Abstract
Exposure to particulate air pollution is a major cause of mortality and morbidity worldwide. In developing countries, the combustion of solid fuels is widely used as a source of energy, and this process can produce exposure to harmful levels of particulate matter with diameters smaller than 2.5 microns (PM2.5). However, as countries develop, solid fuel may be replaced by centralized coal combustion, and vehicles burning diesel and gasoline may become common, changing the concentration and composition of PM2.5, which ultimately changes the population health effects. Therefore, there is a continuous need for in-situ monitoring of air pollution in developing nations, both to estimate human exposure and to monitor changes in air quality. In this study, we present measurements from a 5-week field experiment in Palapye, Botswana. We used a low-cost, highly portable instrument package to measure surface-based aerosol optical depth (AOD), real-time surface PM2.5 concentrations using a third-party optical sensor, and time-integrated PM2.5 concentration and composition by collecting PM2.5 onto Teflon filters. Furthermore, we employed other low-cost measurements of real-time black carbon and time-integrated ammonia to help interpret the observed PM2.5 composition and concentration information during the field experiment. We found that the average PM2.5 concentration (9.5 µg∙m−3) was below the World Health Organization (WHO) annual limit, and this concentration closely agrees with estimates from the Global Burden of Disease (GBD) report estimates for this region. Sulfate aerosol and carbonaceous aerosol, likely from coal combustion and biomass burning, respectively, were the main contributors to PM2.5 by mass (33% and 27% of total PM2.5 mass, respectively). While these observed concentrations were on average below WHO guidelines, we found that the measurement site experienced higher concentrations of aerosol during first half our measurement period (14.5 µg∙m−3), which is classified as “moderately unhealthy” according to the WHO standard.
Highlights
Exposure to particulate air pollution with aerodynamic diameters smaller than 2.5 μm (PM2.5 ) is linked with premature mortality [1] and morbidity [2], and is currently one of the most important causes of premature mortality in developing and rapidly industrializing nations [3]
We present the PM2.5 time series from the AMOD devices in Figure 2: the real-time Plantower observations are denoted by the points, distinguishing between the two AMOD instruments; the filter observations are denoting by the horizontal black lines with the width representing the duration of the measurement period
We used low-cost AMOD measurement systems that are capable of collecting PM2.5 samples on Teflon filters, along with surface-based aerosol optical depth (AOD), and real-time PM2.5 concentrations, all in a portable, low-cost system
Summary
Exposure to particulate air pollution with aerodynamic diameters smaller than 2.5 μm (PM2.5 ) is linked with premature mortality [1] and morbidity [2], and is currently one of the most important causes of premature mortality in developing and rapidly industrializing nations [3]. State-of-the-art methods for quantifying the global health burden of air pollution use remote sensing tools and atmospheric chemical transport models (CTMs) fused with in situ measurements to produce estimates of pollutant concentrations in regions where surface measurements are sparse [4,5]. Estimates of emissions from domestic biomass burning vary [9,10], leading to uncertainty in the representation of these sources in regional and global CTMs, which propagates to estimates of disease burden [7]. As sub-saharan African nations undergo economic development, the important regional sources of aerosols will change, as coal combustion for electricity production replaces domestic solid fuel use, and fossil fuel vehicles become more common [11]. “sub-saharan Africa” refers to a large collection of countries with different climate regions and cultures, spanning an area three times the size of the United States
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