Environmental Pollution: Air Pollution

Types of Air Pollutants

1.  Primary Pollutants: Persistent in the form in which they are added to the environment, E.g. DDT etc.
2. Secondary Pollutants: Formed by interaction among the primary pollutants. E.g. Peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides + hydrocarbons.
3. Quantitative Pollutants: Natural substances when their concentration reaches a threshold level. E.g. carbon dioxide, nitrogen oxide, etc.
4. Qualitative Pollutants: Human-made substances. E.g., Fungicides, Herbicides, DDT etc.

Pollutants Based on Size

1. PM 2.5 (matter that has a diameter of 2.5 micrometres or smaller) – PM2.5 is 30 times finer than a human hair. E.g. Arsenic and Nickel. Nickel compounds (Carcinogenic) are emitted from combustion processes like petroleum processing and combustion of fossil fuels in vehicles/ power plants. 
2. PM 1 (size less than 1 μm)  – 70 times finer than human hair. Primary source: vehicular and industrial emissions. Contains more toxins, including metals, can cause lung injury, and lead to gene damage and cancer. 
3. PM 10 (particles with a diameter of 10 micrometres or less)  – Small enough to pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects

Other Major Pollutants

1. Fly Ash
   • Ejected mainly by thermal power plants as a by-product of coal burning.
   • Pollutes air and water, causes heavy metal pollution in water bodies and affects crops and vegetation due to its direct deposition on leaves.
   • Composition: silica, alumina, oxides of iron, calcium, and magnesium and toxic heavy metals like lead, mercury, cadmium, arsenic, cobalt, and copper.
   • Use – can replace cement , better fill material in road construction, reclamation of wasteland.
2. Nanoparticles (NPs) – Natural Sources: forest fires, volcanic eruptions, weathering, dust storms, etc. 
3. Black Carbon (Soot) 
   • Solid, short-lived air pollutant released from incomplete combustion at high-temperature.
   •  Disrupts regional cloudiness and monsoon rainfall. 
   • Most robust absorber of sunlight and heats the air directly.
   • Reduces albedo after deposition on snow by darkening and heating the surface directly.
   • Largest emitters: India and China
4. Carbon Monoxide (CO)
   • Short-life (a few months) in the atmosphere; burns with a blue flame, producing carbon dioxide.
   • Natural Sources: Photochemical reactions in the troposphere; volcanoes, forest fires etc.
   • Anthropogenic sources: IC engine exhaust, partial combustion of other fuels and iron smelting. 
   • Health effects: Poisoning (Poor ventilation, heat management in electronics); toxic when conc.>35 ppm; combines with haemoglobin to produce carboxyhemoglobin, which affects oxygen transport.
   • Environmental effects: formation of tropospheric ozone; elevates methane concentrations (a GHG).
5. Carbon Dioxide(CO2)
   • Colourless & odourless gas (heavier than air).
   •  Natural sources: volcanoes, hot springs, geysers, carbonate rocks (by dissolution in water and acids). Also, groundwater, rivers, lakes, ice caps, glaciers and seawater (due to water solubility). 
   • Effects on Health: Asphyxiant gas (if concentrations >7%), may cause suffocation. 
   • Effects on the Environment: global warming, ocean acidification (dissolves in water to form carbonic acid).
6. Ozone(O3)
   •  Good ozone: Formed in the stratosphere (O2 and UV interact), absorbs harmful UV rays.
   •  Bad Ozone: At the ground level, it is a pollutant, shortlived GHG and is toxic. Some of it is transported from the stratosphere. The rest is formed when carbon monoxide, nitrogen dioxide, and VOC react in the presence of sunlight at the ground level and convert O2 to O3. 
   • Harmful Effects of Ozone: Smog; Itchy and watery eyes; Can affect sensitive vegetation and ecosystems, forests, especially during the growing season; Transported to long distances by wind, thus even rural areas can experience high O3 levels.
7. Nitrogen Oxides (NOx) – IC engines & coal-burning power plants; lightning. Agricultural fertilisation and nitrogen-fixing plants too promote N-fixation by microbes.

Causes of Air Pollution

1. Industrial Emissions: Factories and power plants emit large quantities of pollutants, including sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter (PM). Heavy industries such as cement, steel, and thermal power are significant contributors.
2. Vehicular Emissions:The growing number of vehicles on the road, particularly in urban areas, leads to high levels of pollutants such as carbon monoxide (CO), hydrocarbons (HC), and NOx. Diesel engines are particularly problematic due to their high PM emissions.
3. Burning of Fossil Fuels: Extensive use of coal, oil, and gas for energy production results in significant air pollution. Rural areas also suffer from air pollution due to the burning of biomass for cooking and heating.
4. Agricultural Activities: Crop residue burning, especially in states like Punjab, Haryana, and Uttar Pradesh, contributes to severe air pollution, particularly during the winter months.
5. Construction Activities: Construction and demolition activities generate dust and PM, contributing to air pollution.
6. Waste Burning: Open burning of waste, including plastic and other hazardous materials, releases toxic pollutants into the air.
7. Natural Causes: Dust storms, especially from the Thar Desert, contribute to high PM levels. Forest fires also contribute to air pollution during certain seasons.

Impacts

1. Environment – 
   • Formation smog , acid rain
   • Crop Damage: Pollutants like ozone can damage crops, reducing agricultural productivity.
2. Health Impact
   • Respiratory Diseases: Increased incidence of asthma, bronchitis, and other respiratory conditions.
   • Cardiovascular Diseases: Higher risk of heart attacks and strokes.
   • Cancer: Long-term exposure to air pollution is linked to lung cancer.
   • Premature Deaths: Air pollution is a leading cause of premature deaths in India.

Government Measures to Counter the Issue

• Vehicle Scrappage Policy 2021: All the central and state governments vehicles that have completed 15 years to be scrapped from April 1, 2023. The policy aims to de-register private cars over 20 years old and commercial vehicles over 15 years old. 
• Bharat Stage (BS) norms: Instituted by GoI to regulate the air pollution from motor vehicles by using appropriate fuel and technology. It was introduced in 2000. The norms limit the release of air pollutants such as nitrogen oxides, carbon monoxide, hydrocarbons, particulate matter (PM) and sulphur oxides from vehicles.
• National Air Quality Monitoring Programme – Regular monitoring of four air pollutants at all the locations: Sulphur Dioxide (SO2), Oxides of Nitrogen (NO2), Respirable Suspended Particulate Matter (RSPM / PM10) and Fine Particulate Matter (PM2.5).
• National Ambient Air Quality Standards (NAAQS): It has been developed by the Central Pollution Control Board (CPCB). It is applicable all over the country. The CPCB has been conferred this power by the Air (Prevention and Control of Pollution) Act, 1981.
• SAFAR System 
  • by the Ministry of Earth Sciences (MoES) (not MoEF).
  • Developed by the Indian Institute of Tropical Meteorology (IITM), Pune and is operationalised by the India Meteorological Department (IMD).  
  • Pollutants included: PM1, PM2.5, PM10, Ozone, CO, NOx (NO, NO2), SO2, BC, Methane (CH4), Non-methane hydrocarbons (NMHC), VOC’s, Benzene, and Mercury. 
  • It gives out real-time air quality index on a 24×7 basis with colour-coding (along with 72 hours advance forecast)