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A study of 50 homes and their appliances examined whether a detailed appliance-use questionnaire and survey would yield data comparable with direct personal monitoring. This was coupled with direct measurement of the appliances in use to determine the field at 50 cm and 1 m. The findings were that individual time-weighted average (TWA) exposures calculated from questionnaire and activity diaries in conjunction with the appliance magnetic field were unrelated to actual personal exposure measurement. It was concluded that questionnaires are of little or no value for TWA estimation. However, peak exposure and short-term temporal variability could be modelled in subjects spending at least 15 min per day within 1 m of an operating microwave cooker or conventional cooker. This method could be extended to other appliances.
Preece et al. (Tue,) studied this question.