Delhi, the most polluted city in the world, suffers from a toxic blend of geography, growth, poor energy sources and unfavourable weather. These in turn boost its dangerously high levels of air pollution.
A team of researchers led by the University of Surrey, U.K., assessed how Delhi's landscape, weather, energy consumption culture, and growing urban population combine to elevate concentrations of air pollutants, the most harmful to human health.
"Air pollution has been placed in the top ten health risks faced by human beings globally. Delhi has the dubious accolade of being regularly cited as the most polluted city in the world, with air pollution causing thousands of excess deaths in a year in this growing megacity," said Dr Prashant Kumar of the University of Surrey.
"While it might be easy to blame this on increased use of vehicles, industrial production or a growing population, the truth is that Delhi is a toxic pollutant punchbowl with myriad ingredients, all of which need to be addressed," said Kumar.
Classed as the world's fifth 'megacity', Delhi has a population of 25.8 million, which continues to grow. With this growth, the study predicted that the number of road vehicles will increase from 4.7 million in 2010 to nearly 26 million by 2030. As a landlocked megacity, Delhi has limited avenues for flushing polluted air out of the city. Delhi's surrounding regions are sometimes even more polluted than the city. For example, most of the brick kilns used for making bricks are not located in the city, but in predominantly upwind surrounding industrial areas, researchers said.
These outside pollutants can be attributed to use of low-quality fuels such as raw wood, agricultural and plastic waste in industrial settings, cow dung for cooking stoves and widespread use of diesel generators. These sources release fine particle pollutants. In Delhi fine particle pollution rates are ten times higher than that of Chennai, which has ten times more cars but is coastally located, without the surrounding industrial areas.
According to a World Health Organisation (WHO) report released in May last year, Delhi was ranked as the most polluted city in the world.