Air pollution in cities ‘up sharply over 45 years’

12May 2020
The Guardian
Air pollution in cities ‘up sharply over 45 years’

INCREASED air pollution in East Africa as revealed by decreasing visibility data over the last 45 years suggests that the sub-region is at high risk of pollution-related effects including diseases, a study says.

By Eldon Opiyo

The three cities — Addis Ababa in Ethiopia, Nairobi in Kenya and Kampala in Uganda — have undergone rapid population surge, with increased citywide fuel use and motorisation leading to a rise in a mixture of extremely small particles and liquid droplets into the air, thus aiding visibility loss, adds the study published in Environmental Research Letters last month.

According to a World Bank report, indoor use of solid fuels could lead to about 390,000 premature deaths in Africa annually while urban outdoor pollution is associated with 49,000 deaths, with Sub-Saharan Africa bearing the main burden.

But the study says that lack of good quality historic air pollution data in Sub-Saharan Africa makes it difficult to understand the current air quality situation and to estimate the future air quality trajectory.

The study, which used visibility as a proxy for air pollution used data on Addis Ababa, Nairobi and Kampala for 1974 to 2018, found significant visibility decrease, allowing researchers to estimate that air pollution increased by  62 per cent in Addis Ababa, 162 per cent in Kampala and 182 per cent Nairobi.

“Our study provides a much improved understanding of the past patterns of air pollution in East Africa using historical visibility and meteorological data,” says Ajit Singh, the study’s lead author and a postdoctoral research fellow in the School of Geography, Earth and Environmental Sciences at the UK-based University of Birmingham. “High rates of urbanisation and population growth can affect air quality in these cities.”

Researchers obtained meteorological data with a focus on the three cities using a tool called worldmet package for 1974 to 2018, and analysed the presence of a mixture of small particles and liquid droplets into the air over monthly, annual and seasonal cycles.

“Overall, a significant loss in East African visibility was observed since the 1970s where Nairobi shows the greatest loss (60 per cent) as compared to Kampala (56 per cent) and Addis Ababa (34 per cent),” the study says. Reduced visibility is an indicator of poor air quality and increased pollution.

Singh explains that the study focused on Kampala, Addis Ababa and Nairobi because they are the fastest growing cities in East Africa in terms of population, infrastructure, industrialisation and motorisation.

“This work greatly improves the data gap and provides a practical understanding of East African air quality trends and associated socio-economic consequences of poor air quality, which had never been attempted before,” Singh tells SciDev.Net.

Africa is not well-equipped with air quality monitoring because of the high cost of air quality monitoring equipment including their appropriate calibration and certification, he explains. He adds that unless systematic approaches with effective interventions are applied to control the air pollution in in East Africa, increased pollution levels resulting from fast developments processes and activities could occur. 

Charles Sebukeera, a research scientist and programme officer at the UN Environment Programme in Kenya, says that the study is important and is part of the efforts to build evidence on the increasing trend of air pollution in East Africa, which is attributable to increase in emissions resulting from human activities.

“Such analyses are needed to support [the work] of policymakers,” he adds.

But he explains that although the capacity to measure and deal with air quality monitoring is limited, there has been progress on air quality monitoring efforts in Kampala and Addis Ababa with publicly available data.

“At present there are few countries such as Uganda and Ethiopia with capacity to monitor [air quality]. It is also important to link the [air quality] monitoring to policy to reduce pollution,” he says, adding that key interventions to reduce air pollution from industries, households, cars and trucks include waste management and use of renewable energy.  

Sebukeera explains that because falling visibility is linked to development, there is need to strike a balance between economic development and reducing major air pollution by investing in clean technologies such as clean energy.