Pollution poses serious threat to city dwellers
Dhaka is one of the worst polluted cities in the world. The air we breathe is mixed with smokes from thousands of vehicles moving on its roads. The amount of smoke emission could have been much lower if traffic jam could be eliminated. And no doubt the level of noise is much higher than the tolerable limit. Then not only smoke from cars is polluting the air, Methane, the natural gas being continuously discharged from thousands of kitchens is also adding to the city pollution. To our frustration, the garbage scattered all along the streets are releasing stinky gases. Who knows what harmful bacteria and viruses are coming with our shoes to our houses? To realise the degree of danger posed by the pollution in our city, one has to think that if air mixed with some smoke passes continuously through a plastic tube, its inside surface gets covered with a black layer just after a few hours. Our lung is also a piping system that is inhaling polluted air in and exhausting it out in every breath. Now gauge, what will happen to us after living for a few years in a city which can be logically considered a gas chamber ! With this quality of air, are not the lungs of our children getting translucent? With this type of continuous respiration, will they not fall chronically sick at an early stage of their life? Many questions arise in the weary mind of a conscious citizen. With number of vehicles on road increasing, the volume of fuel burnt is increasing everyday and so the emission. With the size of the city remaining same, proportion of the pollutants in the atmosphere is increasing day by day. Each element of the pollutant gases has a threshold limit, beyond which it may affect human health alarmingly. The atmosphere was full of Oxygen (approximately 23% by mass) and Nitrogen (approximately 77% by mass) with small presence of some other gases. With industrial revolution and invention of diesel engine, harmful and toxic gases started coming into atmosphere. As engine fuel contains carbon, sulphur, nitrogen and combustion occurs at very high temperature inside chambers, unwanted gases such as Oxides of Sulphur and Oxides of Nitrogen are generated. When engine does not operate at its optimum speed and load, some proportion of fuel remains unburnt. In such situation carbon cannot fully burn into Carbon di Oxide, rather it incompletely burns and forms Carbon Mono-Oxide, an invisible poisonous gas that may kill a person if present in atmosphere beyond certain limit. During traffic jam the vehicles are not in operation at optimum speed and load. As a result harmful carbon mono-oxide gas is being generated, which is poisoning our body slowly that may finally lead to a severe illness. Like developed countries we don't monitor the condition of air quality. So we don't know the exact proportion of this gas in the atmosphere of Dhaka City. It must be very high when compared with some cities where there is no such traffic jam. Sulfur in fuel combines with oxygen when fuels are burnt, and produces oxides of sulphur in atmosphere. When sulfur is oxidized, it forms sulfur dioxide or SO2. If more oxidized, it becomes SO3. The oxides of sulphur are now known as SOx. SOx is a pungent, colourless gas that causes respiratory illness when it reaches a certain level. Even at low level, it can be toxic enough to kill plants. SOx when reacts with wet atmosphere, it may form sulphurus or sulphuric acid, which then causes acid rain. Acid rain is harmful to people and other living organisms. Acid rain can also cause serious damage to metal surfaces of industrial complexes, buildings, etc. Acidification of lakes, surface waters, can do damage to aquatic creatures, forests and farms. We are in doubt if our government has any measure in place to monitor acidity of rain water. SOx reduction measures are divided into pre and post. The precautionary measure is “use of low sulfur fuels” (low sulfur oil and coal) or clean fuels (natural gas and LPG) and the de-sulfurization of oil on the other hand. The post measure refers to exhaust gas de-sulfurization, a process to remove SOx gases from flue gas combustion of oil and coal before releasing it from exhaust pipe. Exhaust gas de-sulfurization, however, can only be applied to large-scale facilities because of economic viability. Therefore, use of low sulphur fuel should be encouraged. Government may also impose an additional tax on industries burning fuel with sulphur beyond certain limit. Nitrogen oxides are often referred to as NOx. NOx gases are emitted from high temperature combustion. When reacting with wet atmosphere, it forms acids. NOx is harmful to human health. It causes or worsens respiratory disease. Oxide of nitrogen also affects our nerve system. Our government should also set up NOx emission limit and monitor the quantity of NOx present in our atmosphere. Emission of particulates, solid particles of minute sizes, mainly generated from bad combustion of the engine is a major threat to Dhaka city dwellers. Particulate emission can be reduced to a minimum if engine components are maintained regularly and good quality fuel is used. Like other countries our government should also set up a standard for the quantity of the particulate that can be emitted from an engine. To get a fitness certificate the vehicles must prove their compliance with the emission standard set up by the government. We get fitness certificate without any such check by the BRTA. If we look at Malaysia, we can see vehicles are moving fast without producing smoke and honking horn can be seldom heard even from their busy street. All drivers are following traffic rules. Even if you go to a village in Malaysia, you will find they are burning their rubbish not allowing stinky gases to be produced from them. Roads are clean and huge natural greenery is taking care of citizen's health. Unnecessary burning of methane gas is not possible in most of the places, as the houses have no meter lessgas pipe connection. They use LP cylinder for cooking. Government must be aware of the consequences of not controlling pollution in our city, that may lead to a catastrophic damage to health of city dwellers. Let us take lesson from countries those are monitoring and taking care of their environment to save our children from the curse of pollution.
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