The atmosphere, that is the largest part of biosphere is a dynamic system. It contains a wide range of solid, liquid and gas from man made and natural sources. These substances can travel through air, disperse and can react with one another. Clean, dry air contains 78.09% nitrogen and 20.94% oxygen by volume. The remaining 0.97% is a mixture of carbon dioxide, helium, argon,krypton, nitrous oxide and xenon.
What are pollutants?
Various contaminants enters atmosphere. The source can be natural or man made. These portions cause toxicity, disease, aesthetic distress, physiological effects or environmental decay. Such are considered as "pollutants".
What is air pollution?
According to Indian Standards Institution " Air pollution is the presence in ambient atmosphere of substances, generally resulting from the activity of man, in sufficient concentration, present for sufficient time and under circumstances which interfere significantly with the comfort, health or welfare of persons or with the full use or enjoyment of property. Air pollution can be considered as " price of industrialisation".
Air pollution is one of the greatest environmental evils. Air pollution makes air life damager. An average man breathes 22000 times a day and takes 16 kg of air per day. The amount is far more than food and water. Such air pollution causes several damage to human health. Some prime factors affecting human health are listed below:
- Nature of pollutant
- Concentration of pollutant
- Duration of exposure
- Health status of receptor
- Age of receptor
Generally, it has great impact on infants, infirms and elders. Also those with chronic disease of lungs and heart are at great risk. The effect of air pollution is worst during winter season, when pollution reaches its peak.
- Due to contact of pollutant with mucous membrane of eye causes eye irritation, red eyes and runny eyes.
- Nose and throat irritation.
- Irritation of respiratory tract.
- Odour nuisance at low concentration are caused by hydrogen sulphide, ammonia and mercaptans.
- Increase in mortality and morbidity rate.
- Chronic diseases like bronchitis and asthma due to sulphur dioxide, nitrogen dioxide, particulate matters and photochemical smog.
- Pollens can lead to asthmatic attacks.
- When carbon monoxide binds with haemoglobin, it increases stress on those suffering from pulmonary and cardiovascular diseases.
- Flouride compounds leads to fluorosis and mottling of teeths.
- Carcinogenic agents can cause cancer.
- Silica particles can cause silicosis.
- Asbestos particles are responsible for asbestosis.
- Heavy metals such as lead may cause poisoning.
Effect of radioactive pollutants
Radioactive pollutants cause damages that are for long time. It can cause damage to somatic cells or genetic cells. If it cause damage to somatic cells, the individual gets affected and the future generation is rescued from its effect but if it attacks genetic cells, the effect can be seen in future generations too. It can cause
Shortening of life span.
Mutation or genetic effects.
It is one of the most irritating gas. It affects mucous membrane. Realease of sulphur in atmosphere leads to sulphuric acid rains. Both sulphur dioxide and sulphur trioxide are harmful but sulphur trioxide is more irritating and can cause severe bronchospasms at relatively low concentration.
It has a strong affinity for haemoglobin. It combines with haemoglobin in blood and forms carboxyhaemoglobin. It reduces the capacity of haemoglobin to carry oxygen to the body tissues. It also affects central nervous system and can cause heart attacks.
Oxides of nitrogen-
Nitrogen dioxide can lead to occupational disease. Among occupations with nitrogen dioxide hazards are manufacture of nitric acid, electric arc welding, exposures of farmers to silage that has high nitrate fertilisation and mining utlilsing nitrogen compounds as explosives. After exposure to about 15 ppm, it can cause eyes and nasal irritation and pulmonary discomfort after exposure to 25 ppm.
Hydrogen sulphide is known for its rotten egg like foul smell. Exposures to hydrogen sulphide for short periods can cause fatigue of the smell sense.
Ozone is useful for protecting us from the Sun's ultraviolet radiation but has some adverse effect on human body. It has an irritant action in the respirtaory tract. It can reach much deeper into the lungs compared to oxides of sulphur.
Fluorides upto certain range are needed by body but its excess is harmful. It can be extremely irritating in the form of hydrogen fluoride and also it is higly corrosive. Fluorine is a cumulative poison.
The main source of lead is autimobiles. Inorganic lead can cause variety of human health disorders. It can affect gastro-intestinal tract, liver and kidney, abnormalities in fertility and pregnancy and mental development of childrens gets affected.
As the name suggests, they are responsible for causing cancer. Examples- poly cyclic organic compounds and some aliphatic hydrocarbons.
Some of hydrocarbons has adverse effect on human. The effect of formaldehyde is quite irrittaing. It can lead to eye and respiratory irritation due to photochemical smog.
Insecticides are harmful for insects but also for humans. They can affect the central nervous system and can attack other vital organs. It can cause premature labour and abortion during preganancy.