One third of premature deaths attributed to air pollution in Bangladesh are caused by fossil fuel, the figure being the second highest in the world, an international study has found.
It used air pollution data dating back to 2012. A total of 692,081 people died of air pollution-related diseases in Bangladesh in that year. Of them, 252,927 (36%) died due to the presence of fossil fuel particulates in the air.
Air pollution caused by the burning of fossil fuel (coal, oil petroleum and natural gas) is responsible for one in five deaths worldwide, the study noted. This means Bangladesh's figures are almost double the world average.
The researchers estimated the burning of fossil fuel in different sectors, including power, industry, and all kinds of transportation in the study.
The findings of the study – conducted by Harvard University in collaboration with the University of Birmingham, the University of Leicester, and University College London – were unveiled today (Tuesday).
China topped the top 10 table with 40.2% of deaths attributed to fossil fuel-driven air pollution while India was in third position with 30.7%. South Korea and North Korea were placed in fourth and fifth positions respectively.
The latest Global Burden of Disease Study put the number of deaths in Bangladesh caused by all outdoor and indoor airborne particulates, including dust and smoke from wildfires and agricultural burns, at 173,500 in 2019.
It was the largest and most comprehensive study on the causes of global mortality jointly conducted by the US-based Health Effects Institute and the Institute for Health Metrics and Evaluation.
But the Harvard study said 252,927 people died in Bangladesh only from fossil fuel in 2012. It excluded the death tolls of children under 14. Moreover, the researchers preferred using the 2012 data even though data for 2018-2019 were available.
Asked why they had used 2012 data, the research team told The Business Standard in an email reply that global meteorological conditions can affect air pollution estimates, and the El Niño weather pattern in particular can worsen or improve air pollution.
The study used 2012 data as El Niño was in a neutral phase that year, meaning it did not affect air pollution levels at the time, they said.
"If it had used data from another year, the estimates of air pollution mortality might have been higher or lower because of El Niño. So, it was an intentional choice to use 2012 data to prove the reliability of the findings, not because 2018 data was not available."
What is El Niño?
El Niño is an irregularly occurring and complex series of climatic changes affecting the equatorial Pacific region and beyond every few years. Its effects include the reversal of wind patterns across the Pacific, drought in Australasia and unseasonal heavy rain in South America.
Dr Ahmed Kamruzzaman Majumder, professor and chairman of the Department of Environmental Science at Stamford University, told The Business Standard the Harvard study findings were reliable as the university had used the latest model and technological intervention. But the numbers might slightly differ as immune systems of human beings varied from one country to another.
"The death tolls in air pollution caused by both fossil fuel and other sources in Bangladesh are very high. All these deaths occur due to human activities. If we can reduce the burning of fossil fuel as well as other sources of air pollution, we can prevent these unwanted deaths."
"For example, when we banned two stroke three-wheelers from Dhaka's streets, air pollution was reduced by 40%. Similarly, if we can stop fossil fuel burning in different industries, we will be able to reduce the number of those deaths significantly," explained Kamruzzaman.
He said air quality had improved by 40-50% during the first three months of the Covid-19 outbreak due to the lack of human intervention in nature.
Renewable energy is the ultimate solution to minimise fossil fuel-related deaths, he added.
In 2014, fossil fuel energy consumption in Bangladesh increased to 73.8% from 54.4% in 1995, growing at an average annual rate of 1.62%
Method used in study
Satellite and surface observations cannot tell the difference between particles from fossil fuel emissions and those from dust, wildfire smoke or other sources. With satellite data, one can only see pieces of the puzzle. Thus, there can be a gap in the data.
To overcome this challenge, the Harvard researchers turned to GEOS-Chem, a global 3-D model of atmospheric chemistry. GEOS-Chem has high spatial resolution, can segment the globe into a grid with boxes as small as 50km x 60km and look at pollution levels in each box individually.
Rather than relying on averages spread across large regions, researchers wanted to map where pollution was taking place and where people lived so that they could know more exactly what people were breathing.
To model PM2.5 generated by fossil fuel combustion, the researchers plugged into GEOS-Chem estimates of emissions from multiple sectors and simulated the detailed oxidant-aerosol chemistry driven by meteorology from the National Aeronautics and Space Administration Global Modelling and Assimilation Office.
Once they had the concentration of outdoor fossil fuel PM2.5 for each grid box, they needed to figure out how those levels impacted human health.
Harvard TH Chan School of Public Health developed a new risk assessment model that linked the concentration levels of particulates from fossil fuel emissions to health outcomes.
This, say the researchers, is the reason why the findings are more accurate than previous research.