Air pollution is defined as the presence of any liquid or gaseous substances in the atmosphere in such a concentration which tends to be injurious to man, animals, plants or environment.
The Air Act was passed under Article 253 of the Constitution of India and in pursuance of decisions of Stockholm Conference.
- Objective: to provide means for the prevention, control and abatement of air pollution in order to preserve the quality of air.
- Define terms: such as air pollution, air pollutants, vehicular exhausts and industrial plants etc.
- The Act also includes automobiles, diesel vehicles, transport, railways and domestic fuels.
- Demarcate high pollution areas: The Act provides the declaration of certain heavily polluted areas as Air pollution control area and no industrial plant shall be operated in these areas without prior consent of the State Pollution Control Board.
- Pollution boards duties: The Central and State Water Boards have been entrusted with the task of controlling and preventing air pollution. The State Boards have to lay down and enforce standards for prevention and control of air pollution.
- Emission control: The State Government and the respective Board(s) may give instructions to the concerned Authority in-charge for Registrations under the Motor Vehicles Act, 1939, to ensure emission standards for automobiles. Failure to comply with the conditions prescribed for this purpose is punishable with fine and imprisonment.
- Penalty on polluter: The State Boards have powers to sue a polluter in a court of law to punish him for polluting the air and the expenses incurred by the Board will be recovered from the polluter.
- Noise as pollution: The Act also includes noise under the category of air pollutants in 1987.
Classification of Air Pollutants
According to the form in which they persist after release into the environment.
- Primary pollutants: These are persistent in the form in which they are added to the environment, e.g. DDT, plastic, CO, CO2, oxides of nitrogen and sulphur, etc.
- Secondary Pollutants: These are formed by interaction among the primary pollutants. For example, peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides and hydrocarbons.
According to their existence in nature
- Quantitative Pollutants: These occur in nature and become pollutant when their concentration reaches beyond a threshold level. E.g. carbon dioxide, nitrogen oxide.
- Qualitative Pollutants: These do not occur in nature and are human-made. E.g. fungicides, herbicides, DDT etc.
Particulate pollutants
- Particulate pollutants are matter suspended in air such as dust and soot.
- Major source of SPM (suspended particulate matter) are industries, vehicles, power plants, construction activities, oil refinery, railway yard, market place, industries, etc.
- Their size ranges from 0.001 to 500 micrometres (µm) in diameter.
- Particles less than 10 µm float and move freely with the air current.
- Particles which are more than 10 µm in diameter settle down.
- Particles less than 0.02 µm form persistent aerosols.
- According to the Central Pollution Control Board (CPCB), particulate size 2.5 µm or less in diameter (PM 2.5) are responsible for causing the greatest harm to human health.
- These fine particulates can be inhaled deep into the lungs and can cause breathing and respiratory symptoms, irritation, inflammations and pneumoconiosis (disease of the lungs caused due to inhalation of dust. It is characterised by inflammation, coughing, and fibrosis – excess deposition of fibrous tissue).
Fly ash
- Fly ash is ejected mostly by thermal power plants as by-products of coal burning operations.
- Fly ash pollutes air and water and may cause heavy metal pollution in water bodies.
- Fly ash affects crops and vegetation as a result of its direct deposition on leaf surfaces.
Composition
- Fly ash particles are oxide rich and consist of silica, alumina, oxides of iron, calcium, and magnesium and toxic heavy metals like lead, arsenic, cobalt, and copper.
- Major oxides are present are aluminium silicate (in large amounts), silicon dioxide (SiO2) and calcium oxide (CaO).
NAAQS
- The Central Pollution Control Board (CPCB) has instituted National Ambient Air Quality Standards (NAAQS), ensuring consistent air quality standards across the country.
- The National Clean Air Programme (NCAP) was introduced nationwide in 2019 with the objective of reducing particulate matter levels by 20–30% in 132 cities by 2024.
- Failure to consistently meet the National Ambient Air Quality Standards (NAAQS) over a five-year period categorizes a city as non-compliant.
NAAQ Standard
- The Air (Prevention and Control of Pollution) Act empowers the Central Pollution Control Board (CPCB) to establish air quality standards.
- Subsequently, in November 2009, the CPCB introduced the prevailing National Ambient Air Quality Standards.
- The regulations set in 2009 standardized national air quality benchmarks and significantly reduced the permissible limits for various pollutants.
The standards are categorized into two types:
- Primary Standards: These are designed to safeguard human health with an ample margin of safety, considering vulnerable groups such as young children, the elderly, and individuals with respiratory conditions.
- Secondary Standards: Formulated to protect against any known or anticipated adverse effects of a pollutant on public welfare, property, traffic safety, economic values, and personal comfort and well-being.
Pollutants Covered
The National Ambient Air Quality Standards encompass a range of pollutants, including:
- Sulphur dioxide (SO2)
- Nitrogen dioxide (NO2)
- Particulate matter with a size less than 10 microns (PM10)
- Particulate matter with a size less than 2.5 microns (PM2.5)
- Ozone
- Lead
- Carbon monoxide (CO)
- Arsenic
- Nickel
- Benzene
- Ammonia
- Benzopyrene
