A daily black carbon (BC) exposure assessment of forty 10-12 years-old children was conducted in the Seoul Metropolitan Area from August 2015 to January 2016. Each participant carried a microaethalometer to measure BC concentrations for 24 h while their whereabouts and microenvironments (MEs) were recorded via a time-activity diary (TAD) and follow-up interviews. Analysis of variance (ANOVA) was employed to compare average BC levels by potential risk factors including demographic, temporal, residential, and indoor/outdoor/transportation activity variables. The children's average daily exposure was 1.93 g/m(3), with a range of 0.2-85.43 g/m(3) (mean daily individual exposure ranges from 0.54 to 4.80 g/m(3)). Even children attending the same elementary school reported BC exposures which differed by approximately 40%, primarily because of individually distinct time-activity patterns and the MEs with which each child interacted. On weekends (Saturdays and Sundays) (1.86 2.50 g/m(3)) and holidays (Saturdays, Sundays, and vacation) (1.71 2.48 g/m(3)), children were subject to reduced exposures to BC, likely due to decreased surrounding traffic volumes and different time-activity patterns on weekend days compared to on weekdays (from Mondays to Fridays) (1.95 2.44 g/m(3)) or school days (weekdays during the school semesters) (2.05 2.43 mu g/m(3)). Commuting in diesel vehicles (often to private academies) or in the subway, cooking, and environmental tobacco smoke were all found to elevate BC exposure. Likewise, proximity to traffic sources and parental indoor smoking contributed to the enhancement of residential BC concentrations. Our findings suggested a need to emplace proactive measures including diesel fleet regulation and smoking cessation campaigns to protect children from high levels of BC exposure. (C) 2017 Elsevier Ltd. All rights reserved.