An unwanted hitchhiker: assessment of per- and polyfluoroalkyl substances (PFAS) in vehicle cabin air conditioner and engine filters

Per- and polyfluoroalkyl substances (PFAS) are highly mobile and widespread chemicals that are associated with an expanding list of adverse health effects. Given their ubiquity and high mobility, dust has become a suitable matrix for assessing potential indoor levels of PFAS. Currently, vehicles represent a largely underexplored source of PFAS contamination in dust. We propose that vehicle cabin air conditioning (AC) filters can be used as opportunistic sampling devices for exploring PFAS levels in dust inherently present within vehicles. This study monitored 47 PFAS in cabin AC filters (<i>n</i> = 10) and engine air filters (as a comparison, <i>n</i> = 10) <i>via</i> high performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS). Cabin AC filters, which filter air circulated within the passenger compartment, contained higher PFAS concentrations (median ∑PFAS = 92 ng g^-1) than the engine air filters, which filtered outdoor air feeding into the vehicle engine (median ∑PFAS = 2 ng g^-1). In cabin AC filters, the dominant PFAS were polyfluoroalkyl phosphate esters (PAPs), which accounted for 45% of ∑PFAS by concentration. In engine filters, the dominant PFAS were fluorotelomer sulfonic acids (dominated by one engine filter) and perfluoroalkyl carboxylic acids, which represented 59% and 20% of the ∑PFAS, respectively. This study demonstrated that we are likely exposed to PFAS inside vehicle cabins and that cabin AC filters are a well-suited sampling matrix worth further exploration.