Levels, profiles and gas-particle distribution of atmospheric PCDD/Fs in vehicle parking lots of a South China metropolitan area

Vehicle exhaust is one important PCDD/F source in urban areas. In this study, occurrence and inhalation of atmospheric PCDD/Fs in three enclosed/semi-enclosed large-scale vehicle parks were investigated. The park for heavy-duty diesel-trucks exhibited the highest atmospheric 2,3,7,8-PCDD/F concentrations (17.7 +/- 4.3 pg m(-3), 0.818 +/- 0.264 pg I-TEQ m(-3)), followed sequentially by those for liquefied petroleum gas-buses and for unleaded gasoline-cars. High-chlorinated congeners/homologues dominated 2,3,7,8-PCDD/F profiles. Principal component analysis indicated their similarities with tailpipe studies. More than 70% of PCDD/Fs were particle-bound and their congener/homologue patterns differed from those of gaseous PCDD/Fs. In all studied parks logarithms of the gas/particle partitioning coefficients (K(p)s) of PCDD/F homologues were linearly correlated with those of their sub-cooled vapor pressures (p(L)s). Daily PCDD/F doses inhaled by park-workers were estimated to be between 0.099-0.227 pg I-TEQ kg(-1) d(-1). Their probabilistic incremental lifetime cancer risks were 1.08 x 10(-5)-2.07 x 10(-5), which were in the acceptable range (1.0 x 10(-4)-1.0 x 10(-6)). However, all data from the diesel-truck park significantly exceeded the upper limit for PCDD/Fs in ambient air of Japan (0.6 pg TEQ m(-3)). Hence, air pollution and adequate ventilation should be considered during the design and construction of such enclosed/semi-enclosed parks. (C) 2013 Elsevier Ltd. All rights reserved.