A Network of Field-Calibrated Low-Cost Sensor Measurements of PM(2.5) in Lomé, Togo, Over One to Two Years

[Image: see text] Air pollution is a leading cause of global premature mortality and is especially prevalent in many low- and middle-income countries (LMICs). In sub-Saharan Africa, preliminary monitoring networks, satellite retrievals of air-quality-relevant species, and air quality models show ambient fine particulate matter (PM(2.5)) concentrations that far exceed the World Health Organization guidelines, yet many areas remain largely unmonitored and understudied. Deploying a network of five low-cost PurpleAir PM(2.5) monitors over 2 years (2019–2021), we present the first multiyear ambient air pollution monitoring data results from Lomé, Togo, a major West African coastal city with a population of about 1.4 million people. The full-study time period network-wide mean measured daily PM(2.5) concentration is 23.5 μg m(–3) m(–3). The strong regional influence of the dry and dusty Harmattan wind increases the local average PM(2.5) concentration by up to 58% during December through February, but the diurnal and weekly trends in PM(2.5) are largely controlled by local influences. At all sites, more than 87% of measured days exceeded the new WHO Daily PM(2.5) guidelines; these first measurements highlight the need for air quality improvement in a rapidly growing urban metropolis.