Smart Air analysed Mumbai’s PM2.5 air quality data provided by the US Consulate. What we found was that Mumbai’s PM2.5 levels increased 15% in 2018, giving much poorer air quality than the previous year. These higher air pollution levels push Mumbai’s annual PM2.5 average to more than seven times the World Health Organization’s annual limit of 10µg/m3.
Mumbai 2017 vs 2018 air pollution levels
Mumbai Monthly air quality
Mumbai’s PM2.5 levels started 2018 at higher levels than in 2017. Yet the largest difference in air quality over 2017 was the summer. In the summer of 2018, Mumbai’s air pollution, with July PM2.5 levels being three times higher than 2017. In 2017, Mumbai’s summer pollution levels were almost within the WHO annual limit of 10µg/m3, but not this year.
There was a slight respite for Mumbai in 2018 compared to the previous year. However, levels were still over 6 times the WHO limit and far from being healthy.
What does this mean about Mumbai’s air quality?
The graph above shows Mumbai’s air quality and PM2.5 levels are much worse during the winter months. Also, it’s evident that summer in 2018 was much more polluted than the 2017 summer. There are two periods which saw slightly lower PM2.5 levels: the months of May and September. These months, however, still had PM2.5 levels over 4 times the WHO limit.
Mumbai’s air quality levels compared to other cities in India
Mumbai’s air quality is now far worse than Hyderabad after this year’s worsening in PM2.5 levels. In 2017, Mumbai’s PM2.5 levels were similar to those of Hyderabad. The increase this year means Mumbai is now third in terms of worst air pollution among all of India’s major cities. Delhi — by far the most polluted city in India — still has pollution levels more than 30% higher than Mumbai.
What type of air pollution did we analyse?
This air quality analysis is for PM2.5 pollution: particles smaller than 2.5 microns in diameter. These types of particles are very considered the most dangerous since they 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.
What is PM2.5?
The data came from the US Consulate in Mumbai. It is open for researchers, although it does have its limitations. The data comes from only one pollution sensor in the city, which means a risk of the data not being representative to the whole of Mumbai. It’s highly possible that pollution levels vary between Mumbai’s different neighborhoods. If this was the case, then pollution levels in different neighborhoods could have drastically different pollution levels.
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. Doing this, we aim to lower the cost of breathing clean air for air breathers around the world.
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.