The polarities of a wide range of ionic liquids have been determined using the Kamlet-Taft empirical polarity scales α, β and π*, with the dye set Reichardt's Dye, N,N-diethyl-4-nitroaniline and 4-nitroaniline. These have been compared to measurements of these parameters with different dye sets and to different polarity scales. The results emphasise the importance of recognising the role that the nature of the solute plays in determining these scales. It is particularly noted that polarity scales based upon charged solutes can give very different values for the polarity of ionic liquids compared to those based upon neutral probes. Finally, the effects of commonplace impurities in ionic liquids are reported.

These results can be analysed in terms of the charge density present. This analysis suggests that typically 2000 excess negative charges per cm3 are required to match the measured DC fields. Such space charge will result in unipolar aerosol charging in excess of the normal bipolar steady state charge distribution of pollutant aerosols. This may lead to increased lung deposition on inhalation.

The observations demonstrate a mode of increased exposure to pollutant aerosols under high voltage power lines by increased deposition on the body. The total (indoor + outdoor) 218Po and 214Po dose to the basal layer of facial skin is estimated to be increased by between 1.2 and 2.0 for 10% of time spent outdoors under high voltage power lines.

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