A team of researchers at the Kwame Nkrumah University of Science and Technology (KNUST) has detected persistent nitrogen dioxide (NO₂) pollution hotspots across the Greater Accra Region, raising new concerns about air quality and public health in Ghana’s most urbanised region.
Using satellite data rather than traditional ground-based monitors, the researchers tracked air pollution patterns over a five-year period, from 2019 to 2023, and found consistently high NO₂ concentrations in major urban and industrial areas, particularly around Tema’s Heavy Industrial Area.
Nitrogen dioxide is a harmful air pollutant mainly released from vehicle exhausts, industrial processes, power generation, and fuel combustion.
Prolonged exposure has been linked to respiratory illnesses, worsened asthma, and the formation of other dangerous pollutants such as ground-level ozone and fine particulate matter.
In Ghana, however, understanding the full scale of NO₂ pollution has been difficult due to the limited number of air-quality monitoring stations. This gap makes it challenging to identify pollution hotspots or design effective interventions.
To overcome this challenge, the KNUST research team turned to TROPOMI, a high-resolution satellite instrument that monitors air pollutants worldwide.
Using Google Earth Engine, a cloud-based geospatial analysis platform, the team analysed tropospheric NO₂ levels over Greater Accra.
Their findings revealed persistent NO₂ hotspots, with peak concentrations reaching 3.3 × 10¹⁵ molecules per square centimetre; levels associated with intense human activity.
The most affected areas were dense urban centres and industrial zones, where traffic congestion and large-scale industrial operations dominate.
Further analysis using Google Earth imagery revealed that the highest NO₂ concentrations coincided with areas containing refineries, factories, quarries, and other industrial facilities, especially within the Tema Industrial Area.
The research also uncovered clear seasonal variations in NO₂ levels. During the dry season (December to February), average NO₂ concentrations were significantly higher. In contrast, lower levels were observed during the rainy season (June to August).
According to the study, this pattern is influenced by a combination of factors such as increased emissions from human activity during the dry season and reduced atmospheric dispersion, as stable weather conditions allow pollutants to accumulate. During the rainy season, stronger winds and rainfall help disperse and wash pollutants out of the atmosphere.
Beyond identifying pollution hotspots, the researchers say the real value of the study lies in its methodology. By combining satellite observations with geospatial mapping tools, the approach offers a practical and cost-effective way to monitor air pollution in regions where ground-based data are scarce or unavailable.
The findings underscore the urgent need for targeted emission control measures, especially in industrial zones and high-traffic corridors. They also highlight the importance of expanding air-quality monitoring and integrating satellite data into Ghana’s environmental management strategies.
The research was published in the Multidisciplinary Digital Publishing Institute (MDPI) and was led by Dr. Prince Junior Asilevi, Lecturer and Research Scientist in Atmospheric and Environmental Physics/ Chemistry at the Department of Meteorology and Climate Science, KNUST. The study was conducted in collaboration with Dr. Patrick Boakye, Prof. Emmanuel Quansah, Alex Kwao Ablerdu, and Prof. William Ampomah.
By: Abena Serwaa Gyamfi
