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1. Cars free us from here and now; they turn the difficulties of a journey into the pleasures of a trip. Sure, they have their downside -pollution, noise, - but no amount of environmental damage can ever take the sweetness out of a ride. However, a continuous increase in-the number of cars leads to serious congestion and escalate pollution caused by cars. Governments build new roads trying to improve the situation- but this means that they cut down trees and destroy more of the countryside.
2. The car is one of the biggest polluters today. Exhaust fumes from cars are the main cause of bad air quality, which can make people feel ill and have difficulty breathing. The problem is especially bad in some cities, where on days, when there is not much wind; a brown layer smog (mixture of fog and smoke) hangs in the air. The relatively inefficient combustion of fuel in a car engine cause many hydrocarbon fragments to be left unburned. These fragments (mainly methane) help to form smog and are believed to be carcinogenic.
The incomplete combustion of fuel produces also carbon monoxide (CO). It is poisonous and at moderate concentrations can cause drowsiness and impair mental and physical alertness. Carbon monoxide emissions largely come from cars exhaust. Nitrogen oxides (NO) are formed within the cylinders of an engine during fuel combustion. They are major components of smog.
3. Hydrocarbons and nitrogen oxides in vehicle exhausts combine with one another in sunlight to produce ozone. The ground level ozone is major air pollutant. The photochemical smog is worst in traffic-congested cities on dry, hot summers, whereas sulphur based smog occurs on cold winter days. Photochemical smog is common when the vehicle engines are old and poorly maintained, as often occurs in developing countries. In some overpopulated cities such as Mexico-City and San Paulo almost all children suffer from coughs and wheezing, different forms of allergies. This is mainly due to the effect of ozone and other motor vehicle pollutants.
4. Air in large cities contains a great deal of dust – suspended in air minute solid particles. Some of them are toxic and can contain lead. Lead comes from petrol, it is emitted in tiny particles and if it is breathed in, can accumulate in the body and cause lead poisoning. Human being cannot excrete lead, so it accumulates lead in the body. Even in tiny concentrations, it can cause headaches, abdominal pains, and general tiredness. Today more cars are made to run on unleaded gasoline.
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