The association between exposure determined by radiofrequency personal exposimeters and human exposure: A simulation study

Abstract

The selection of an adequate exposure assessment approach is imperative for the quality of epidemiological studies. The use of personal exposimeters turned out to be a reasonable approach to determine exposure profiles, however, certain limitations regarding the absolute values delivered by the devices have to be considered. Apart from the limited dynamic range, it has to be taken into account that these devices give only an approximation of the exposure due to the influence of the body of the person carrying the exposimeter, the receiver characteristics of the exposimeter, as well as the dependence of the measured value on frequency band, channel, slot configuration, and communication traffic. In this study, the relationship between the field strength measured close to the human body at the location of the exposimeter and the exposure, that is, the field strength at the location of the human body without the human body present, is investigated by numerical means using the Visible Human model as an anatomical phantom. Two different scenarios were chosen: (1) For FM, GSM, and UMTS an urban outdoor scenario was examined that included a transmitting antenna mounted on the roof of one of four buildings at a street crossing, (2) For WLAN an indoor scenario was investigated. For GSM the average degree of underestimation by the exposimeter (relation of the average field levels at the location of the exposimeter to the field level averaged over the volume of the human body without the body present) was 0.76, and for UMTS 0.87; for FM no underestimation was found, the ratio was 1. In the case of WLAN the degree of underestimation was more pronounced, the ratio was 0.64. This study clearly suggests that a careful evaluation of correction factors for different scenarios is needed prior to the definition of the study protocol. It has to be noted that the reference scenario used in this study does not allow for final conclusions on general correction factors.

Assessment of personal exposure from radiofrequency-electromagnetic fields in Australia and Belgium using on-body calibrated exposimeters

“…We also demonstrated that the concurrent use of two on-body calibrated exposimeters provides exposure levels (for most of the measured frequency bands) nearly up to 2-3 times higher than those provided with a single non-on-body calibrated exposimeter. This is in line with earlier studies (Bolte et al, 2011;Neubauer et al 2010;Thielens et al 2015a) that demonstrated that a non-on-body calibrated exposimeter will underestimate personal exposure to incident RF EMFs due to the shielding of the body.…”

“…Neubauer et al (2008) suggested that frequency-specific calibration factor(s) should be applied while estimating RF-EMF exposures because RF-EMF exposures close to the human body are otherwise underestimated, which depends on the dimension of the human body, positions of the body-worn exposimeter(s) and frequency types. We have not reported the individual exposures measured by the ExpoM-RFs for summary statistics.…”

“…This could be because these studies did not correct for the consequence of body shielding on the measured personal exposure levels, which generally underestimates personal exposure levels (Bolte et al, 2011;Neubauer et al 2010;Thielens et al 2015a). Our study, however, took this issue into account by using frequency-specific on-body calibration factors while estimating personal exposure levels.…”

“…These studies used a single exposimeter worn by human subjects to measure whole body RF-EMF exposure, but the exposimeters were not calibrated on body. In fact the use of a single exposimeter, may result in measurement uncertainties, particularly those related to the body shielding effects, residual calibration, and the frequency response of the measurement device (Bolte et al, 2011;Gajšek et al, 2015;Iskra et al, 2011;Mann, 2010;Neubauer et al, 2010). Iskra et al (2011) suggested that the use of two exposimeters placed on different locations on the body may minimize the measurement uncertainties.…”

Measuring personal exposure from 900MHz mobile phone base stations in Australia and Belgium using a novel personal distributed exposimeter

“…However, exposure evaluations with exposimeters still have limitations (Bhatt et al, 2015), which give rise to measurement uncertainties. The uncertainties can reach up to 25-30 dB (Bolte et al, 2011;Iskra et al, 2011;Neubauer et al, 2010) and include shielding effects of the human body, the multidirectional nature of the incident RF-EMFs, residual calibration, the frequency response of the exposimeter, and the inability to detect signals below the lower detection limits, etc. (Bolte et al, 2011;Gajšek et al, 2015;Iskra et al, 2011 ;Mann, 2010;Neubauer et al, 2010).…”