Perfluoroalkyl substances in UK indoor and outdoor air: spatial and seasonal variation, and implications for human exposure.

This study reports atmospheric concentrations of a number of perfluoroalkyl substances (PFASs) in homes, offices, and outdoor locations in Birmingham, UK during 2008 and 2009. Concentrations indoors exceed significantly those outdoors, suggesting indoor emissions are driving outdoor contamination. The exception is N-ethyl perfluorooctane sulfonamide (EtFOSA), for which indoor and outdoor concentrations are statistically indistinguishable, implying other sources for this compound. Concentrations of all PFASs at 10 urban outdoor locations showed little spatial variability (RSD=53-85%). At 2 urban locations and 1 semi-rural location in England, monthly variations in outdoor concentrations were measured over 1 year and shown to be in line (RSD=39-110%) with the low spatial variability in Birmingham. This low spatial and temporal variability implies sources at locations monitored are diffuse in nature. Concentrations of N-ethyl perfluorooctanesulfonamidoethanol (EtFOSE) in outdoor air were significantly higher at one of the Birmingham urban sites than at the semi-rural location. Indoor concentrations of perfluorohexanesulfonate (PFHxS) exceeded those of perfluorooctanesulfonate (PFOS). Combined with the fact that PFHxS concentrations in outdoor air in this study exceed substantially those measured in the UK in 2005; this is consistent with the hypothesis that PFHxS use is increasing in response to restrictions on the use of PFOS. Concentrations of PFOS in offices exceed significantly those in homes. Month-to-month variations in concentrations in 4 living rooms and 1 office were measured over a year. Relative standard deviations (RSD) for individual PFASs in these locations were 47-160%, providing information about the uncertainty associated with exposure assessments based on single measurements. The observed variability could not be attributed to changes in room contents, nor to seasonality. Human exposure via inhalation appears a minor pathway.