Reducing air pollution in cities

Dhaka,  Thu,  24 August 2017
Published : 20 Jun 2017, 21:26:08

Reducing air pollution in cities

Shishir Reza
Air pollution is now a matter of great concern in Bangladesh. Usually, the level of pollution is higher during daytime when most of economic activities take place. The level also varies for two reasons - weather conditions and certain types of economic activities taking place seasonally. 

According to World Health Organisation (2016), about 4.3 million people annually die due to air pollution caused by cooking fuels and 3 million people die due to outdoor pollution. Air pollution is one of the major environmental hazards being experienced by Bangladesh. The country is rated as extremely vulnerable in Environmental Vulnerable Index (EVI) with an overall score of 340. Besides, the World Bank has opined that reducing air pollution could save 3,500 lives from death while preventing Bangladesh's 230 million cases of respiratory disease annually. 

In 2016, the Yale University published a report on Environmental Performance Index (EPI) where SAARC countries were ranked : Bangladesh (174), India (141), Pakistan (144), Sri Lanka (108), Nepal (149), Bhutan (110), the Maldives (137), and Afghanistan (176) out of 180 countries. The position of India and Pakistan is evidently better than Bangladesh and even some African countries are more advanced despite their low per capita income and higher rates of poverty. 

About 98 per cent of cities in low and middle income countries including Bangladesh with more than 100,000 people violate the WHO air quality guidelines. Dhaka is considered one of such cities. Regarding urban air pollutants, the annual mean concentration of fine particulate matter (PM 2.5) since 2014 are 89.7 in Bangladesh, 73.6 in India, 64.1 in Afghanistan, 75.7 in Nepal, 39.0 in Bhutan, and 28.6 in Sri Lanka. 

In Bangladesh, Dhaka has the highest level of air pollution followed by Chittagong and Khulna. The airborne concentrations of sulphur dioxide, nitrous oxide and carbon dioxide have increased over the years. Smog becomes usual in the city during winter. Recently, the Department of Environment mentioned the sources of air pollution in Bangladesh's urban areas - 60 per cent pollutants from brick kilns, 18 per cent from road or soil dust, 10 per cent from vehicle smog, 10 per cent from burning of biomass and 10 per cent from construction activities.                                                                                                             

The construction of unplanned buildings and roads along with earth excavation for real estate can lead to soil erosion. Following rapid urbanisation, demand for bricks has increased as an outcome of Bangladesh's growing construction industry. The number of brickfields has also increased in the outskirts of urban areas to meet new demands. Air pollution from local brickfields enormously causes an emission of smoke, fly-ash, SO2 and dust carried by the wind in all directions. Situated conveniently near cities, such elements pollute both urban and rural environments.

A speedy growth of urban population is likely to pressurise the existing network of intra-urban and inter-urban roads and highways because the number and volume of vehicular traffic increase within the city or its suburbs at specific time of the day like rush hours. The number of motorised vehicles plying on Dhaka's streets was around 140,000 in 1995, 185,000 in 2000 and 290,000 in 2005 while it is about 385,000 at present. Two-stroke three-wheelers, diesel-powered trucks, outdated buses and various defective automobiles are responsible for emission of NOx, SOx, CO, particulates and hydrocarbons. 

Moreover, fuel used by automobiles spread CO, CO2, NOx and SO2. Bangladesh's petroleum refinery supplies diesel containing 1 per cent of sulphur per litre with the international standard being 0.2 per cent. Metal industries spread hydrogen sulphide, sulphur, fluorides, metal fumes (lead, zinc), smoke and particulates. Power plants are spreading fly-ash, CO, sulphur and nitrogen oxides and all trains spread lead, smoke, hydrocarbons, aldehydes and peroxides. 

Apparently, roadside digging for utilities services takes place all the year round without coordination. Once soil is removed and roads repaired after placing the sewerage lines, a new set of digging begins by BTCL or WASA. The concept of zoning does not exist in urban areas. Industries are often set up in residential areas with total disregard for safety of the residents. In Old Dhaka, various factories coexist with residential blocks - iron smelting, welding, plastic manufacturing and chemical industries. 

Furthermore, inhalation of carbon dioxide is injurious to health. It reduces blood's oxygen carrying capacity. A blood constituent called haemoglobin is a complex protein that carries oxygen to body cells. The oxygen attaches itself to the haemoglobin forming oxyhaemoglobin. Carbon monoxide combines with haemoglobin 200 times faster than oxygen. It forms carboxyhaemoglobin and reduces blood's oxygen carrying capacity. Consequently, cells are deprived of oxygen while exposure to 1-5 ppm of SO2 for an hour can be considered a physical threat. It is a pulmonary irritant that aggravates respiratory problems. 

The gas may also have carcinogenic effects while larger particulates may lodge in the nasal passage and easily dislodged. Smaller particles easily penetrate into lungs and are lodged there causing severe breathing problems. As particulate matters consist of chemical substances, they often lead to different types of diseases - black lung disease suffered by coal miners, pulmonary fibrosis by asbestos workers and emphysema suffered by city-dwellers. Some particulates are carcinogenic in nature and may cause cancer in humans. Nitrogen dioxide sometimes irritates the respiratory tracts - causing pulmonary fibrosis and emphysema once concentration level is elevated. Aldehydes irritate the eyes and respiratory tract.   

Thus, air pollution has emerged as a major environmental and health risk. With minimum levels of such pollution, Bangladesh can reduce health risks like stroke, heart disease, lung cancer and chronic or acute respiratory diseases. The lower the level of air pollution becomes the better people's cardiovascular and respiratory health. Moreover, indoor smoke is a serious health risk for some 3 billion people who cook and heat their homes with biomass fuels and coal. 

Outdoor air pollution in both cities and rural was estimated to cause 3.7 million premature deaths worldwide in 2012. Any failure to minimise air pollution would expose a significant portion of Bangladesh's labour force to serious health hazards.  

Air pollution can be reduced if policymakers start addressing such crisis. Fuels used by motor vehicles and industries contain chemicals polluting the air - sulphur in coal or diesel and tetraethyl lead in gasoline. Clean fuel like the low-pollutant Compressed Natural Gas (CNG) is a necessity. In Bangladesh, smoke and CO emission can be reduced by 80 per cent if CNG usage is ensured and catalytic converters are installed in automobiles to reduce emission of NOx, CO and hydrocarbons. 

The import of two-stroke three-wheelers should be stopped. A rigorous monitoring system must be developed to detect faulty vehicles plying the roads while violators should be penalised. The emission from industries must be controlled using upgraded technologies. Policies such as the setting of emission standards, emission charges and polluter payments can be applied to reduce industrial emission. Brick kilns should use clean fuels and relocate far away from densely-populated areas. 

The writer is an environmental analyst and an associate member of Bangladesh Economic Association (BEA).

Editor : A.H.M Moazzem Hossain
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