Delhi has witnessed significant ozone build-up this summer, which is adding to the public health risk, shows a latest analysis done by Delhi-based non-profit Centre for Science and Environment (CSE). Ground-level ozone is not directly emitted by any source. This is formed when oxides of nitrogen (NOX) and a range of volatile gases – primarily from vehicles and other sources – are exposed to each other in sunlight. Warm and stagnant air increases the formation of ozone. Ozone is extremely hazardous for human health. All neighbourhoods in Delhi – rich and poor – are at risk.
— source downtoearth.org.in