Characterization of metal(loid)s in indoor and outdoor PM2.5 of an office in winter period

The characterization of indoor (a naturally ventilated office) and outdoor (adjacent courtyard) metals in PM_2.5 during a winter period in Xi'an, China were carried out. The results indicated that the average mass concentrations of PM_2.5 in indoor and outdoor environments all exceeded the daily average limit of 75 µg m^–3 set by the Chinese government. The dominant metals in PM_2.5 were Ca, Al, Zn, Mg, Fe, and Pb in both indoor and outdoor air. Concentration of As was much higher than the standard of 6 ng m^–3 issued by the government. Enrichment factor analysis showed that anthropogenic emissions might be the primary sources of As, Cd, Pb, and Zn, while crust was the main origin of Co. A majority of indoor-to-outdoor concentration ratios of metal were lower than 1 indicating mostly the contribution of outdoor sources rather than indoor ones. As and Cr in both indoor and outdoor air posed the highest noncarcinogenic and carcinogenic risks, respectively. The noncarcinogenic and carcinogenic risks were 2.74 and 2.54 × 10^?4 indoor and 4.04 and 3.87 × 10^?4 outdoor, which suggested that possible adverse health effects should be of concern.