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, PM_2.5 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 (K_p), 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 > PM_2.5. 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.