Observed and Modeled Seasonal Air Quality and Respiratory Health in Senegal During 2015 and 2016

Abstract

In this work, we use existing particulate matter (PM) data from Dakar, Senegal, satellite aerosol optical depth (AOD) and the Weather Research and Forecasting (WRF) model to evaluate the role of dust transport from the Sahara and PM concentrations and exposure into other administrative districts of Senegal during 2015 and 2016. We also use data from the Ministry of Health to examine spatial and temporal patterns of acute respiratory infections, asthma, bronchitis, and tuberculosis across Senegal with an emphasis on Northern Hemisphere winter December-February, when air quality is poor, and June-August when there is an improvement in air quality. Measurements in Dakar, Senegal, suggest hazardous PM 10 concentrations associated with Saharan dust storms but lower PM 10 concentrations during the summer. The WRF dust simulations show a similar temporal pattern to the observations in Dakar, Senegal, with notable biases. However, the WRF model suggests that the highest dust concentrations are found across the northern half of Senegal during the winter season where there are no currently PM measurements. Health data during 2015-2016 show the highest prevalence of asthma and bronchitis in Dakar, Senegal, suggesting that other sources of air pollution are important. Acute respiratory infection is prevalent throughout the country with the high prevalence found in rural zones, for children between 12 and 59 months. All measures including real-time monitoring, air quality forecast, and communication should be used to protect the public from potentially hazardous environmental conditions during the winter season. Plain Language SummaryAir pollution is a leading cause of respiratory and cardiovascular disease and may be responsible for a significant fraction of infant mortality in West Africa. We examine observations and simulations of PM 10 and PM 2.5 concentrations using the Weather Research and Forecasting model during 2015 and 2016 in Dakar, Senegal, and the entire country. We also examine monthly and trimester patterns of asthma, bronchitis, acute respiratory infection, and tuberculosis cases across Senegal. Observations from Senegal show that monthly PM 10 and PM 2.5 concentrations are unhealthy from December through March but improve during the summer months. Saharan dust aerosols, which are transported into Senegal are responsible for the poor air quality through attribution studies using the Weather Research and Forecasting model. We also find the largest numbers of cases of asthma and bronchitis in Dakar, suggesting that urban sources contribute to poor air quality. However, these cases occur during the summer season when air quality is improved. Acute respiratory infection is a public concern in Senegal with the highest values occurring away from the capital city.

A Scoping Review on Air Quality Monitoring, Policy and Health in West African Cities

“…However, Dakar's CGQA website only mentions five active air quality monitoring sites, excluding the one in Guédiaway [48]. Another study on Dakar combined air quality monitoring data, data from the Ministry of Health, models, and also considered seasonal variability of Saharan dust influence in order to examine patterns of respiratory conditions, such as asthma, bronchitis, and tuberculosis [9]. They found a higher prevalence of respiratory conditions in Dakar versus other parts of the country, which suggested the strong influence of anthropogenic air pollution.…”

“…As the urban population increases, especially in low-and middle-income countries (LMICs), an increasing amount of people are becoming susceptible to suffering from these health effects [8]. A study that was carried out in Senegal, for example, identified the links between poor air quality and conditions, like asthma and bronchitis, especially in urban regions [9]. Air pollution also leads to millions of preventable deaths each year-4.2 million in 2016-90% of which are concentrated in LMICs [2,10].…”

“…In the countries where legislations have been passed, enforcement is often weak, as well as coordination between relevant government sectors. For example, Toure et al [9] showed how coordinating data from the Ministry of the Environment and the Ministry of Health would allow for better understanding the extent of the influence of air quality on respiratory conditions in Senegal, yet it is unknown whether or not such coordination occurs at the government level for Senegal or for other ECOWAS countries. Insufficient air quality data means that many national and local governments only have partial knowledge of emissions sources, concentrations, and evolution trends.…”

Air Quality Impacts at an E‐Waste Site in Ghana Using Flexible, Moderate‐Cost and Quality‐Assured Measurements

“…The Harmattan season is highly variable from year to year and characterized by dry and hazy conditions and little rainfall, which allows widespread entrainment and dispersal of fine and coarse fraction dust from the Sahara Desert across western Africa (Awadzi & Breuning-Madsen, 2009;Lanzerstorfer, 2017;Toure et al, 2019). In Ghana, these dusts usually originate in intense dust storms ("haboobs") caused by the Bodélé depression occurring between Tibesti and Lake Chad (K. Sunnu et al, 2018;Naidja et al, 2018).…”

“…In northern Ghana, the season is dominated by the NE Harmattan winds, and by SW monsoon winds in southern Ghana, although instabilities in the ITCZ can lead to NE Harmattan winds in the south (Awadzi & Breuning-Madsen, 2009). While only surface PM measurements are directly relevant to community exposures, satellite estimates of AOD and other optical properties, and surface sun photometer estimates of AOD can indicate the potential presence of Harmattan dusts (Toure et al, 2019). These indicators have limitations: the column integrated measures are estimated only during daytime and when clouds do not obscure the sun, MODIS satellite coverage is incomplete at the equator (often the study area is excluded), and most importantly, the relationship between AOD and surface PM concentrations is not direct.…”