GAW Report No. 205 - IGAC Project

CHAPTER 2 - AFRICAAs shown in Figure 10, ultra fine and fine PM induce higher biological effects (GM-CSFcytokines) as compared to coarse particles, whatever the sites. Bamako aerosol can bedistinguished by an impressive biological reactivity associated to local sources, since less reactivewhen diluted by external input such as dusts. This reactivity is stronger in Bamako than in Dakar.Considering aerosol chemical speciation in the two cities, aerosol biological responses seem to beclosely related to organic compound contents [Val et al., 2013].Figure 10 - GM-CSF cytokine concentrations as a function of aerosol size classes for the reference sample (Ctr), andBamako (BK1 and BK2) and Dakar samples. Different doses (1-5 et 10 g/cm 2 ) have been tested [Val et al., 2012]Other in-vitro studies dealing with air pollution effects possibly involved in lung toxicity inepithelium cells have been recently conducted in Abidjan for urban, industrial and rural sites onA549 cells and in Dakar for traffic and rural sites on BEAS-2B cells [Kouassi et al., 2010; Dieme etal., 2012]. Both studies have confirmed that both anthropogenic transition metals (Fe, Al, Al, Pb,Mn, Zn) and organic compounds (PAH) are involved in a time and dose dependent secretion ofinflammatory mediators and ensuing oxidative damages. Note that high levels of reactive oxygenspecies have been measured at Abidjan sites, not in Dakar.Finally, in the frame of POLCA (O. Koita, pers. com.), atmospheric bacterial population hasbeen studied in Bamako for a six-month period (57% Bacillus against 34% Cocci). The presence ofthese bacteria is an important factor for the prevalence and incidence of respiratory andcardiovascular diseases in Bamako. Note that dust-carrying bacteria are generally associated withmeningitis epidemics in the Sahelian belt. Indeed, meningitis outbreaks typically occur a few daysafter dust events: mechanistically, combination of lung system damage due to atmosphericpollution, dust vectors and bacteria could jointly act in developing epidemics. Many studies are stillon going to decipher such occurrences.2.2.5 ConclusionAs mentioned in the present chapter, air pollution and health is a real joint problem in WestAfrican capitals. The main sources of emissions are linked to traffic, domestic fuel combustion andwaste burning. The importance of industrial activities has been pointed out in South Africa only.The main emissions sources are controlled with only a few regulations (e.g. fuel desulfurization inSenegal, lead decrease in Nigeria). The situation is expected to rapidly deteriorate in the absenceof any further actions. Moreover, political conditions in West Africa will result again and again inpopulation migration and urbanization. It is now urgent for research studies to focus on integratedprojects combining emissions, air quality, health studies (epidemiological monitoring, toxicology,hospitalizations), acid deposition and impacts on soil and water resources together with local andregional climate change studies to provide possible emission mitigation options resulting in positiveimpacts.40