Traditional and novel halogenated flame retardants in urban ambient air: Gas-particle partitioning, size distribution and health implications.

Urban ambient air samples, including gas-phase (PUF), total suspended particulates (TSP), PM10, PM2.5 and PM1 airborne particle fractions were collected to evaluate gas-particle partitioning and size particle distribution of traditional and novel halogenated flame retardants. Simultaneously, passive air samplers (PAS) were deployed in the same location. Analytes included 33 polybrominated diphenyl ether (PBDE), 2,2',4,4',5,5'-hexabromobiphenyl (BB-153), hexabromobenzene (HBB), pentabromoethylbenzene (PBEB), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), decabromodiphenyl ethane (DBDPE), dechloranes (Dec 602, 603, 604, 605 or Dechorane plus (DP)) and chlordane plus (CP). Clausius-Clapeyron equation, gas-particle partition coefficient (Kp), fraction partitioned onto particles (φ) and human respiratory risk assessment were used to evaluate local or long-distance transport sources, gas-particle partitioning sorption mechanisms, and implications for health, respectively. PBDEs were the FR with the highest levels (13.9pgm-3, median TSP+PUF), followed by DP (1.56pgm-3), mirex (0.78pgm-3), PBEB (0.05pgm-3), and BB-153 (0.04pgm-3). PBDE congener pattern in particulate matter was dominated by BDE-209, while the contribution of more volatile congeners, BDE-28, -47, -99, and -100 was higher in gas-phase. Congener contribution increases with particle size and bromination degree, being BDE-47 mostly bounded to particles≤PM1, BDE-99 to > PM1 and BDE-209 to > PM2.5. No significant differences were found for PBDE and DP concentrations obtained with passive and active samplers, demonstrating the ability of the formers to collect particulate material. Deposition efficiencies and fluxes on inhaled PBDEs and DP in human respiratory tract were calculated. Contribution in respiratory track was dominated by head airway (2.16 and 0.26pgh-1, for PBDE and DP), followed by tracheobronchial (0.12 and 0.02pgh-1) and alveoli (0.01-0.002pgh-1) regions. Finally, hazard quotient values on inhalation were proposed (6.3×10-7 and 1.1×10-8 for PBDEs and DP), reflecting a low cancer risk through inhalation.

Gas/particle partitioning and particle size distribution of PCDD/Fs and PCBs in urban ambient air.

Urban ambient air samples, including gas-phase (PUF), total suspended particulates (TSP), PM10, PM2.5 and PM1 airborne particle fractions were collected to evaluate gas-particle partitioning and size particle distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs). Clausius-Clapeyron equation, regressions of logKp vs logPL and logKOA, and human respiratory risk assessment were used to evaluate local or long-distance transport sources, gas-particle partitioning sorption mechanisms, and implications for health. Total ambient air levels (gas phase+particulate phase) of TPCBs and TPCDD/Fs, were 437 and 0.07pgm-3 (median), respectively. Levels of PCDD/F in the gas phase (0.004-0.14pgm-3, range) were significantly (p<0.05) lower than those found in the particulate phase (0.02-0.34pgm-3). The concentrations of PCDD/Fs were higher in winter. In contrast, PCBs were mainly associated to the gas phase, and displayed maximum levels in warm seasons, probably due to an increase in evaporation rates, supported by significant and strong positive dependence on temperature observed for several congeners. No significant differences in PCDD/Fs and PCBs concentrations were detected between the different particle size fractions considered (TSP, PM10, PM2.5 and PM1), reflecting that these chemicals are mainly bounded to PM1. The toxic content of samples was also evaluated. Total toxicity (PUF+TSP) attributable to dl-PCBs (13.4fg-TEQ05 m-3, median) was higher than those reported for PCDD/Fs (6.26fg-TEQ05 m-3). The inhalation risk assessment concluded that the inhalation of PCDD/Fs and dl-PCBs pose a low cancer risk in the studied area.