NEW DELHI: An analysis of a decade’s worth of air quality data shows that pollutants in Indian cities, including the national capital, follow sharply different seasonal patterns, underscoring the need to study each pollutant individually rather than rely on broad air quality trends.
A new public dashboard developed by research and advisory firm Envirocatalysts compiles daily air quality records from the Central Pollution Control Board since 2015, allowing users to track long-term trends across pollutants such as particulate matter, nitrogen dioxide, carbon monoxide and ozone.
“To truly reduce air pollution, we must track multiple pollutants across diverse timelines. The variations of each pollutant are fingerprints that reveal underlying sources and drivers, allowing us to move beyond broad data toward targeted action,” said Sunil Dahiya, founder and principal analyst at Envirocatalysts, explaining that understanding the complex seasonal patterns of each pollutant is essential to studying air pollution overall.
For example, a detailed analysis of PM2.5 levels in Delhi from 2015 onwards shows a trend of rising during the winter months, such as from October to February, with the level declining from March, following a seasonal pattern resulting not necessarily from a lower emission load but due to weather conditions dispersing pollutants faster and farther. A similar trend can be seen for PM10.
However, when a pollutant such as nitrogen dioxide is taken into account, a pattern is observed where higher concentrations are observed during the summer months compared to the winter.
Nitrogen dioxide shows relatively lower levels in the first few months of the year, similar to ozone.
Polluted ozone peaks in the summer months, reaching its peak in May.
Al-Dahiya said: “Examining patterns through the dashboard, which collects all data in one place, in easy-to-understand visualizations, attempts to bring complex data to all stakeholders to be able to better contribute to efforts to clean the air.”
As per Indian National Ambient Air Quality Standards and WHO guidelines, the Indian standard for PM2.5 is 60 µg/m3 and 40 µg/m3 per year. The WHO safe limit is 15 µg/m3 and 5 µg/m3.
In comparison, data analysis shows that Delhi recorded a monthly average of PM2.5 particles between 153-240 µg/m3 in January of 2015-2026. The level remained between 171-230 µg/m3 for the month of December. This decreased significantly in the middle of the year, as the monsoon approached.
The monthly average for July over the years has remained at around 30-66 µg/m3 and 25-59 µg/m3 for August.
For PM 10, the Indian standard is 100 µg/m3 and the annual level is 60 µg/m3; While the World Health Organization standard is 45 µg/m3, and 15 µg/m3.
Similar to PM2.5, PM10 also shows a dramatic rise in the winter months. The monthly average for January over the years has remained at around 240-446 µg/m3; In December, it remained at about 262-396 µg/m3.
In July and August, respectively, the monthly averages decreased to 75-148 µg/m3 and 56-173 µg/m3.
However, when pollutants such as ozone are taken into account, the monthly average remained relatively low for January, at between 31-55 µg/m3, compared to the WHO safe limit of 100 µg/m3. However, ozone sees a gradual rise in the summer months.
For April, the monthly average over the years remained at around 67-122 µg/m3, and for May, it remained around 67-101 µg/m3.
When another pollutant like nitrogen dioxide is taken into account, the monthly average for January remained at around 40-64 µg/m3, compared to the Indian standard of 80 µg/m3 and 40 µg/m3. The WHO standard is 25 µg/m3 and 10 µg/m3.
However, the monthly average increases to 47-108 µg/m3 for November over the years.
“It is clear that when you look at each pollutant individually, the trends over the months are different,” Al Dahiya said, adding that systematic reduction of air pollution can only happen when action is taken at the source and the emissions load is reduced.
He added, “We have to focus on this so that we do not depend on weather conditions to disperse pollutants and the situation does not worsen once favorable weather conditions turn unfavorable.”
PM2.5, CO, and NO2 are mostly emitted from combustion sources such as transportation, industry, and energy, while PM10 is mostly emitted from dust, construction, etc.
Ozone is formed as a reaction between nitrogen oxides and oxygen in the presence of sunlight, which leads to higher levels in the summer.
This article was generated from an automated news feed without any modifications to the text.
