High concentration of CO₂ in atmosphere has been the main component of greenhouse effect.

It is a highly dangerous gas with a high potential of causing cancer and respiratory ailments.

The toxic effects of carbon monoxide on human beings and animals arise from its reversible combination with haemoglobin (Hb) in red blood cells, which cause displacement of oxygen. This results in oxygen starvation or anoxia. The maximum permissible concentration of CO in the atmosphere is 40 ppm for an exposure of 8 hours. A higher concentration of CO or a longer exposure starts causing adverse effects. In small amounts, CO causes headaches and fatigue, and in larger doses, it can be lethal.

Inhaling of nitrogen oxides by humans results in pulmonary edema and hemorrhage. Several sensitive plants get adversely affected by NOx even at the concentration of 1 ppm for a day or 0.35 ppm for a few months. The affected plants start shedding their leaves and fruit. Nitrogen oxides cause fading of textile dyes and deterioration of cotton and nylon fabrics.

Exposure to SO₂ causes deterioration of fabrics (cotton, rayon), paper and leather. Being corrosive, it has damaging effects on metals, such as iron, steel, aluminium, and on building materials, such as limestone, marble, roof slate, etc. Marble structures, limestone and geological sources of ammonia act as a sink for atmospheric SO₂.

All of the above are the achievements of green chemistry.

The elements or organisms that can consume a pollutant are known as 'sinks'. Recent researches have shown that soil is capable of removing large amounts of CO from the atmosphere by the action of some soil microorganisms. The microorganisms act as a sink for CO.

It is also a pollutant, when generated in large quantity, because it can reduce the oxygen concentration, in the air. It is a gas produced when fuel is burnt, in adequate oxygen. Normally, the atmospheric air will have 0.03% CO₂ When it's concentration increases due to pollution, it reduces the percentage of oxygen in the atmosphere.

Hydrogen sulphide (H₂S) is one of the dangerous, pungent pollutant gases with many deleterious effects on the respiratory tract. It is released by many industries as a part of the sulphonation process.

When cyanide chemicals are used in the manufacturing process, hydrogen cyanide is formed as a by product. It is a highly corrosive and poisonous gas, leading to eye irritation, respiratory problems as well as other complications. In high doses, it can cause death.

All of the above are factors responsible for air pollution.

All of the above are gaseous pollutants.

In many industries, ammonia gas is used as a reducing agent. It is a corrosive gas with a high potentiality of causing throat irritation, burning of pharynx, oesophagus, etc. It can also cause digestive problems when excess gas is inhaled.

Cardiovascular disorders are mainly caused by factors, such as high cholesterol level, smoking, obesity, stress, diabetes, genetics and lack of exercise.

The high concentration of CO₂ in atmosphere has been the main component of the greenhouse effect, which has caused global warming, i.e. the rise of atmospheric temperature in recent years.

H₂S gas is extremely toxic to humans. In higher atmospheric concentrations, it can be fatal. The reaction of H₂S with essential proteins is primarily responsible for it's toxic effects.

The greenhouse effect, is a process by which thermal radiation from a planetary surface, is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere. As a result, the temperature there is higher, than it would be, if direct heating by solar radiation. were the only warming mechanism.

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SO₂ is poisonous, and irritates the respiratory system of animals and humans. A continuous exposure to concentration of 0.2 ppm lasting for 3-4 days or even 0.5ppm for full day has been reported to damage the lungs and increase the rate of mortality. In plants and grasses, SO₂ also produces leaf injuries (called necrotic blotching). Sulphur dioxide damages, barley, alfalfa, cotton and wheat.

Sulphur dioxide is a gaseous pollutant which is capable of forming sulphuric acid.

Smog is a mixture of smoke and fog. 

In many industries, ammonia gas (NH₃) is used as a reducing agent. It is a corrosive gas with a high potentiality of causing throat irritation, burning of pharynx, oesophagus, etc. It can also cause digestive problems when excess gas is inhaled.

Sulphur dioxide (SO₂) is a dangerous pollutant with a potential to form sulphuric acid when mixed with water vapours.

The life threatening effects of carbon monoxide arise from its reversible combination with haemoglobin (Hb) in red blood cells, which causes displacement of oxygen. This results in oxygen starvation or anoxia.

SO₂ is poisonous and irritates the respiratory system of animals and humans. A continuous exposure to concentration of 0.2 ppm lasting for 3-4 days or even 0.5 ppm for full day has been reported to damage the lungs and increase the rate of mortality. In plants and grasses, SO₂ also produces leaf injuries, called necrotic blotching. Sulphur dioxide damages barley, alfalfa, cotton and wheat.