Quantifying Residential Particulate Pollution and Human Exposure in Ibadan, Nigeria, Using Low-Cost Sensors

Abstract Exposure to fine particulate matter (PM 2.5 ) pollution, both outdoors and indoors poses a significant health burden in Africa, where concentrations are often high, but there are limited measurements. Two types of low-cost sensors were used during two distinct measurement phases conducted in Ibadan, Nigeria. In Phase I, indoor and outdoor PM 2.5 concentrations were measured for a two-week period in twelve households using a total of twenty-four Atmotube PRO sensors. Phase II consisted of a seven-month extended monitoring study conducted in two households (each equipped with one indoor and one outdoor sensor) and a school (1 sensor only) using five PurpleAir sensors. Across the twelve households in Phase I, daily median PM₂.₅ concentrations ranged from 12.0 to 18.0 µgm −3 indoors, and from 12.2 to 20.0 µgm −3 outdoors. The overall PM 2.5 indoor-outdoor (I/O) median ratio was 0.9 indicating that outdoor levels were typically slightly higher than indoors. In January (the dry harmattan season), daily median PM 2.5 concentrations were 98.0 µgm −3 indoors and 109.3 µgm −3 outdoors. In contrast, lower PM 2.5 concentrations of 21.4 µgm −3 indoors and 24.5 µgm −3 outdoors were recorded in May, a rainy season. In Phase II, we find that a substantial part (~ 90%) of PM 2.5 concentrations can be explained by variance in the outdoor concentrations. There was exceedance of WHO interim target IT-1 of 75 µgm −3 for PM 2.5 during the dry harmattan season. The findings highlight the need for continuous air quality monitoring infrastructure to track pollutant trends and offering insights for future research. Graphical Abstract