Source apportionment analysis of polyfluorinated alkyl substances in air-conditioned offices in Singapore

摘要

Volatile polyfluorinated alkyl substances (PFASs) including fluorotelomer alcohols (FTOHs) and fluorooctane sulfonamides/-ethanols (FOSAs/FOSEs), have become an increasing public health concern, since they are known to be degraded metabolically to the persistent and bioaccumulative ionic PFASs. The aim of this study is to investigate the indoor sources of volatile PFASs, which are apportioned into three broad categories - ventilation systems, occupant activities and indoor materials. The contribution of ventilation system is investigated through air sampling at the supply and return air ducts, while the influence of occupants' activities is studied via sampling during periods with and without occupants. The contribution of indoor materials is examined by sampling at four similar offices sharing one air-conditioning system. Analyte determination was based thermal desorption and GC-MS. Results indicated the concentrations of PFASs measured at the ducts of ventilation systems were at similar levels with those taken at center point of the office, implying the insignificant contribution from the HVAC system under the local context. In addition, no significant concentration differences were observed between air samples taken with and without human occupancy. This finding was further confirmed by the personal exposure measurement. This indicated the unlikely sources from the personal care products and other human activity related mechanisms for volatile PFASs in the office environment. The highest contributor of volatile PFASs was identified as the indoor materials. Significant variations in the chemical composition of the PFAS mixtures were also observed in offices with different types of products and furniture. The samples measured were also compared with those samples taken two years ago, and the result showed a considerable increase of 6:2 FTOH. All these findings suggest the commercial products used in local offices might be the major contributor to the indoor PFAS concentration and the sources are expected to dominate in the long term.