title: Physico-chemical characterization of African urban aerosols (Bamako in Mali and Dakar in Senegal) and their toxic effects in human bronchial epithelial cells: description of a worrying situation.
abstract: BACKGROUND
  The involvement of particulate matter (PM) in cardiorespiratory diseases is now established in developed countries whereas in developing areas such as Africa with a high level of specific pollution, PM pollution and its effects are poorly studied. Our objective was to characterize the biological reactivity of urban African aerosols on human bronchial epithelial cells in relation to PM physico-chemical properties to identify toxic sources.
  
  
  METHODS
  Size-speciated aerosol chemical composition was analyzed in Bamako (BK, Mali, 2 samples with one having desert dust event BK1) and Dakar (DK; Senegal) for Ultrafine UF, Fine F and Coarse C PM. PM reactivity was studied in human bronchial epithelial cells investigating six biomarkers (oxidative stress responsive genes and pro-inflammatory cytokines).
  
  
  RESULTS
  PM mass concentrations were mainly distributed in coarse mode (60%) and were impressive in BK1 due to the desert dust event. BK2 and DK samples showed a high content of total carbon characteristic of urban areas. The DK sample had huge PAH quantities in bulk aerosol compared with BK that had more water soluble organic carbon and metals. Whatever the site, UF and F PM triggered the mRNA expression of the different biomarkers whereas coarse PM had little or no effect. The GM-CSF biomarker was the most discriminating and showed the strongest pro-inflammatory effect of BK2 PM. The analysis of gene expression signature and of their correlation with main PM compounds revealed that PM-induced responses are mainly related to organic compounds. The toxicity of African aerosols is carried by the finest PM as with Parisian aerosols, but when considering PM mass concentrations, the African population is more highly exposed to toxic particulate pollution than French population. Regarding the prevailing sources in each site, aerosol biological impacts are higher for incomplete combustion sources resulting from two-wheel vehicles and domestic fires than from diesel vehicles (Dakar). Desert dust events seem to produce fewer biological impacts than anthropogenic sources.
  
  
  CONCLUSIONS
  Our study shows that combustion sources contribute to the high toxicity of F and UF PM of African urban aerosols, and underlines the importance of emission mitigation and the imperative need to evaluate and to regulate particulate pollution in Africa.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Val
authors.forename: Cathy
authors.initials: C
authors.lastname: Liousse
authors.forename: El Hadji Thierno
authors.initials: el HT
authors.lastname: Doumbia
authors.forename: Corinne
authors.initials: C
authors.lastname: Galy-Lacaux
authors.forename: Hélène
authors.initials: H
authors.lastname: Cachier
authors.forename: Nicolas
authors.initials: N
authors.lastname: Marchand
authors.forename: Anne
authors.initials: A
authors.lastname: Badel
authors.forename: Eric
authors.initials: E
authors.lastname: Gardrat
authors.forename: Alexandre
authors.initials: A
authors.lastname: Sylvestre
authors.forename: Armelle
authors.initials: A
authors.lastname: Baeza-Squiban
mesh_terms: D000336:Aerosols; D015415:Biomarkers / Q000378:metabolism; D001980:Bronchi / Q000187:drug effects* / Q000473:pathology; D002460:Cell Line; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D019570:Inhalation Exposure / Q000009:adverse effects; D008171:Lung Diseases / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008302:Mali; D018384:Oxidative Stress / Q000187:drug effects; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D018570:Risk Assessment; D012675:Senegal; D014504:Urban Health; D001335:Vehicle Emissions / Q000032:analysis / Q000633:toxicity*
chemical_list: D000336:Aerosols; D015415:Biomarkers; D016207:Cytokines; D018836:Inflammation Mediators; D052638:Particulate Matter; D012333:RNA, Messenger; D001335:Vehicle Emissions
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