The motor vehicle usage has increased tremendously in Dhaka, and like other metropolitan cities, Dhaka is also facing a pollution problem from emissions of carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM). Besides this, about 451 polluting industrial plants such as tanneries, textile mills, oil refineries, distilleries, fertilizers, paint manufacture, pulp and paper factory etc. discharge highly toxic effluent directly into the river in Dhaka. In a thickly populated area like Hazaribagh, there are about 160 tanneries discharging 28 to 35 liters of waste effluent for each kilogram of hide processed which contains toxic heavy metals like chromium, arsenic, zinc etc. These run through open drains and fill the whole area with a putrid smell. About 1.3 million people in Dhaka depend on 6 x10 metric ton of wood and other non-conventional fuel in each year, which causes thick smoke from their cooking stoves. The purpose of this paper is to briefly survey the air pollution conditions in Dhaka city.
Air pollution is one of a variety of man made environmental disasters that are currently taking place all over the world. Air pollution may be defined as an atmospheric condition in which various substances are present at concentrations high enough above their normal ambient levels to produce a measurable effect on people, animals, vegetation, or materials. ‘Substances’ refers to any natural or man made chemical elements or compounds capable of being airborne. These may exist in the atmosphere as gases, liquid drops, or solid particles. It includes any substance whether noxious or benign; however, the term ‘measurable effect’ generally restricts attention to those substances that cause undesirable effects. Air quality has deteriorated both due to human activities, and natural phenomenon such as windblown dust particles etc.
There are two major sources of air pollution in Bangladesh, vehicular emissions and industrial emissions. However, these are mainly concentrated in the cities. Recently, air pollution has received priority among environmental issues in Asia, as well as in other parts of the world. Exposure to air pollution is the main environmental threat to human health in many towns and cities. Particulate emission is mainly responsible for increased death rate and respiratory problems for the urban population. This problem is acute in Dhaka being the capital of the country and also the hub of commercial activity. Dhaka is a major, cultural, and manufacturing center. The common types of industries in and around the periphery of Dhaka are ready-made garment manufacturing, jute, tanneries, textile, tea processing, fertilizer, cement, paper and pulp, chemicals and pesticides, food and sugar, pharmaceuticals, petroleum refinery, distillery, rubber, plastics, and brick manufacturing, assembling buses, trucks, and motorcycles, assembling radios and televisions. Air of Dhaka is being polluted day by day very badly. The other urban areas i.e. Chittagong, Khulna, Bogra and Rajshahi have much lesser health problem related to urban air pollution. The ambient atmospheric conditions have progressively deteriorated due to the unprecedented growth in numbers of motor vehicles, and continuous housing and industrial development.
Contamination in the atmosphere caused by the discharge, accidental or deliberates of a wide range of toxic substances. Often the amount of the released substance is relatively high in a certain locality, so the harmful effects are more noticeable. The major sources of air pollution are transportation engines, power and heat generation, industrial processes and the burning of solid waste. A new source of air pollution is an increasing 'hole' in the ozone layer in the atmosphere above Antarctica, coupled with growing evidence of global ozone depletion. Air pollution has also long been known to have an adverse effect on human beings, plants, livestock and aquatic ecosystem through acid rain.