Air pollution - severe environmental hazard

Humans probably first experienced harm from air pollution when they built fires in poorly ventilated caves. Since then we have gone on to pollute more of the earth's surface. Until recently, environmental pollution problems have been local and minor because of the Earth's own ability to absorb and purify minor quantities of pollutants. The industrialization of society, the introduction of motorized vehicles, and the explosion of the population are factors contributing toward the growing air pollution problem.

Air is indispensable for the survival of all living organisms on earth, including human beings. It is even more important than water - without water a person can survive for days, but without air no more than a couple of minutes.

Air pollution is one of a variety of manmade environmental disasters that are currently taking place all over the world. It is an atmospheric condition in which various natural or manmade chemical elements or compounds, capable of being airborne, are present at concentrations high enough above their normal ambient levels to produce a measurable effect on people, animals, vegetation, or materials.

These may exist in the atmosphere as gases, liquid drops, or solid particles. 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, the capital of the country and also the hub of commercial activity. The other urban areas i.e. Chittagong, Khulna, Bogra and Rajshahi have much lesser health problems related to urban air pollution.

Bangladesh is one of the least developed agrarian nations in the world. Since it's inception in 1971, there has been some growth in the industrial sector. Industries are mainly concentrated in major urban areas like Dhaka, the seaport cities like Chittagong and Khulna, the inland port city Narayanganj, and other divisional towns. Naturally, the air pollution problem is more acute in these areas. Apart from unplanned industrial development in these areas, the severity of the pollution is increased mainly due to exhausts from two-stroke engine and diesel-run vehicles.

In the rural areas of Bangladesh, the air pollution problems have not yet become a point of concern. This is due to fewer motorized vehicles and industries in rural areas.

The primary air pollutants found in most urban areas are carbon monoxide, nitrogen oxides, sulfur oxides, hydrocarbons, and particulate matter (both solid and liquid). These pollutants are dispersed throughout the world's atmosphere in concentrations high enough to gradually cause serious health problems. Serious health problems can occur quickly when air pollutants are concentrated, such as when massive injections of sulfur dioxide and suspended particulate matter are emitted from different sources.

The principal sources of air pollution in the rural areas are brick kilns and cooking stoves. In rural areas, wood, coal, and bio-mass are used as sources of energy. During the monsoon, rural people cook inside their houses without adequate ventilation systems. This gives rise to severe indoor air pollution which brings health hazards, particularly for women and children.

There are two major sources of air pollution in Bangladesh, vehicular emissions and industrial emissions. These are mainly concentrated in the cities. Other than those there are numerous brick-making kilns operated seasonally, mainly in dry season all over Bangladesh. Almost all of these kilns use coal and wood as their prime sources of energy, resulting in the emission of particulate matter, oxides of sulfur, and volatile organic compounds. In addition to these usual sources of fuel, used rubber wheels of vehicles are also burnt, which emit black carbon and toxic gases. These are hazardous for health.

The major urban centers in the country are the metropolitan cities of Dhaka, Rajshahi, Khulna and Chittagong. Dhaka is one of the most densely populated cities in the world.

This is the center for the major economic and commercial activities. In the urban areas ambient air quality is dependent on many factors like air movement, traffic volume, congestion, emissions from motor vehicles, and resuspended dust particles. Various other activities related to the extremely high population density also result in severe air and other forms of pollution.

Aircrafts, railway engines, power plants, open burning incineration, solid waste disposal sites, and dust particles also contribute to air pollution. Dust pollution due to road diggings, constructions and other development activities further aggravate the air pollution situation in cities.

In order to accommodate the growing population, the construction of multi-storied buildings is increasing rapidly. Along with these buildings, the number of slums are also increasing. The tremendous pressure of population has made it almost impossible to maintain a clean environment in the capital city of Dhaka.

Industrial development is another source of air pollution. Industries in Bangladesh are situated mainly in major urban areas, particularly in Dhaka, Chittagong, and Khulna. So, air pollution is concentrated mainly in these cities. Brick-making kilns, of which the majority are of the conventional type, use coal and wood as their source of energy.

This is mainly due to the non availability of natural gas in most parts of Bangladesh. The air pollution from these kilns is not only due to the type of fuel used, but also due to the thermal inefficiencies of the conventional kilns. This causes emissions like SOx, CO, particulate matters, and volatile organic compounds that deteriorate air quality. Another significant factor is that brick kilns are usually clustered near big cities in various parts of Bangladesh. Therefore, the parts of the city in the immediate vicinity of the clustered brick-fields have serious air pollution problems.

Children suffer more from air pollution in the cities. Most of the children in the cities of Bangladesh are suffering from respiratory problem. Because children breathe more air relative to their body weight and lung surface area than do adults. So, they also receive proportionately higher doses of air pollutants. They spend more time outdoors, often during midday and afternoons when pollutant levels are generally highest.

They are three times more active than adults while outdoor, significantly increasing their oxygen demand and consequently raising their breathing rates. Children often fail to recognize the significance of respiratory symptoms such as coughing, wheezing, and shortness of breath, and they frequently fail to move indoors of curtail exercise during air pollution episodes. Children tend to breathe more through the mouth than through the nose due to their increased physical exertion, thus reducing the effectiveness of one level of filtration. In addition, young children's small noses are easily blocked by congestion, constriction, or other illnesses.

Children at greatest risk from the effects of air pollution of sensitized respiratory systems, such as allergic or asthmatic, children who live near industrial pollution sources, areas of heavy traffic, or in homes with cigarette smokers, and children who lack adequate medical attention, nourishment, or sanitary living conditions.

In order to safeguard public health, biodiversity and ecosystems, sustainable environmental management needs to be ensured. As a part of country's environmental management air quality monitoring activities is going to be expanded to the major cities like Chittagong, Rajshahi, Khulna, Barisal, Sylhet and Narayangonj.

These cities will be brought under air quality monitoring network by 2007 by the Government of Bangladesh with support from the donor agencies. State of air pollution of these cities will be regularly communicated along with health advisory to the people to create more awareness through electronic and print media. A follow up project on Air Quality Management is undertaken with the financial assistance from the World Bank. It will also look into indoor air pollution, industrial process improvement with focus on change of technology of brick kilns, introduction of environment friendly public transport system and capacity building for air quality management.

(The Writer is a Senior Assistant Secretary of the Ministry of Environment and Forest.)