Health effects of particulate pollutants:
(i) Dust, mist, fumes,etc., are air borne particles which are dangerous for human health. Particulate pollutants bigger than 5 microns are likely to settle in the nasal passage whereas particles of about -10 micron enters the lungs easily and causes scaring or fibrosis of lung lining. They irritate the -lungs and causes cancer and asthma. This disease is also called pneumoconiosis. Coal miners may suffer from black lung disease. Textile workers may suffer from white lung disease.
(ii) Lead particulates affect children's brain, interferes maturation of RBCs and even cause cancer.
(iii) Particulates in the atmosphere reduce visibility by scattering and absorption of sunlight. It is dangerous for aircraft and motor vehicles.
(iv) Particulates provide nuclei for cloud formation and increase fog and rain.
(v) Particulates deposit on plant leaves and hinder the intake of CO₂ from the air and affect photosynthesis.

Non-viable particulates: The non- viable particulates are small solid particles and liquid droplets suspended in air. They help in the transportation of viable particles. There are four types of non-viable particulates in the atmosphere. They are classified according to their nature and size as follows.
(i) Smoke : Smoke particulate consists of solid particles (or) mixture of solid and liquid particles formed by combustion of organic matter
Example: cigarette smoke, oil smoke, smokes from burning of fossil fuel, garbage and dry leaves.
(ii) Dust : Dust composed of fine solid particles produced during crushing and grinding of solid materials.
Example : sand from sand blasting, saw dust from wood works, cement dust from cement factories and fly ash from power generating units.
(iii) Mists: They are formed by particles of spray liquids and condensation of vapours in air.
Example: sulphuric acid mist, herbicides and insecticides sprays can form mists.
(iv) Fumes : Fumes are obtained by condensation of vapours released during sublimation, distillation, boiling and calcination and by several other chemical reactions.
Example : organic solvents, metals and metallic oxides form fume particles.

(i) Rain water normally has a pH of 5.6 due to dissolution of atmospheric CO₂ into it. Oxides of sulphur and nitrogen in the atmosphere may be absorbed by droplets of water that make up clouds and get chemically converted into sulphuric acid and nitric acid respectively as a results of pH of rain water drops to the level 5.6, hence it is called acid rain.
(ii) Acid rain is a by-product of a variety of sulphur and nitrogen oxides in the atmosphere. Burning of fossil fuels (coal and oil) in power stations, furnaces and petrol, diesel in motor engines produce sulphur dioxide and nitrogen oxides. The main contributors of acid rain are SO₂ and NO₂.They are converted into sulphuric acid and nitric acid respectively by the reaction with oxygen and water.
2SO₂ + O₂ + 2H₂O ⟶ 2H₂SO₄
4NO₂ + O₂ + 2H₂O ⟶ 4HNO₃
Harmful effects of acid rain:
(i) Acid rain causes extensive damage to buildings and structural materials of marbles. This attack on marble is termed as stone leprosy.
CaCO₃ + H₂SO₄ ⟶ CaSO₄ + H₂O + CO₂ ↑
(ii) Acid rain affects plants and animal life in aquatic ecosystem.
(iii) It is harmful for agriculture, trees and plants as it dissolves and removes the nutrients needed for their growth.
(iv) It corrodes water pipes resulting in the leaching of heavy metals such -as iron, lead and -copper into the drinking water which have toxic effects.
(v) It causes respiratory ailment in humans and animals.

Gaseous air pollutants :
Oxides of sulphur, oxides of nitrogen, oxides of carbon, and hydrocarbons are the gaseous air pollutants.
(a) Oxides of Sulphur :
(i) Sulphur dioxide and sulphur trioxide are produced by burning sulphur containing fossil fuels and roasting sulphide ores. Sulphur dioxide is a poisonous gas to both animals and plants. Sulphur dioxide causes eye irritation, coughing and respiratory diseases like asthma, bronchitis, etc.
(ii) Sulphur dioxide is oxidised into more harmful sulphur trioxide in the presence of particulate matter present in polluted air
\(2S{ O }_{ 2 }+{ O }_{ 2 }\xrightarrow [ ]{ Particulate\quad Matter } 2S{ O }_{ 3 }\)
(iii) SO₃ combines with atmospheric water vapour to form H₂SO₄, which comes down in the form of acid rain.
\(S{ O }_{ 3 }+{ H }_{ 2 }O\longrightarrow { H }_{ 2 }{ SO }_{ 4 }\)
(b) Oxides of nitrogen:
Oxides of nitrogen are produced during high temperature combustion processes, oxidation of nitrogen in air and from the combustion of fuels (coal, diesel, petrol etc.).
\({ N }_{ 2 }+{ O }_{ 2 }\xrightarrow [ ]{ >1210°C } 2NO\)
\({ 2NO }+{ O }_{ 2 }\xrightarrow [ ]{ >1100°C } 2N{ O }_{ 2 }\)
\(NO+{ O }_{ 3 }\longrightarrow N{ O }_{ 2 }+{ O }_{ 2 }\)
(ii) The oxides of nitrogen are converted into nitric acid which comes down in the form of acid rain. They also form reddish brown haze in heavy traffic. Nitrogen dioxide potentially damages plant leaves and retards photosynthesis. NO₂ is a respiratory irritant and it can cause asthma and lung injury. Nitrogen dioxide is also harmful to various textile fibres and metals
(c) Oxides of carbon: The major pollutants of oxides of carbon are carbon monoxide and carbon dioxide.
(i) Carbon Monoxide: 
Carbon monoxide is a poisonous gas produced as a result of incomplete combustion of coal are firewood. It is released into the air mainly by automobile exhaust. It binds with hemoglobin and form carboxy hemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced. This oxygen deficiency results in a headache, dizziness, tension, Loss of consciousness, blurring of eyesight and cardiac arrest.
(ii) Carbon dioxide: Carbon dioxide is released into the atmosphere mainly by the process of respiration, burning of fossil fuels, forest fire, decomposition of limestone in cement industry etc. Green plants can convert CO₂ gas in the atmosphere into carbohydrate and oxygen through a process called photosynthesis. The increased CO₂ level in the atmosphere is responsible for global warming. It causes headache and nausea.
(d) Hydrocarbon:
(i) The compounds composed of carbon and hydrogen only are called hydrocarbons. They are mainly produced naturally (marsh gas) and also by incomplete combustion of automobile fuel
(ii) They are potential cancer causing (carcinogenic) agents. For example, polynuclear aromatic hydrocarbons (PAH) are carcinogenic, they cause irritation in eyes and mucous membranes.

(a) Environmental Pollution:
(i) Any undesirable change in our environment that has harmful effects on plants, animals and human beings is called environmental pollution
(ii) Environmental pollution is usually caused by the addition of waste products of human activity to the environment. The substances which cause pollution of environment are called pollutants. The pollutants may be solids, liquids or gaseous substances present in significant concentration in the environment. Our environment becomes polluted day by day, by the increased addition of industrial and domestic wastes to it. The air we breathe, the water we drink and the place where we live in, are highly contaminated
(iii) The pollutants ate classified as bio-degradable and non-biodegradable pollutants.
(b) Bio-degradable pollutants:
(i) The pollutants which can be easily decomposed by the natural biological processes are called bio-degradable pollutants
(ii) Examples: plant wastes, animal wastes etc.
(c) Non bio-degradable pollutants:
(i) The pollutants which cannot be decomposed by the natural biological processes are called Non bio-degradable pollutants
(ii) Examples: metal wastes (mainly Hg and Pb), DDT, plastics, nuclear wastes etc., These pollutants are harmful to living organisms even in low concentration. As they are not degraded naturally, it is difficult to eliminate them from our environment