Particulate matter (PM) pollution is a global concern in developing countries which leads to a series of adverse health effects1,2. Delhi is one of the most polluted cities in the world3 with PM2.5 (PM with aerodynamic diameter less than 2.5 µm) levels as high as 1000 µg m-3. Organic matter is the dominant component in PM2.5, accounting for 40-50% of PM2.5 mass in Delhi4. However, little is known on the molecular distribution and sources of organic matter in Delhi.
