This Diwali, I bought myself air filters as a present. There was smoke hanging inside the house. Outside, the smog was reportedly the worst in 17 years. After procrastinating for many months,it was time to buy filters for the rooms. Apparently, I was not alone. As per the air filter company, they have been selling units in the hundreds per day last week, several times the usual demand. Why does it take a crisis to push us into taking steps to protect our own health?

Sadly, it takes a crisis to push government to act as well. The fact is this smog was entirely expected. Every year, air quality levels are toxic high between November and February, and Diwali represents one of the peaks. This is partly meteorology (which cannot be helped) and partly additional winter-specific emissions (which certainly can). Besides Diwali, the seasonal increase in emissions is due to post-harvest stubble burning by farmers in the region, and open fires for space heating when it gets cold.