Looking at specific classes of PFAS, the nonpolar PFAS are all >99.9% in the air phase, reflecting their extremely high volatility. Non-PFAS contaminants with similar phase distribution properties may be limited to alkanes and refrigerant compounds (e.g., R-12). Weakly polar PFAS (e.g., FTIs, FTACs) are primarily found in air, but with an appreciable organic phase contribution (0.1-20%). The more polar FTOHs are more abundant in the organic phase (2-70%). These distribution patterns of fluorotelomer compounds are comparable to those of medium to long alkyl compounds with no or a weakly polar functional group (e.g., n-hexadecane, dihexyl ether) and, notably, cyclic volatile methylsiloxanes (e.g., D5). PFASAs and their derivatives are even more in the organic phase, similar to moderately hydrophobic persistent organic pollutants (POPs), e.g., hexachlorocyclohexanes, hexachlorobenzene, and polychlorinated biphenyls with low degree of chlorination. Only short-chain PFAS with a polar functional group may be present in water at >1%. Note that PFASAs and FASAs are weak acids and may ionize in water and partition more into water, which is not accounted for in the plot. Figure shows a plot for 134 neutral PFAS using the log Kaw and log Kow values predicted by COSMOtherm. These neutral PFAS are from the lists of Kissel et al. and our previous study. The data points are even more widely distributed, although the plot again shows that air is the most important phase and that the air/organic phase distribution can be an important fate determinant, except for short-chain polar PFAS, which can also be in water.