Effects of wind and electric fields on 218Po deposition from the atmosphere

To estimate, under atmospheric conditions, 218Po deposition on a sphere representing the human head and compare with the effects of the maximum electric field to be found under a transmission line.

The effect of the wind in the absence of electric fields was calculated using the Reynolds Analogy between heat and mass transfer. The effect of the electric field was shown to be large compared with that of turbulence. A 'capture radius' due to the field was then estimated and charged 218Po particles blown into this region were assumed to be captured.

The deposition ratio was proportional to gammaV0.4E0(0.67), where gamma = charged fraction of 218Po, V = velocity and E0 = surface electric field. With the charged fraction ranging from 0.9% to 3.2%, a surface field on 280 kV m(-1) and a wind speed of 3 m s(-1), the deposition ratio ranged from 3.4 to 9.3. The surface field is several orders of magnitude higher than the average personal exposures that have been measured in epidemiological studies and the effect does not appear to be of epidemiological significance. At low velocities, the predictions of this model are in agreement with the measurements of Henshaw et al.

218Po deposition by environmental AC fields cannot be advanced as an explanation for the reported associations between childhood leukaemia and electrical installations.