Analyzing air quality data from the US Consulate, Smart Air found that Chennai’s air quality improved 9% in 2018 compared to last year. Despite the improvement, Chennai still averages over three times the World Health Organization’s annual limit.
Chennai air pollution by month
Breaking down the data by month, air quality started 2018 at worse levels. The rest of the months saw relatively similar levels, although April and October saw peaks of better air quality.
Chennai air pollution compared to Delhi
Compared to pollution leader Delhi, Chennai has some of the cleanest air among major cities in India, with air pollution averaging one-third that of Delhi. Although Chennai’s air quality is better than Delhi and Mumbai, Chennai’s PM2.5 exceeds the World Health Organization annual limit all months of the year.
The analysis is based on PM2.5 pollution, particles smaller than 2.5 microns in diameter that can penetrate deep into the lungs and even enter the bloodstream. Studies have shown that PM2.5 raises blood pressure, inflammation, and rates of heart attacks and strokes.
The US Consulate 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.
Protect yourself: Despite the harms of PM2.5, studies have found that wearing masks prevents physiological harm to the body, and placebo-controlled studies of air purifiers have found that removing particulate in the home has positive effects on blood pressure, inflammation, and immune response.
Smart Air provides empirically backed, no-nonsense purifiers and masks to help air-breathers protect themselves and their family. Smart Air is a certified B Corp founded to publicize the simple science behind air purifiers and masks, thereby lowering the cost of breathing clean air.
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.