According to a study conducted by the World Health Organisation, out of 1600 cities, Delhi has the worst air quality resulting in the significant number of deaths. Pollutants like noxious gases, toxic particles or biological molecules in the air are being introduced into the earth’s atmosphere at an exponential rate. There are two types of pollutants - primary and secondary. Primary pollutants are directly released in the air and include pollutants from industries. Secondary pollutants are not released but are formed in the air itself. When primary pollutants react with something in the air, it becomes the secondary pollutant. Both pollutants cause diseases, allergies and several other adverse health conditions. Some of the deathliest pollutants in Delhi air are carbon dioxide, sulphur oxides, carbon monoxide, ammonia and nitrogen oxides. Here are some of the effects of the air pollution.