What :

• Term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.
• Particles can be suspended in the air for long periods of time.
• Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope.
• Many manmade and natural sources emit PM directly or emit other pollutants that react in the atmosphere to form PM.
• These solid and liquid particles come in a wide range of sizes.
• Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system.
• Particles less than 2.5 micrometers in diameter (PM2.5) are referred to as “fine” particles and are believed to pose the greatest health risks.
• Particles with diameters between 2.5 and 10 micrometers are referred to as “coarse.
• Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs.

Sources

• Include all types of combustion activities (motor vehicles, power plants, wood burning, etc.) and certain industrial processes.
• Coarse particles include crushing or grinding operations, and dust from paved or unpaved roads.
• Other particles may be formed in the air from the chemical change of gases. They are indirectly formed when gases from burning fuels react with sunlight and water vapor. These can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes.

What is in news : Uttar Pradesh is the largest emitter of PM2.5, the class of particulate matter considered most harmful to health, according to an analysis by the Council on Energy, Environment and Water (CEEW).

Other Details :

• The five data sources used are: Emissions Database for Global Atmospheric Research (EDGAR), maintained by the European Commission’s Joint Research Centre; Evaluating the Climate and Air Quality Impacts of Shortlived Pollutants (ECLIPSE), maintained by the International Institute for Applied Systems Analysis (IIASA); Regional Emission Inventory in Asia (REAS), maintained by the National Institute for Environmental Studies, Japan (NIES); Speciated Multipolluter Generator (SMoG), maintained by the Indian Institute of Technology (IIT Bombay); and spatially resolved pollution emission inventory for India, maintained by The Energy and Resources Institute (TERI).
• There are differences in the periods over which these sources track the emissions as well as the pollutants, but most track the important ones: PM2.5, PM10, NOx (nitrous oxides), SO2 (sulphur dioxide), CO (carbon monoxide), NH3 (ammonia), and NMVOC (non-methane volatile organic compounds).
• The high emissions from U.P. were largely due to a significant share of PM2.5 emissions from solid-fuel use in households and, by virtue of being India’s most populous State, it had a higher proportion of households relying on this form of fuel.
• Maharashtra, Gujarat, Odisha, West Bengal, Madhya Pradesh, Bihar, Tamil Nadu, and Rajasthan too feature in the list of top polluters but are differently ranked by the five sources.