Personal exposure to PM2.5 emitted from typical anthropogenic sources in Southern West Africa (SWA): Chemical characteristics and associated health risks
Authors: Xu Hongmei , Léon Jean-François , Liousse Cathy , Guinot Benjamin , Yoboué Véronique , Akpo Aristide Barthélémy , Adon Jacques , Ho Kin Fai , Ho Steven Sai Hang , Li Lijuan , Gardrat Eric , Shen Zhenxing , Cao Junji 
Published: October 2018

Abstract. Urbanisation is a strongly emerging issue in Southern West African (SWA) region. There is a general lack of understanding about the personal exposure to fine particulate matter (PM2.5), its chemical components and health risks related to the various anthropogenic sources in this region. In the current study, personal exposure to PM2.5 (PE PM2.5) sampling was for the first time carried out in dry season (January) and wet season (July) of 2016 to characterize PE PM2.5 from Domestic Fires (DF) for women and Waste Burning (WB) for students in Abidjan, Côte d'Ivoire and Motorcycle Traffic (MT) for drivers in Cotonou, Benin. The average PE PM2.5 mass concentrations were 331.7 ± 190.7, 356.9 ± 71.9 and 242.8 ± 67.6 μg m−3 at DF, WB and MT for women, students and drivers, which were 2.4, 10.3 and 6.4 times of the ambient PM2.5 concentrations, respectively. Mean concentrations of PE PM2.5 at DF (358.8 ± 100.5 μg m−3), WB (494.3 ± 15.8 μg m−3) and MT (335.1 ± 72.1 μg m−3) were much elevated in dry season, 15 % higher than that at DF and 55 % higher at both WB and MT. The changes in PE PM2.5 can be attributed to the source emissions, meteorological factors and personal activities. The results also show that geological material (35.8 %, 46.0 % and 42.4 %) and organic matter (34.1 %, 23.3 % and 24.9 %) were always the major components in PE PM2.5 at DF, WB and MT sites. It is worth noting that the contribution to PE PM2.5 from heavy metals was higher at WB (1.0 %) than at DF (0.7 %) and MT (0.4 %), which was influenced by the waste burning emission strongly, leading to the highest heavy metal non-cancer risks for students (5.1 and 4.8 times of women and drivers' non-cancer risks). In organic species of PE PM2.5, some fingerprints can be used to quantify the exposure concentrations and trace the source contributions from local typical anthropogenic sources to different samples. Women exposure concentration to polycyclic aromatic hydrocarbons (PAHs) in PM2.5 at DF (77.4 ± 47.9 ng m−3) was 1.6 times that for students at WB (49.9 ± 30.7 ng m−3) and 2.1 times for drivers at MT (37.0 ± 7.4 ng m−3), which is related to the solid fuels burning and grilling meat activities, resulting in 5 times higher of cancer risk safety threshold (1 × 10−6) to women. Phthalate esters (PAEs), commonly used as plasticizers in many products, were observed to be extremely high in student exposure PM2.5 samples (1380.4 ± 335.2 ng m−3) at WB site, owing to the waste burning emission obviously. Drivers exposure to fossil fuel emission (especially traffic) markers-hopanes in PE PM2.5 at MT (50.9 ± 7.9 ng m−3) was 2.0–2.3 times higher than women at DF (17.1 ± 6.4 g m−3) and students at WB (15.6 ± 6.1 ng m−3), correlating with the elevated exposure to traffic emissions for drivers. Overall, the study shows that wood combustion, waste burning, fugitive dust and motor vehicle emissions dominated PE PM2.5 mass and contributed to its toxicities mainly. Heavy metals and organic chemicals in PE PM2.5 in SWA brought about Pb and Mn non-cancer health risks for students at WB site and serious PAHs cancer risks for women at DF site via inhalation pathway. This study provides basic data and initial perspective of PM2.5 personal exposure and health risk assessment in underdeveloped area to encourage the government to improve the air quality and living standard of residents in this region.