Effects of Air Pollution: on Human Health, Animals and Atmosphere!
Air pollution has now become a worldwide phenomenon and every individual in one way or the other is facing problems caused by it. Its impact can be seen locally, at regional level as well as at global level.
At local and regional levels its manifestations are in the form of alterations in (i) visibility, (ii) intensity of sunshine, (iii) precipitation amount, and (iv) acid rain. Its global effects are. (i) Change in natural climate by rise of temperature, melting of snow, (ii) increase in carbon dioxide, (iii) increase in particulates, (iv) holes in ozone layer, etc. Several aspects of air pollution, such as effects on the ozone layer, greenhouse effect, smog and acid rain have already been discussed.
The effects of air pollution can be grouped under the following heads:
(i) Effects on human health,
(ii) Effects on animals and plants,
(iii) Effects on atmosphere, and
(iv) Other effects.
1. Effects on Human Health:
Some environmental poisons can cause acute illness and even death. Others may be harmful, but the disease may take years or even decades to appear. Air pollution mainly affects the respiratory system.
Bronchitis, emphysema, asthma and lung cancer are some of the chronic diseases caused due to exposure to polluted air. It is feared that lung cancer is caused mainly due to polluted air because carcinogens are found in it. Its mortality rate is higher in urban areas.
Figure 7.1 shows the various effects of air pollution on the human body. Sulfur dioxide is the most serious and widespread air pollutant. Its lower concentration is a cause of spasms in the smooth muscle of bronchioles and its higher concentration induces increased mucus production.
Sulfur dioxide is also considered to cause cough, shortness of breath, spasm of the larynx and acute irritation to the membranes of the eyes. It also acts as an allergenic agent. When it reacts with some compounds, sulfuric acid is formed which may damage lungs.
Carbon monoxide often affects the oxygen carrying capacity of blood. Nitric oxide is reported to be a pulmonary irritant and its excess concentration may cause pulmonary haemorrhage.
Hydrogen sulfide is also toxic. Lead emitted from automobile exhausts is a cumulative poison and is dangerous particularly to children and may cause brain damage.
The particulate pollutants such as asbestos, silica, carbon, beryllium, lead, etc., are capable of exerting a noxious (fibrotic) local action in the interstitial areas of the lungs. Radioactive elements are also harmful to man and other living organisms. As described earlier, smog has a killer effect, which is also the result of air pollution. The death toll by smog varies from few persons to thousands.
In December 1952, about 4,000 persons died in London due to smog. Similar cases have been reported from London itself in 1956, 1957 and 1962 in which the death toll was between 700 and 1,000 persons. In other countries also smog deaths have been reported. In fact, the growing air pollution has now become a health hazard for man.
2. Effects on Animals and Plants:
The impact of air pollution on animals is more or less similar to that on man. Chronic poisoning results from the ingestion of forage contaminated with atmospheric pollutants. Among the metallic contaminants, arsenic, lead and molybdenum are important. Fluoride is another pollutant, which causes fluorosis among animals.
A number of livestock have been poisoned by fluorides and arsenic in North America. Bone lesions in animals due to excessive fluorides have also been reported.
Air pollution has caused widespread damage to trees, fruits, vegetables, flowers and in general, vegetation as a whole. The total annual cost of plant damage caused by air pollution in USA alone has been estimated to be in the range of 1 to 2 billion dollars. The most dramatic early instances of plant damage were seen in the total destruction of vegetation by sulfur dioxide in the areas surrounding smelters.
When the absorption of sulfur dioxide exceeds a particular level, the cells become inactive and are killed, resulting in tissue collapse and drying of leaves. Cotton, wheat, barley and apple are more sensitive to this pollutant.
Fluorides are responsible for various types of injuries to plants. The leaves of apple, apricot, fig, peach and prune are more susceptible to air borne fluorides. Fluorides seem to interfere with the photosynthesis and respiration of plants. Smog also causes injury to plants. Similar impact of ozone can be seen in the lesions to plants. Chlorine, ammonia, hydrogen sulfide, etc., are also harmful to vegetation.
3. Effects on Atmosphere:
Some of the effects of air pollution on atmospheric conditions, such as effect on ozone layer, greenhouse effect, etc., have already been discussed. There is an increase in the carbon dioxide concentration in the air due to increased combustion of fossil fuels. Carbon dioxide absorbs heat strongly and the radiative cooling effect of the earth is thus decreased.
The rising of temperatures and ozone holes are some of the problems which have attracted the attention of the scientists all over the world. These problems are not related to any region or a country but are the global problems and their impact on world climate may be hazardous to the whole world.
The local weather conditions are highly susceptible to air pollution. Its impact on temperature, humidity, rainfall and clouds is apparent. The ‘smog dom’ on large urban centres is the result of air pollution. Due to air pollution, visibility also reduces.
4. Other Effects:
Air pollution can also cause damage to property and materials. The smoke, grit, dust and oxides of sulphur have harmful effects on structures.
In 1972, when an oil refinery at Mathura was opened, its impact on Taj Mahal became a major issue. Sulfur dioxide is the most damaging of gaseous pollutants. Aluminum alloys, copper and copper alloys, iron and steel are corroded when exposed to contaminated air.
Hydrogen sulfide reacts with lead paints to form lead sulfide thereby producing a brown to black discolouration. The damage caused by air pollution to structures is not serious but from an aesthetic point of view, it is not desirable.