Air pollution in big cities of Bangladesh, particularly Dhaka and Chittagong, is an ongoing concern for all. Only recently, WHO ranked Dhaka's air quality as the third worst, behind New Delhi and Cairo, in a study of megacities with a population of 14 million or more.
Not only the poor but the urban middle class too breathe the foul air, when they have to go to work or want to run errands by travelling on foot, in a rickshaw, or other means of public transportation. People in some areas of Dhaka suffer more than others. As an example, if you travel through any neighbourhood of Dhaka, be it Mirpur, Agargaon, Badda or Uttara, you see areas which have been dug up for development work and construction materials which are exposed to the elements and cause environmental hazards. And if you are stuck in traffic, God forbid, in that case, in addition to time spent fretting about the delay and the noise, you also need to cover your nose to keep out the smell of diesel and petrocarbons as well as dust.
The ill effects of air pollution are pretty well known. As scientists researching its health effects on human beings study more diligently using longitudinal data that was previously not accessible, we learn more about the pernicious effects of different types of air pollutants. With newer scientific methods available now, the linkages between air pollution and health are being discovered and established with a greater degree of certainty.
It was known for a long time that air pollution causes many types of respiratory diseases, including asthma and emphysema. The causal link between SPM and heart attacks and strokes has also come under scrutiny, and now is being systematically analysed and proven. However, very few epidemiological studies have addressed the association between air pollution and cognition in older adults who breathed polluted air.
In a 2014 study, however, in the prestigious scientific journal Epidemiology, it was found that traffic-related pollution in greater London was associated with declining cognitive functions over time among study participants who had an average age of 66. In a more recent study, researchers from US and China found that long-term exposure to air pollution negatively impacts the brain. This result is based on the performance in nationwide math and word-recognition tests taken by a large sample of more than 25,000 people across 162 Chinese counties. This study “further amplifies the need to tackle air pollution now to protect the health of particularly the young and the elderly population,” said Heather Adair-Rohani of the WHO public health and environment unit.
Is there then a safe level for air pollutants that is internationally accepted? Bangladesh's Department of Environment (DoE) has embraced the Air Quality Index (AQI), a standard followed by the US Environmental Protection Agency. According to DoE, the range of 51 to 100 should be labelled as “moderate” and the 101 to 150 range should be labelled as “Caution for sensitive individuals” or one that indicates that there are likely to be consequences for children, particularly infants, the elderly with chronic lung or heart disease, and people who will be working hard in the ambient air. AQI of 151 to 200 is unhealthy for everyone, and over 200 is very unhealthy.
AQI in Bangladesh's cities has some seasonal variations. During the rainy season, from mid-April to mid-October, air quality is in the acceptable range thanks to the rain which washes away many of the pollutants, particularly SPM. During the rest of the year, i.e. the drier months when there is very little rainfall, the AQI at many points in Dhaka is found to be above 200, which is very unhealthy for those working outdoors, including construction workers, rickshaw-pullers, and road-side peddlers. The more vulnerable segment of city-dwellers—children, elderly and the sick—need to stay indoors in a “clean” environment. However, even for healthy adults, prolonged exertion requiring outdoor activity for several hours and involving heavy breathing or exertion should be discouraged. As an alternative, heavy exertion during certain hours of the day may be minimised to reduce possible side effects including unusual coughing, chest discomfort, wheezing, breathing difficulty, or unusual fatigue. The red signals include coughing and shortness of breath, eye and skin irritation, breathing problems and headache.
Let us consider a data point in time from last winter. On January 7, 2018, Dhaka's air pollution levels were at 330 which implies that the capital's air quality was “extremely unhealthy” and stayed that way for four consecutive days.
A report issued by the prestigious Royal College of Physicians (RCP) of UK cautions that air pollution may be associated with a much wider range of health conditions. Some health effects associated with air pollution are well recognised such as increase in hospital admissions and deaths from cardiovascular diseases, respiratory diseases and lung cancer. “We know that those with pre-existing cardiovascular and respiratory diseases and older people are particularly at risk. (This) report considers the evidence for effects of air pollution on diabetes and neurological disease, as well as how exposure during pregnancy may be associated with low birth weight and pre-term births.”
Air pollution and the SDGs are closely intertwined. While some have pointed out that air pollution was deemphasised in the SDGs, because there are no headline goals on air pollution, it is nonetheless mentioned in at least two targets—SDG 3 (health) and SDG 11 (cities). One of these critics, the Institute for Global Environmental Studies, concedes, “A broad perspective illustrates that air pollution is linked in principle to most of the SDGs.”
Another group of scientists led by Professor Andy Haines of the London School of Hygiene and Tropical Medicine detail how fighting air pollution can help achieve global development and climate goals in a paper called “Short-lived climate pollutant mitigation and the Sustainable Development Goals”. Dr Haines goes even further. “Many short-lived climate pollutant mitigation measures provide multiple near-term SDG benefits, which can generate an appetite for even greater action,” he said.
In one specific example, the authors describe how providing affordable, clean household energy such as modern stoves for poor households can reduce black carbon emissions during cooking and “improve household incomes (SDG 1), educational outcomes (SDG 4), access to modern energy (SDG 7), physical security and opportunities for women (SDG 5) and contribute to the development of sustainable cities and housing (SDG 11). At the same time, clean household energy technologies reduce exposure to household air pollution (SDG 3), and contribute to reduced climate warming (SDG 13) and deforestation (SDG 15).”
Dr Abdullah Shibli is an economist, and Senior Research Fellow, International Sustainable Development Institute (ISDI), a think-tank in Boston, USA. His new book Economic Crosscurrents will be published later this year.