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

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) 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 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 concentration is 23.5 μg m m. The strong regional influence of the dry and dusty Harmattan wind increases the local average PM concentration by up to 58% during December through February, but the diurnal and weekly trends in PM are largely controlled by local influences. At all sites, more than 87% of measured days exceeded the new WHO Daily PM guidelines; these first measurements highlight the need for air quality improvement in a rapidly growing urban metropolis.