Exactly how much does Diwali harm Delhi’s air?

News reports this year suggested that people are now more aware that fireworks increase air pollution in Delhi, and there were reports of reduced sales of fireworks. But with 22 million people, Diwali must go on. So that got me to thinking: just how bad does Diwali make our air?

To get to the bottom of it, I stationed our trusty Dylos DC1700 particle counter on my porch. I tracked (outdoor) air quality before, during, and after Diwali in Green Park, New Delhi. Here’s what I found:

Nerd note: I converted the Dylos 0.5 and 2.5 micron counts to approximate PM 2.5 ug/m3, which then gives us an AQI.

The left axis is PM2.5 and the colors represent the range of the AQI in ug/m3. Also plotted on the graph are some averages to put things in perspective.

Delhi winter air averages 220 micrograms/m3, but during the peak Diwali fireworks on November 11, our numbers spiked to almost 700 micrograms/m3! That’s 28 times the WHO 24-hour limit of 25 ug/m3.

By comparison, Beijing’s air is often criticized, but Delhi peaked at about 7 times the Beijing average.

I always look forward to Diwali, but I’ll be packing a pollution mask!