Among the top 10 causes of death in Bangladesh 5 are related to air pollution, experts said. The situation is more serious than we can imagine. The pollution of air is a global threat. According to World Health Organisation (WHO), after a worldwide collection of data, it has been found that only 12 per cent people live in the cities that are within the WHO's guidelines. WHO found by its analysis of the particulate matter, that about 90 per cent of human around the globe are exposed to polluted air. This was correlated to 7 million premature deaths in the year 2016. Out of this 7 million, Southeast Asia accounts for 2.4 million. On 18th March this year, Dhaka was ranked as the fourth most polluted city in the world with an index value of 195 and Kathmandu was the first, with 208 indexes. On 11th of March also this year, according to the same index, Dhaka became the most polluted city with the index value of 339. They say the level of air pollution may vary from hours to days.
WHO has addressed Dhaka as the third most polluted city in terms of air pollution. This data collection was done for megacities, around the world, with a population of 14 million or more. On 23rd February, Dhaka became number one, with 339 values in the US Air Quality Index (AQI). Lahore, Pakistan and Delhi, India were just lagging behind Dhaka. On 17th February, among all the cities worldwide, which had low air quality, Dhaka ranked second. Delhi tops the list, while Karachi stands third and Beijing fourth. All in all, it can be summarised that in the recent years, Dhaka has been in the top five of the list of world's most air-polluted cities. Since 1990 to 2015 many of the studies and research proves that Bangladesh and its neighbour India have the steepest increase in air pollution level.Bangladesh’s Department of Environment reveals that the pollution is much less during the monsoon. But why the fresh and clean air, that the previous generation used to breathe, has changed so much? Why has it becomes so harmful? What did they do to keep the air fresh and healthy? Unplanned brick kilns, faulty vehicles, especially that run on diesel, dust from roads and construction sites and poisonous gases and fumes from the industrial factories – all make contribution to polluting the air. At present more than 8,000 traditional brick kilns are actively working in the whole of Bangladesh. Burning of agricultural residues in the open air, coal-fired power plants and solid fuel use are major contributors too. Not only outside but air indoors can also be polluted. The paint or coating the modern houses contains asbestos, formaldehyde, etc. The wood stoves, space heaters and fireplace all release carbon monoxide and nitrogen dioxide. All of these chemicals and their gases are very harmful for the respiratory tract and system. PM 2.5 is an air pollutant with particles' diameter less than 2.5 micrometre. Long term exposure to these fine particulate matters contributed to 4.2 million premature deaths across the globe.
The effects of air pollution are uncountable. Different pollutants harm in different ways. High levels of PM 2.5 exposure could accelerate bone density loss and thus the risk of fracture, for people with less physical exercise. Data analysis and research have shown high levels of PM10 (particulate matter with less than 10 microns in diameter) increase the risk of abnormal foetal growth. Similarly, exposure to nitrogen dioxide pollution, pollutants from traffic and cigarette smoking and both coarse and fine particles affect the cognitive function of children by changing the brain structure. Other health issues caused by the polluted air are respiratory tract infection, irritation, allergies, headache, asthma, high blood pressure, heart ailments and even cancer.
Pollution of air has also some environmental impacts, other than on humans. The release of nitrogen oxides and sulphur oxides in the air, invites acid rain. Air pollution also causes eutrophication which leads to death of fish and plant life, and ground-level ozone and haze. Haze decreases visibility since when sunlight and pollution particles are mixed together, they become foggy. Ground-level ozone leads to reduction in crop and tree productivity.
Air pollution effects wildlife too. The toxic pollutants in the air force species to move and change their habitat. The pollutants can deposit on surface water and affect other water bodies.
Some basic solutions that can be thought of are - use the public mode of transport as much as possible and also encouraging and making children habituated to using public transport; conservation of energy can also be done by saving electricity and thus preventing more fossil fuels to burn and trying to recycle any material mechanically, rather than using energy for it. Adaptation of energy saving devices can also help a great deal. The use of clean energy such as sunrays and wind and geothermal energy must also be promoted worldwide.
For the assessment of air quality, there are generally two ways. The first one is U.S. Nation Ambient Air Quality Standards and E. U. Air Quality Directive. These classes of standards provide the values for the maximum atmospheric concentration for specific pollutants. Environmental agencies across the globe made rules and regulations that lead to achieving the target levels. The North American Air Quality Index, which is the second class, is made in the form of scale which contains numerous magnitudes of many different pollutants ranges and advocates risks to that people. The Parliament has enacted the Environmental Conservation Act 1995 and the Environment Conservation Rules 1997. Under the rules, the standards for Vehicular Exhaust Emission, Ambient Air Quality, Gaseous Emission or Projects Standards and the River Transport - have all been set. The Act 1995 also consists of regulations and rules which aid in the protection of environmental health and control of environmental pollution.Despite of many laws and regulations and set of standards, the level of air pollution in Dhaka keeps rising. Across the globe, 95 per cent of people are breathing unhealthy air and the poorest nations suffer the most. Our population rates and the need for development makes us more vulnerable to many environmental hazards especially air pollution. If the level of the pollutants in the air keeps increasing at the rate they are, the future is more horrific than we can imagine. The governments, scientists, experts and the common men around the world all will have to come up with effective solutions soon.
The writers are associated with teaching and research in the Department of Environmental Science at Stamford University Bangladesh. E-mail: firstname.lastname@example.org)-