Air pollution is
prevalent in cities and urban centers in developing
countries including sub-Saharan Africa, but ground monitoring data
on local pollution remain inadequate, hindering effective mitigation.
We employed low-cost sensing and measurement technologies to quantify
pollution levels based on particulate matter (PM2.5), NO2, and O3 over a 6 month period for selected urban
centers in three of the four macroregions in Uganda. PM2.5 diurnal profiles exhibited consistent patterns across all monitoring
locations with higher pollution levels manifesting from 18:00 to 00:00
and from 06:00 to 09:00; while the periods from 00:00 to 05:00 and
from 09:00 to 17:00 had the lowest levels. Daily PM2.5 varied
widely between 34 and 107 μg/m3 over a 7 day period,
well within unhealthy levels (55.5–150.4 μg/m3) for short-term exposure. The inconsistent daily trend are instructive
for multiple pollutant assessment to aid specific policy initiatives.
The results also show inverse relations between seasonal particulate
levels and precipitation, that is, R (correlation
coefficient) = −0.93 and −0.62 for Kampala and Wakiso, R = −0.49 and −0.44 for the Eastern region,
and R = −0.65 and −0.96 for the Western
region. NO2 monthly concentrations replicated PM2.5 spatial levels, whereas O3 exhibited inverse relations
probably due to a higher retention time in less-urbanized environments.
Both PM2.5 and NO2 correlated positively with
the resident population. Our findings show significant spatiotemporal
variations and exceedances of health guidelines by about 4–6
times across most study locations (with two exceptions) for longer-term
exposure. This paper demonstrably highlights the practicability and
potential of low-cost approaches for air quality monitoring, with
strong prospects for citizen science. This paper also provides novel
information regarding air pollution that is needed to improve control
strategies for reducing exposures.