Biology [5 Mark Question Answer]

Ozone depletion and global warming are separate problems, though some agents contribute to both. Chlorofluorocarbons (CFCs) are the principle cause of ozone depletion, but they also happen to be potent heat-trapping gases. Still, CFCs are responsible for less than 10 per cent of total atmospheric warming, far less than the 63 percent contribution of carbon dioxide. Thus, attention paid to CFCs has been on their ozone depletion role. This will change as CFCs are phased out and replaced by hydro chlorofluorocarbons (HCFCs) and hydro fluorocarbons (HFCs such as R-134a). These chemicals have little or no effect on the ozone layer but are strong heat-trapping gases. As their concentration in the atmosphere is already rising, the likely net effect in the future is that reductions in the CFC-related contribution to global warming will be offset by the presence of HCFCs and HFCs

The upper part of stratosphere contains large amount of Ozone gas. The ozone gas blocks the harmful ultraviolet rays reaching earth. It has been proved that chlorofluorocarbons or CFC are released from the refrigeration system, air conditioning systems, spray cans etc. These CFC’s are light and are able to reach at height of stratosphere. Here they react with the ozone gas. In this process the chlorine gas is released which reacts with the ozone gas. It breaks apart the ozone molecules thus reducing them in the stratosphere. As a result, the ultraviolet radiation is able to reach the surface of earth. These rays can cause skin cancer, cataract and affect the immune system of the body.

Acid Deposition: Commonly called acid rain is caused by emissions of sulphur dioxide and nitrogen oxides. Although natural sources of sulphur oxides and nitrogen oxides do exist, more than 90% of the sulphur and 95% of the nitrogen emissions occurring in eastern North America are of human origin. These primary air pollutants arise from the use of coal in the production of electricity, from base-metal smelting, and from fuel combustion in vehicles. Once released into the atmosphere, they can be converted chemically into such secondary pollutants as nitric acid and sulfuric acid, both of which dissolve easily in water. The resulting acidic water droplets can be carried long distances by prevailing winds, returning to Earth as acid rain, snow, or fog.

The impact of pollution on health may be primary or secondary. The primary impact occurs immediately but the secondary impact is delayed and may persist in future.

1. When contaminated water is supplied to the residents of a locality, it may spread water borne diseases like diarrhea, hepatitis etc.
2. Release of smoke as vehicular exhaust pollutes the air. When this air is inhaled by the humans it causes asthma and bronchitis.
3. Large amount of soluble nitrates are released and dissolve in the water. It may contaminate the groundwater including wells of the area. Heavy intake of nitrates by humans may cause serious health hazards.
4. People who work in the deep coal mines, inhale the fine coal dust. It leads to a disease called black lungs. Many gases are also released in the process of mining like methane and carbon-monoxide.