How was Delhi’s air quality in 2021? Did Delhi’s air quality improve in 2021 compared to recent years? Delhi air quality has seen little improvement recently. Air pollution levels have hovered around 20x the World Health Organization’s (WHO) recommended limit for PM2.5 levels. Smart Air dove into the data to see if this trend has changed.
Results: Did Delhi’s Air Quality Improve in 2021?
After analyzing Delhi’s air quality data from the US Embassy, Smart Air found that air pollution increased 13% in 2021 compared to 2020. Despite this improvement, Delhi still averaged over 16 times the World Health Organization’s annual air quality limit, making it one of the most polluted cities in the world.
Delhi started 2021 on the wrong foot when air quality spiked in January. Most of Delhi’s reduction in air pollution came during the COVID-19 lockdown, with better air quality from March through September.
Delhi’s air pollution levels peak during winter with PM2.5 typically rising in October, and pollution levels remain high until March of the next year.

Progress or not, air quality data from 2021 shows that Delhi still takes the crown as the most polluted city among India’s major cities.
How We Measured Delhi Air Quality
The analysis is based on PM2.5 air pollution, particles smaller than 2.5 microns in diameter. These particles can penetrate deep into the lungs and even enter the bloodstream. Studies have found that PM2.5 raises blood pressure, inflammation, and rates of heart attacks and strokes.
The US Embassy data is open for researchers, although it is limited. It comes from only one pollution sensor in the city, and pollution can vary between neighborhoods.
How I Protect Myself
Despite the harms of PM2.5, studies have found that wearing masks prevents physiological harm to the body. Also using air purifiers in your home have been shown to have positive effects on blood pressure, inflammation, and immune response.
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