Spatial Extent and Distribution of Ambient Airborne Particulate Matter (PM2.5) in Selected Land Use Sites in Nairobi, Kenya

Abstract

Air pollution is one of the most important environmental and public health concerns worldwide. Urban air pollution has been increasing since the industrial revolution due to rapid industrialization, mushrooming of cities, and greater dependence on fossil fuels in urban centers. Particulate matter (PM) is considered to be one of the main aerosol pollutants that causes a significant adverse impact on human health. Low-cost air quality sensors have attracted attention recently to curb the lack of air quality data which is essential in assessing the health impacts of air pollutants and evaluating land use policies. This is mainly due to their lower cost in comparison to the conventional methods. The aim of this study was to assess the spatial extent and distribution of ambient airborne particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) in Nairobi City County. Seven sites were selected for monitoring based on the land use type: high- and low-density residential, industrial, agricultural, commercial, road transport, and forest reserve areas. Calibrated low-cost sensors and cyclone samplers were used to monitor PM2.5 concentration levels and gravimetric measurements for elemental composition of PM2.5, respectively. The sensor percentage accuracy for calibration ranged from 81.47% to 98.60%. The highest 24-hour average concentration of PM2.5 was observed in Viwandani, an industrial area (111.87 μg/m³), and the lowest concentration at Karura (21.25 μg/m³), a forested area. The results showed a daily variation in PM2.5 concentration levels with the peaks occurring in the morning and the evening due to variation in anthropogenic activities and the depth of the atmospheric boundary layer. Therefore, the study suggests that residents in different selected land use sites are exposed to varying levels of PM2.5 pollution on a regular basis, hence increasing the potential of causing long-term health effects.

Climate-Sensitive Health Outcomes in Kenya: A Scoping Review of Environmental Exposures and Health Outcomes Research, 2000 – 2023

“…The largest subtopic of this category assessed respondent’s awareness and perceptions of CCH (n=51), followed by exposure to air and water pollution, with 36 and 22 articles respectively. Demographic and social determinants were frequent elements to these studies, especially air pollutant exposure studies in informal settlements [21, 22] and studies on gender vulnerabilities of indoor air pollution [23–25]. Gendered access or lack thereof was identified in educational attainment and accessibility to health facilities [26, 27].…”

Turbulent Diffusion Effect on PM2.5 Concentration above an Urban Canopy

“…( 12) and ( 13) used to fit the data. y = a*x^b in unstable conditions (12) y = c + d*x in stable conditions (13) Where a, b, c, and d, are empirical constants based on observed data. Also, we used the parameter R-squared (R 2 ) to describe how much variance in the relationship between two (or more) variables has been taken into consideration.…”

“…Therefore, more accurate representations of turbulent diffusion are crucial for accurately simulating PM 2.5 concentrations in mode conversion and various meteorological conditions. Numerous studies looking at the processes that cause severe haze have been carried out recently [12] [13]. A number of factors, including gasparticle aerosol physicochemical processes, regional transportation, pollutant emissions, and PM 2.5 behavior in the boundary layer, affect the amount of PM 2.5 in the atmosphere [14].…”

Patterns and drivers of maternal personal exposure to PM2.5 in informal settlements in Nairobi, Kenya

“…A recent study with several PM 2.5 ambient installations across Nairobi reported 24 hours mean PM 2.5 concentration ranging from 22 to 112 µg m −3 , with one of the sites close to informal settlements (Mathare) measured at 50 µg m −3 . 16 Another study in 2017 documented somewhat lower, almost year-long ambient concentrations near informal settlements by Kibera and Viwandani of 23 and 21 µg m −3 , respectively. 17…”

“…A recent study with several PM 2.5 ambient installations across Nairobi reported 24 hours mean PM 2.5 concentration ranging from 22 to 112 mg m −3 , with one of the sites close to informal settlements (Mathare) measured at 50 mg m −3 . 16 Another study in 2017 documented somewhat lower, almost yearlong ambient concentrations near informal settlements by Kibera and Viwandani of 23 and 21 mg m −3 , respectively. 17 These studies have helped characterize the relatively high ambient PM 2.5 concentrations in Nairobi, as well as potential associations with land-use zones and pollution sources, such as vehicle emissions; however, they have not provided granular exposure estimates for subpopulations which may be especially impacted by air quality, such as expecting mothers in informal settlements, nor analyses of specic drivers of those exposure estimates.…”