Air Pollution

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

Photochemical smog is mainly composed of ozone, nitrogen dioxide and volatile organic compounds. Sulphur dioxide is not a component of photochemical smog.

The brown haze of photochemical smog is largely attributed to NO₂.

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.

The products of photochemical smog are peroxyacetyl nitrate and ozone. 

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.

Mist forms when water vapor in air condenses into tiny water droplets suspended near the ground. This occurs when warm moist air cools rapidly, typically at night or over cold surfaces. Dry ice and solid carbon monoxide are unrelated to natural mist formation.

Photochemical smog can be suppressed by certain compounds, which act as free radical traps and also by installation of efficient catalytic converters in the automobiles.

When abnormal or excessive components enter the atmosphere beyond normal composition, it results in air pollution which is harmful to human health and the environment. Pollution refers to the presence of harmful substances in the air.

Major primary pollutants produced by human activity include

1. deforestation
2. excessive use of fossil fuels
3. excessive use of fertilizers

Hydrocarbons and nitrogen oxide combine together in the presence of ultraviolet rays to form photochemical smog. It is a thick dark or yellow fog that causes toxic effect on man, animals and plants.

Electrostatic precipitation is used for particulate pollutants. When a gas containing aerosols is passed between two electrodes, aerosol particles get precipitated on the electrode.

Ground level ozone is formed by the reaction of volatile organic compounds with nitrogen oxide. It can cause respiratory diseases.

PCBs are produced by burning plastics. They cause skin conditions like rashes and chloracne.

Carbon monoxide is hazardous to man as CO combines with hemoglobin of the blood which causes the death of a person when a person takes inside the large amount of it in the body.