Analyzing air pollution data from the US Consulate, Smart Air found that Kolkata’s air pollution rose 19% in 2018 compared to last year. This extra smog pushes Kolkata to an average of more than nine times the World Health Organization’s annual limit.
Kolkata started the year with January pollution above 2017. Kolkata air pollution was also worse from September through November.
With this bump up, Kolkata air pollution is inching closer to Delhi—currently the highest in air pollution among India’s major cities.
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.
How the rest of India fared in 2018
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.