Author's Reply to Letter to the Editor

Abstract

There appears to be a degree of confusion of what is measured in our paper. This has given the impression that a person situated near a large source of 50 Hz EM-® elds will receive a reduced dose from radon decay product and other aerosols in room air. In fact Figure 9c shows an increase in a -activity in the air itself near to the EM-® eld source. This observation therefore leads directly to increased dose to all body organs via inhalation without the need for any further mechanism. This was the principal purpose in reporting our ® ndings. Radon in indoor air In our experimental measurements TASTRAK a -sensitive plastic track detectors are used as a quantitative detector of a -radioactivity in air in which the energy of each recorded a -particle track is measured in each detector (Fews 1992a, b). Further analysis then allows the point of emission to be determined, discriminating between deposition on the detector surface itself (plateout) from that in the air in front of the detector. The use of these techniques has been particularly successful in studies of laser fusion plasmas at the Central Laser Facility, Rutherford Appleton Laboratory, where deconvolution methods have been employed to provide threedimensional reconstruction of thermonuclear temperature distribution in high intensity laser compressed deuterium± tritium fusion targets, i.e. a -activity in front of the detector is found by deconvolution (Fews et al. 1992, 1994). In the present application the use of these techniques is direct in that the residual energy and dip angle of a given recorded a -particle places limits on its point of emission in the air in front of the plastic. In practice many thousand a -particle tracks are recorded in each detector so that a full deconvolution analysis is also possible. Such analysis can yield the full height emission spectrum above the plastic surface. Thus the results in