Context: As the winter is approaching,  peaking of air pollution is very common in Delhi. 

More on the news:

  • Recently, the air quality index (AQI) slipped into the ‘very poor’ category while some parts of the city saw AQI turn ‘severe’. 
  • Real-time air quality monitoring data from the Central Pollution Control Board (CPCB) showed high levels of particulate matter of 2.5 and 10 micrometres (PM2.5, PM10).
  • Besides concentration of particulates, the CPCB also monitors gas concentrations of nitrogen dioxide (NO2), ammonia (NH3), sulphur dioxide (SO2), carbon monoxide (CO), and ozone (O3). 

Major pollutants causing pollution peaks in Delhi:

  1. Particulate Matters: 
    • Source of emissions: Combustion of diesel and petrol in engines, combustion of solid fuel for energy production, construction and industrial activities, and erosion of pavement by road traffic are some of the primary sources of PM, but they are also formed in the atmosphere through chemical reaction of gaseous pollutants.
    • PM2.5 and PM10: These are mixtures of solid and liquid particles generally having diameters of or less than 2.5 and 10 micrometres, which is smaller than the diameter of a single strand of average human hair, which is about 70 micrometres.
    • Chemical composition: Their physical and chemical characteristics vary by location, and common chemical composition includes nitrates, sulfates, ammonium, and also metals and biological components. 
    • Health risks: As per a World Health Organisation (WHO) report, health effects of inhalable particulate matter, due to short term and long term exposure, include aggravation of respiratory and cardiovascular problems and also mortality from these problems and lung cancer.
      • For mortality, and especially as a consequence of long-term exposure, PM2.5 is a stronger risk factor than the coarse part of PM10.
    • Causing threats in India: A 2017 study found that India had one of the highest annual exposure to PM2.5 levels in the world in 2017, with highest exposure being in Delhi.
      • The study attributed 6.7 lakh deaths in the country to outdoor particulate matter air pollution and 4.8 lakh deaths due to household air pollution. 
  2. Nitrogen dioxide (NO2):
    • Source: It gets in the air from burning of fuel, from sources including emissions from vehicles and power plants. 
    • Health risks: The United States Environmental Protection Agency (EPA) states that 
      • Short-term exposure to high levels of NO2 can aggravate respiratory diseases like asthma, and lead to other problems such as coughing or difficulty breathing. 
      • Long-term exposure may also contribute to development of asthma and could increase susceptibility to respiratory infections.
  3. Ammonia (NH3): 
    • It is another gaseous pollutant that occurs naturally in air, soil and water, and is used as an agricultural fertiliser and in cleaning products. 
    • Short-term inhalation of high levels of ammonia can cause irritation and serious burns in the mouth, lungs and eyes. 
    • Chronic exposure to airborne ammonia can increase the risk of respiratory problems, including impaired lung function.
  4. Sulphur dioxide (SO2): 
    • A Greenpeace report from 2019 had found that India was the largest emitter of SO2 in the world due to burning of coal.
    • Source: The largest source of SO2 in the atmosphere is burning of fossil fuels by power plants and other industrial facilities. 
    • Short-term exposure to SO2 can harm the respiratory system, making breathing more difficult. 
    • SO2 emissions in the air can also lead to formation of other sulphur oxides (SOx), which can react with other compounds in the atmosphere and form particulate matter.
  5. Ozone (O3): 
    • It occurs both in the Earth’s upper atmosphere and at ground level. 
    • At ground, O3 is created by chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds. 
    • Ozone can trigger a variety of health problems, including chest pain, throat irritation and airway inflammation. It can also reduce lung function, harm lung tissue, worsen bronchitis, emphysema and asthma.

Various factors that deteriorates Delhi’s air quality this time of the year:



Images source: Indian Express

Source: IE