Recurring biomass burning-induced smoke haze is a serious regional air pollution problem in Southeast Asia (SEA). The June 2013 haze episode was one of the worst air pollution events in SEA. Size segregated particulate samples (2.5-1.0 μm; 1.0-0.5 μm; 0.5- 0.2 μm; and <0.2 μm) were collected during the June 2013 haze episode. PM2.5 concentrations were elevated (up to 329 μg/m(3)) during the haze episode, compared to those during the nonhaze period (11-21 μg/m(3)). Chemical fractionation of particulate-bound trace elements (B, Ca, K, Fe, Al, Ni, Zn, Mg, Se, Cu, Cr, As, Mn, Pb, Co, and Cd) was done using sequential extraction procedures. There was a 10-fold increase in the concentration of K, an inorganic tracer of biomass burning. A major fraction (>60%) of the elements was present in oxidizable and residual fractions while the bioavailable (exchangeable) fraction accounted for up to 20% for most of the elements except K and Mn. Deposition of inhaled potentially toxic trace elements in various regions of the human respiratory system was estimated using a Multiple-Path Particle Dosimetry model. The particle depositions in the respiratory system tend to be more severe during hazy days than those during nonhazy days. A prolonged exposure to finer particles can thus cause adverse health outcomes during hazy days. Health risk estimates revealed that the excessive lifetime carcinogenic risk to individuals exposed to biomass burning-impacted aerosols (18 ± 1 × 10(-6)) increased significantly (P < 0.05) compared to those who exposed to urban air (12 ± 2 × 10(-6)).