Understanding Indian Air Quality Index(AQI)

In Air Pollution by Nirvana

In an attempt to make air quality measurement easier to understand, the ministry of environment and forests launched a National Air Quality Index (AQI). It will put out real time data about level of pollutants in the air and inform people about possible impacts on health.

Government have added five more components to the new measurement process: Particulate Matter 2.5, ozone, carbon monoxide, ammonia and lead

The index classifies air quality simply as good, satisfactory, moderately polluted, poor, very poor, and severe. Each band is represented by a colour code to visually express the level of severity that people can grasp easily.

 

The index will cover Delhi, Agra, Kanpur, Lucknow, Varanasi, Faridabad, Ahmedabad, Chennai, Bengaluru and Hyderabad. The index will be later expanded to 46 more cities having a population of more than one million, besides 20 state capitals

 

Eight pollutant have been taken into account to calculate AQI

  • Nitrogen oxide
  • Sulpher dioxide
  • PM2.5
  • PM 10
  • Ozone
  • Carbon monoxide
  • Ammonia
  • Lead

The AQI has been developed by the Central Pollution Control Board in consultation with IIT-Kanpur and an expert group comprising medical, air-quality professionals and other stakeholders

 

Additional Information (Particulate matter)

 

They are Also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid droplets. Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles.

They can come in almost any shape or size, and can be solid particles or liquid droplets. We divide particles into two major groups. These groups differ in many ways. One of the differences is size, we call the bigger particles PM10 and we call the smaller particles PM2.5.

BIG. The big particles are between 2.5 and 10 micrometers (from about 25 to 100 times thinner than a human hair). These particles are called PM10 (we say “P M ten”, which stands for Particulate Matter up to 10 micrometers in size). These particles cause less severe health effects.

SMALL. The small particles are smaller than 2.5 micrometers (100 times thinner than a human hair). These particles are called PM2.5 (we say “P M two point five”, as in Particulate Matter up to 2.5 micrometers in size).

 

 

 

Coarse Particles (PM10) Fine Particles (PM2.5)
What they are
  • smoke, dirt and dust from factories, farming, and roads
  • mold, spores, and pollen
  • toxic organic compounds
  • heavy metals
How they’re made
  • crushing and grinding rocks and soil
  • then blown by wind
  • driving automobiles
  • burning plants (brush fires and forest fires or yard waste)
  • smelting (purifying) and processing metals

Particulate Matter and India

The PM2.5 is particularly dangerous and can cause adverse health effects owing to its greater penetrability into the human respiratory system and eventual accumulation in human organs and blood. Rural women, children and elderly population are more prone to diseases caused by air pollution. Rural women, in particular, face a greater risk from indoor pollution — locally made mud stoves fuelled by solid biofuel emit a far greater amount of finer particulate matter.

Air quality of any area depends on local emissions, long-range transport, local and regional weather patterns, and to some extent the topography of the region. Due to increased buoyancy and efficient ventilation in summer, pollution plumes rise effortlessly to the free atmosphere. This leads to a reduced level of surface level PM2.5 concentration in our breathing zone. The problem gets aggravated during winter. Adverse conditions during winter help trapping of pollution leading to elevated level of surface PM concentration.

Compared with peninsular India and coastal regions, the situation is far worse in the Gangetic Basin, especially during winter months. The Himalayas act as a barrier to dissipation of pollution plumes emanating from the cities located in the Basin. As a result, cities in the Basin are more prone to sustained bad air quality.

While the National Air Quality index has created greater awareness of air pollution amongst the masses, there is a need for more concrete action to reverse air pollution.