Which cities in India have the best and worst air pollution? I analyzed data from the World Health Organization’s database of annual particulate pollution (PM2.5) averages for 122 cities. Here’s what I found.
Agra Through Mumbai
122 cities is too much for one graph, so I broke it in half. Here’s A through M from highest to lowest.
Here’s that same list in alphabetical order.
Nagaon Through Warangal
Here’s N through Z from highest to lowest.
And here’s that same list in alphabetical order.
Takeaway 1: It helps to be later in the alphabet
For some unknown reason (regional linguistic differences?), you’re better off on average if you’re in an N-Z city (48 micrograms) rather than an A-M city (66 micrograms).
Takeaway 2: Only one city is under the WHO annual limit
The World Health Organization’s annual limit is 10 micrograms/m3. Only one city came in under that limit—Tezpur, Assam.
Maybe 10 micrograms is a ridiculous, unattainable limit? It’s true that my university’s city, Chicago, is above that limit (12 micrograms), although New York City is just below it (9 micrograms). Many major developed cities are around 10 micrograms.
Takeaway 3: Seven cities are under the looser WHO 24-hour limit
If the 10 microgram limit is too strict, we can try out the looser 24-hour limit of 25 micrograms. Based on that limit, seven cities on the top 10 list make the cut. That’s a meager 6% of cities under this looser limit.
India’s Top 10
India’s top 10 cities according to this database are:
- Tezpur (6 micrograms)
- Pathanamthitta (12)
- Hassan (19)
- Chitoor (21)
- Kollam (22)
- Puducherry (22)
- Bongaigaon (24)
- Madurai (26)
- Warangal (26)
- Alappuzha (27)
India’s Bottom 10
The cities with the worst air according to this database are:
- Gwalior (176 micrograms)
- Allahabad (170)
- Patna (149)
- Raipur (144)
- Delhi (122)
- Ludhiana (122)
- Kanpur (115)
- Khanna (114)
- Firozabad (113)
- Lucknow (113)
Now, this data isn’t perfect. For one, it’s from 2012, so it’s a bit old.
Second, some cities don’t measure PM2.5, so the WHO infers it from the larger PM10 particles (what’s the difference?). I’ve discovered that the WHO database vastly underestimates pollution levels in Beijing compared to my analysis of local data.
To some extent, the exact top and bottom cities are arbitrary. Different articles use different data sources and will come up with different sets of cities. But the bigger picture of air quality across India holds up regardless of the dataset.
P.S. What kind of an answer would this be if there weren’t some solutions in it? After coughing through Beijing’s smog for years, I’ve combed through the data, done my own tests, and found several cheap ways to protect my lungs:
芝加哥大学行为科学系的助理教授; Smart Air创始书呆子。