March 21) to 0 (March 29), the report said.
An AQI between 0-50 is considered good, 51-100 satisfactory, 101-200 moderate, 201-300 poor, 301-400 very poor and 401-500 severe. The Air Quality Index is an assessment of the air quality by taking into account different factors. The lower the AQI the better the air is considered to be.
Delhi which battles high levels of pollution almost through the year also showed significant improvement.
On the day of the ''Janata Curfew'', as a result of a combination of reduced vehicles on the road, functioning of only essential commercial units and prevailing weather conditions, a significant reduction was noted for PM10 and NOx (nitrogen oxide) levels, the report said.
On March 21, the AQI was ''Moderate'' in Delhi which gradually improved from higher to lower end of the category.
"Overall, up to 44 per cent reduction in PM10 levels was observed in Delhi during March 22-23, compared to the previous day. The PM2.5 reduction was though 8 per cent on the curfew day but declined to 34 per cent the next day owing to negligible combustion activities," the report said.
The report said the air pollution reduction trend in NCR towns was relatively less pronounced compared to NCT of Delhi.
"While, reduction in PM10 levels were observed on March 22, 2020 in all neighbouring towns except Gurgaon, PM2.5 levels remained high, showing only slight reduction in Noida (6 per cent) and Ghaziabad (9 per cent). This can be attributed to localized combustion activities in NCR towns.
"Similarly, while significant reduction in NOx levels was observed in Noida (55 per cent), Ghaziabad (51 per cent), the same was not noted in Gurugram (4 per cent) and Faridabad, where NOx emissions were found higher during early hours of curfew signifying higher vehicular movement during that period," it said.
In other cities, the CPCB said the improvement in air quality of 85 cities was noted as most of the vehicles remained off road and non-essential industrial units closed during Janta Curfew and national wide lockdown.
The report further said that most of the million plus population cities, which have high population density and substantial share of emissions from the transport sector, showed improvement in air quality levels.
Indo gangetic cities showed significant improvement in AQI values with levels moving from higher to lower end of the category and 17 cities moving in the ''satisfactory'' category and seven cities in ''good'' category.
The AQI value in coastal areas was slightly improved though not as significantly as noted for Indo gangetic plains, the report said.
"On the day of the curfew, Chennai and Mumbai remained in the ''satisfactory'' category, however a slight increase in AQI value was noted in Chennai on the next day, possibly due to local contribution.
Higher AQI value was seen in Kanpur with PM2.5 as a prominent pollutant, likely emanating from local combustion sources, the report said.
However, the report said the positive impact on air quality was not observed significantly in industrial cities.
"High AQI value was noted in Vapi, Ratlam (Sulphur di-oxide as a prominent pollutant), Satna, Singrauli and Chandrapur seemingly due emissions from industrial areas.
"Overall, Janta Curfew resulted in general improvement in air quality across the country with the quantum of improvement being varied based on local contribution sources, though regional contribution was largely absent," it said.