consists of roughly 78.09% nitrogen, 20.94% Oxygen, 0.93% Argon, 0.0318% carbon dioxide and small amounts of other gases (by volume). Air also contains a variable amount of water vapor, on average around 1%.

    But with growth of urbanization and industrialization a lot of other elements have been added to pure air. This resulted in the increase of pollution. In order to prevent control and abate air pollution, the Air (Prevention and Control of Pollution) Act was enacted in 1981. According to Section 2(b) of Air (Prevention and control of pollution) Act, 1981 'air pollution' has been defined as 'the presence in the atmosphere of any air pollutant'. As per Section 2(a) of Air (Prevention and control of pollution) Act, 1981' air pollutant' has been defined as 'any solid, liquid or gaseous substance [(including noise)] present in the atmosphere in such concentration as may be or tend to be injurious to human beings or other living creatures or plants or property or environment'. Therefore ambient air quality standard is developed as a policy guideline that regulates the effect of human activity upon the environment so that pollutant emission into the air can be regulated.

The objectives of air quality standards are;
	To indicate the levels of air quality necessary with an adequate margin of safety to protect the public health, vegetation and property;
	To assist in establishing priorities for abatement and control of pollutant level;
	To provide uniform yardstick for assessing air quality at national level;
	To indicate the need and extent of monitoring programme.

The revised National Ambient Air Quality Standards notified on November 2009 is depicted below
Revised National Ambient Air Quality Standards (NAAQS)
[NAAQS Notification dated 18th November, 2009]

* Annual Arithmetic mean of minimum 104 measurements in a year at a particular site taken twice a week 24 hourly at uniform interval.
** 24 Hourly 08 hourly of 01 monitored values, as applicable shall be complied with 98% of the time in a year. 2% of the time, they may exceed the limits but not on two consecutive days of monitoring.

  National Air Quality Monitoring Programme(NAMP)

    Central Pollution Control Board initiated National Ambient Air Quality Monitoring(NAAQM) programme in the year 1984 with only seven monitoring stations in the country. Further, it has been strengthen by increasing the number of monitoring stations with two monitoring stations in currently existing Bihar. The one monitoring station is situated at Beltron Bhawan, Shastri Nagar, Bailey Road, Patna and the another at Gandhi Maidan, Patna and the monitoring work is being carried out by the State Pollution Control Board. Later, the programme NAAQM was renamed as National Air Quality Monitoring Programme(NAMP) and their objectives are:

	To determine status and trends of ambient air quality
	To ascertain whether the prescribed ambient air quality standards are violated.
	To identify Non-attainment Cities; To obtain the knowledge and understanding necessary for developing, preventive and corrective measures; and
	To understand the natural cleansing process undergoing in the environment through pollution dilution, dispersion, wind based movement, dry deposition, precipitation and chemical transformation of pollutants generated.

  The following parameters are being monitored under the NAMP in Bihar

	Sulphur Dioxide(SO2).
	Oxides of Nitrogen(NOx).
	Respirable Particulate Matter(RSPM) or ,PM10. and
	Suspended Particulate Matter(SPM).

  The Central Pollution Control Board has classified the air quality into the following four broad   categories

Pollution Level Classification

Analysis of last ten years air quality data shows a more or less stable trend for SO₂ & NO₂ however, SPM and RSPM show an increasing trend and exceeds the NAAQS.

  Background of Parameters

    Sulphur dioxide (SO₂) is a colorless, soluble gas with a characteristic pungent smell. It is a chemical compound produced by volcanoes and in various industrial processes and are also a precursor to particulates in the atmosphere. Its natural source is volcanic eruption (67%) and anthropogenic sources are combustion of fossil fuel (Coal, heavy fuel oil in thermal power plants and factories), paper Industry, Extraction & distribution of fossil fuels, smelting of metals (sulfide ores to produce copper, lead and zinc), petroleum refining, combustion process in diesel, petrol, natural gas driven vehicles. SO₂ is always accompanied by a little amount of SO₃ and in ambient air it can also affect human health. It also causes visibility impairment. It is considered more harmful when particulate and other pollution concentrations are high. The atmospheric SO_X are converted into H₂SO₄ by the processes of photochemical reactions and ultimately come to the earth surface in the form of acid rain.

Oxides of Nitrogen(NO_X) are a generic term for a group of highly reactive gases that contain nitrogen and oxygen in varying amounts(nitric oxide-NO and nitrogen dioxide-NO₂). NO is a colourless, odourless gas, but Nitrogen dioxide (NO₂) is a reddish-brown toxic gas with a characteristic sharp, biting odor and is a prominent air pollutant. Oxides of nitrogen are formed during combustion processes at high temperatures from the oxidation of nitrogen in air. NO_X are emitted as nitrogen oxide (NO) which is rapidly oxidized to more toxic nitrogen dioxide (NO₂). Sources of nitrogen oxides includes lightning, forest fires, bacterial activity of soil as natural source and vehicles, industrial processes that burn, high temperature combustion (internal combustion engines, fossil fuel-fired power stations, industrial, burning of bio-mass) and fossil fuels are anthropogenic sources. NO₂ irritates the nose and throat increase susceptibility to respiratory infections. In addition, NO_X is a potent and selective vasodilator in pulmonary arterial hypertension. Oxides of nitrogen react with Volatile Organic Compounds (VOC_S) to form ground level ozone. They also react to from nitrates, acid aerosols. Almost all NO_X is emitted as NO, which is rapidly oxidized to more toxic NO₂. They also contribute to nutrient overload that deteriorates water quality. The atmospheric NO_X also converted into HNO₃ by the processes of photochemical reactions and ultimately precipitated as nitrate salts in either rainfall(as acid rain) or as dust and then come to the earth surface.

Particulate Matter: Small, solid particles and liquid droplets are collectively termed as particulates. These are present in the atmosphere in large numbers. Particle pollution, also called particulate matter or PM, is a complex mixture of extremely small particles and liquid droplets in the air. Their most important property is size, which range in the atmosphere from a diameter of 0.0002μ to a diameter of 500μ.It is known that particulate matter burden of air is less important than the chemical nature and size of the particles. There are various particulates which may present in the atmosphere, such as Fine Particles(less than 100 μ in diameter),Coarse Particles(greater than 100 μ in diameter),Dust(solid particles larger than colloidal-size particles in atmosphere, which are known as Aerosols, contains particles of size ranging from 1 to 200 μ),Aerosol(air borne suspensions either solid or liquid and size generally ⩽1μ),Smoke(may be either liquid or solid, particle size ranging from 0.01 to 1 μ),Fumes(solid particles released from chemical or metallurgical processes, size ranging from 0.1 to 1 μ), Ultrafine particles (UFP)[size ⩽ 0.1µm] and Mist ,Fog & Smog(size generally less than 10 μ).

   Particle pollution also is the main cause of environmental problems. When breathed in, these particles can reach the deepest regions of the lungs. Exposure to particle pollution is linked to a variety of significant human health problems.

Suspended Particulate Matter (SPM) are the bigger than coarse particles, these settle down fast and does not reach the respiratory tract. Therefore they have less adverse effect on health. As a result it has not been included in the revised standard. The factors responsible for high SPM are extensive urbanization and construction activities, vehicular, vehicular population increase, frequent use of captive power generation unit/domestic generation, extensive use of fossil fuel and biomass (wood, leaves etc.) as well as particulate contribution from biological debris. The SPM is also affected with the seasonal variation.

The Central Govt. first issued standards for suspended particulate matter in 1994. In November 2009, the Central Govt. revised the 1994 standards in which SPM was revoked and fine particles (PM_2.5, size 2.5 micrometers in diameter and smaller) has been included.

Respirable Suspended Particulate Matter,[RSPM or Particuate Matter (Size <10 µm) or PM₁₀] consist of particles with a diameter up to 10µm. The major constituents of RSPM are organic and elemental carbon, metals/elements + like silicon. magnesium, iron, ion ions like sulphates, nitrates, ammonium etc. PM10 can be formed by physical processes of crushing. grinding and abrasion of surfaces. Mining and agricultural activities are some of the sources of large size particles. The anthropogenic sources are coarse particles and are produced by the mechanical break-up of large solid particles, windblown dust such as road dust, fly ash, soot, agricultural processes, physical processes of crushing, grinding and abrasion of surfaces, photo chemically produced particles, such as those found in urban haze, pollen grains, mould spores, and plant and insect parts and anthropogenic sources are combustion of fossil fuel (Coal, heavy fuel oil in thermal power plants, office, factories), paper Industry, extraction & distribution of fossil fuels, smelting of metals (sulfide ores to produce copper, lead and zinc), Petroleum refining. Combustion process in diesel, petrol, natural gas driven vehicles PM10 can settle in the bronchi and lungs and cause health problems like respiratory illness, visibility impairment, aggravate existing heart and lung diseases. It also causes visibility reduction.

Particulate Matter (Size <2.5 µm) or PM_2.5.
These particles are respirable fraction composed mainly of carbonaceous materials (organic and elemental). inorganic compounds (sulfate, nitrate, and ammonium), and trace metal compounds (iron, aluminium, nickel, copper, zinc, and lead) penetrates deeper into the lungs increases respiratory symptoms, causes irritation of the airways, coughing, or difficulty breathing, decreases lung function; aggravates asthma, chronic bronchitis, irregular heartbeat, nonfatal heart attacks, premature death in people death in people with heart of lung disease

Ammonia(NH3)
   Molecular formula-NH₃; Nature: non-poisonous and basic in nature. It occurs in free state and is present in atmospheric air, natural water (traces),sewage water(high proportion),decaying plant and animal tissues, urine and excreta of animal. It is a colorless gas, lighter than air, that fumes strongly in air and highly soluble in water. It has a sharp burning smell, which brings tears to the eyes and it can damage respiratory system. It increases the heart beat in large doses. Ammonia is produced naturally in large quantities, but it is oxidized to NO₂ and finally to HNO₃ which is washed out by rains or as precipitate of sulphate or nitrate.

Carbon Monoxide(CO)
   Molecular formula-CO. It is a colorless, odorless, tasteless gas, as heavy as air and not soluble in water. It is formed by incomplete combustion of fossil fuel like coal and petroleum, or other organic matter. Automobiles are the commonest source of carbon monoxide pollution in the cities. Other common sources are oil refineries, metallurgical operations and other internal combustion engines. It is a major pollutant for man and animals as it combines with blood hemoglobin much faster than oxygen. Because CO gradually gets oxidized to CO₂, therefore it is not a long range global threat, but in busy area its content rises very much and result reduction in hemoglobin, feeling of headeque and suffocation. Vegetation, Ocean and Soil are the major natural sink of carbon monoxide.

Benzene(C₆H₆) The chemical formula for benzene is C₆H₆, and it has a molecular weight of 78.11 g/mol. Benzene occurs as a volatile,colorless, highly flammable liquid that dissolves easily in water. Benzene has a sweet odor. The vapor is heavier than air and may travel along the ground; distant ignition possible. Reacts violently with oxidants, nitric acid, sulfuric acid and halogens causing fire and explosion hazard. Attacks plastic and rubber. Its vapor/air mixtures are explosive and there is risk of fire and explosion. Benzene is used as a constituent in motor fuels; as a solvent for fats, waxes, resins, oils, inks, paints, plastics, and rubber; in the extraction of oils from seeds and nuts; and in photogravure printing. It is also used as a chemical intermediate. Benzene is also used in the manufacture of detergents, explosives, pharmaceuticals, and dyestuffs.

    Benzene is a toxic air pollutant that can cause serious health effects including cancer. Benzene is found in the ambient air due to emissions from burning of coal and oil, evaporation from gasoline service stations, and motor vehicle exhaust. Other sources include wood smoke and cigarette smoke. Tobacco smoke also contains benzene and accounts for individual exposure to benzene. These sources contribute to elevate level of benzene in the ambient air, which may subsequently be breathed by the public. Benzene is very toxic to aquatic organisms also.

Benzo(a)Pyrene (BaP)-particulate phase only, ng/m
   Benzopyrene or Benzo(a)Pyrene (BaP) is an organic compound with the molecular formula C₂₀H₁₂,high molecular weight, density- 1.24 g/cm³ (25 °C), and 5-ring PAH. BaP is one of the polycyclic aromatic hydrocarbons (PAHs) formed when gasoline(automobile exhaust fumes, especially from diesel engines), garbage or any animal or plant materials burn incompletely or incomplete combustion of organic materials, such as wood or fossil fuels and from coke oven emissions. BaP and PAHs are ubiquitous environmental contaminants and highly carcinogenic. People may be exposed to BaP from air, water, soil, cigarette and other plant product smoke, food and some work environments through inhalation, ingestion and skin contact. Exposure to PAHs may cause harmful health effects.

Ozone(O₃)
   The upper layer of atmosphere, stratosphere consists of considerable amount of ozone (O₃),which protects us from the harmful ultraviolet radiation coming from the sun. Therefore, it is important to maintain the ozone shield. Despite having three atoms of oxygen in ozone, it is harmful in lower layers of the atmosphere near earth’s surface. Ozone is a toxic gas. The majority of the harmful effects of hydrocarbon pollution are not due to the hydrocarbons themselves, but the hydrocarbons and other organic compounds (VOCs) present in the atmosphere oxidize through a series of chemical and photochemical reactions, as a result many noxious secondary pollutants like ozone & others (photochemical smog) are produced, which are harmful to animals, plants and human.

Arsenic(As)
   Arsenic is a naturally occurring element with atomic number 33. It occurs as an impurity in many ores and in coal. It is also found in the natural environment in some abundance as well as in small quantities in rock, soil, water and air. It is present in many different minerals. It is present in the environment both naturally and due to certain human activities. This is a notoriously poisonous metalloid that has many allotropic forms; yellow, black and grey are a few that are regularly seen. Pure arsenic is a gray metal-like material usually found combined with other elements such as oxygen, chlorine, and sulphur. Arsenic and its compounds are used as pesticides, herbicides, insecticides and various alloys. Arsenic in animals and plants combines with carbon and hydrogen to form organic arsenic compounds. Most inorganic and organic arsenic compounds are white or colorless powders that do not evaporate. They have no smell, and most have no special taste. Most arsenic compounds can also dissolve in water. Arsenic cannot be destroyed in the environment. It can only change its form. Arsenic in air will settle to the ground or is washed out of the air by rain. Many arsenic compounds can dissolve in water.

   Industrial processes such as mining, smelting, coal-fired power plants, burning vegetation and volcanoes all contribute to the presence of arsenic in air, water and soil. Environmental contamination also occurs because it is used in agricultural pesticides, preparation of chemicals for timber preservation, paints, dyes, metals, soaps, insecticides and semi-conductors. Apart from its natural occurrence it is also released into the environment through burning fossil fuels, paper production, cement manufacturing also.

Lead(Pb)
   Lead molecular formula: Pb, is a naturally occurring metal found in small amounts in the earth’s crust and most widely used metal after iron. It is a extremely toxic and poisoning heavy metal. There are several uses of lead such as in manufacturing of lead acid batteries, X-ray equipment, lead sheet and pipes, power cables, in brass and bronze alloys, glass making, ceramic glazes, pigments and other paint additives, additions to PVC and an additive in gasoline. The battery industry is now the principle consumer of lead using an estimated 76% of annual primary and secondary lead produced. Lead in gasoline has been the major source of lead emissions to the environment but is now being phased out almost universally and therefore the production and recycling of lead acid batteries is now becoming the most significant source of lead exposure in the country.

    Lead can enter water, air and soil from natural and anthropogenic sources and can cause adverse effects on human body and lead poisoning is a serious health risk to children. Its sources in ambient air are auto exhaust (from gasoline),paints, storage batteries etc. Bihar is rapidly developing its solar power industry considering solar to be a perfect energy option, but according to a new study, side effects of solar power projects can cause lead pollution to our environment.

Nickel(Ni)
Nickel- molecular formula: Ni, is a silvery-white, hard, malleable, ductile, ferromagnetic heavy metal. It is a good conductor of electricity and heat .Atomic number: 28, atomic mass: 58.7 and melting point: 1453°C. Nickel metal is relatively resistant to corrosion. It dissolves in dilute mineral acids and is insoluble in concentrated nitric acid. The vast majority of nickel is used in alloys. It is used to make stainless steel and other metal alloys. It is commonly alloyed with iron, copper (Monel), chromium, aluminium and zinc. Alloys are used in the making of metal coins, jewellery and, in industry, for making metal items. Nickel and nickel compounds are used for nickel electroplating, to color ceramics, to make batteries, for permanent magnet materials, and as catalysts. Nickel acetate is used mainly as a mordant in the textile industry also.

    It is also a major toxic metal. Its sources in ambient air are combustion of coal, diesel and residual oils, tobacco smoke, chemicals and catalyst, steel and non-ferrous alloys manufacture. Cigarette smoke also contains significant quantities of nickel. Nickel was also found in the air as smallest particulate matter emitted from coal-fired power plants, combustion of petroleum coke at refineries and from metal industry.

COMPILATION OF AIR POLLUTANTS, THEIR SOURCES AND EFFECTS

   Air Quality Monitoring Network

All the air quality monitoring programmes in the State are carried out by the State Pollution Control Board. There are 9 Divisions and 38 districts in the state. The cities/towns like Patna, Muzaffarpur, Chapra, Motihari, Siwan, Gopalganj, Samastipur, Madhubani, Munger, Bhagalpur, Purnea, Darbhanga, Betiah and Sasaram are the district head quarters and have significant population more than one lac. Rajgeer in district- Nalanda and Bodhgaya in district-Gaya are tourist places of international level and have their historic importance. Vehicular emissions, industrial emissions and other development & human activities around these cities/towns play significant role in the quality of ambient air.

   At present, there are only two air quality monitoring stations are operational in the state, one at Beltron Bhawan, Patna and another at Gandhi Maidan, Patna. In addition, three monitoring stations namely at: Bodhgaya(Gaya), Barauni(Begusarai) and Muzaffarpur under NAMP are likely to be put into operation very shortly. The State Pollution Control Board has also planed to establish xyz additional new air monitoring stations with the support of state govt. at: Bhagalpur, Purnea, Darbhanga, Rajgeer, Betiah and Sasaram. The scheme is under progress.

   Continuous Ambient Air Quality Monitoring Station(CAAQMS)

      The State Pollution Control board has established continuous air quality monitoring station at Indira Gandhi Science Complex-Planetarium, Patna, It has been inaugurated by the Honbl’e Dy Chief Minister Sri Shushil Modi in July 2011 and is operational now. The State Board is planning to establish more such monitoring stations in every districts of the state.