Causes of Pollution
Delhi the most polluted mega-city in the world, and 14 of the 15 most polluted cities in the world are in India. So what exactly is causing this pollution?.
The causes of pollution in Delhi vary by source and by month. Delhi experiences vehicular pollution, industrial-based pollution, domestic fuel-burning, as well as pollution caused by open-waste burning, and intermittent activities like fireworks.
Pollution is produced by industrial activities, brick kilns, power plants, and diesel generator sets.
Vehicular pollution comes in the form of exhaust and resuspended dust from both passenger vehicles and freight vehicles. Road dust resuspension and construction can magnify dust-based pollution.
After rice and grains have been harvested, farmers set fire to the straw stubble to quickly clear the field, kill weeds, slugs and other pests to sow new crops. Crop burning or stubble burning is very common in Punjab and Haryana. Smoke from burning in these areas can produce clouds consisting of toxic particulate matter.
Much of the pollution comes from dust in roads, construction sites, rock crushing, among other sources.
Other Factors Affecting Pollution
Weather can worsen pollution. In the winter, pollution (especially particulate matter) is trapped closer to the ground where we breathe. Car emission control systems also work poorly, increasing carbon monoxide, another pollutant. However, even though pollution is much better in the summer, the heat increases the levels of the ozone pollutant.
Time of Day
Time of day matters. The level of ozone pollutant peaks in afternoon to early evening, while carbon monoxide and particulate matter are a problem during morning or evening rushing hours due to increased vehicle exhaust.
The Himalayas stop pollution from being dispersed quickly, so cities in basins have higher pollution levels. In addition, cities near the sea such as Mumbai are helped by sea breezes that disperse pollution. Land-locked cities such as Delhi don't have this advantage, so air pollution can accumulate for longer periods of time there.