Life-Time Dosimetric Assessment for Mice and Rats Exposed in Reverberation Chambers for the Two-Year NTP Cancer Bioassay Study on Cell Phone Radiation

Abstract

In this paper, we present the detailed life-time dosimetry analysis for rodents exposed in the reverberation exposure system designed for the two-year cancer bioassay study conducted by the National Toxicology Program of the National Institute of Environmental Health Sciences. The study required the well-controlled and characterized exposure of individually housed, unrestrained mice at 1900 MHz and rats at 900 MHz, frequencies chosen to give best uniformity exposure of organs and tissues. The wbSAR, the peak spatial SAR and the organ specific SAR as well as the uncertainty and variation due to the exposure environment, differences in the growth rates, and animal posture were assessed. Compared to the wbSAR, the average exposure of the high-water-content tissues (blood, heart, lung) were higher by ~4 dB, while the low-loss tissues (bone and fat) were less by ~9 dB. The maximum uncertainty over the exposure period for the SAR was estimated to be <49% (k=2) for the rodents whereas the relative uncertainty between the group was <14% (k=1). The instantaneous variation (averaged over 1 min) was <13% (k=1), which is small compared to other long term exposure research projects. These detailed dosimetric results empowers comparison with other studies and provides a reference for studies of long-term biological effects of exposure of rodents to RF energy.

A Radio Frequency Radiation Exposure System for Rodents Based on Reverberation Chambers

“…The analytical methodology is presented in detail in a companion paper [18]. The results are summarized here to indicate how the exposure system power output, needs to be adjusted to impart to the rodents approximately the same dose rate for different average body weights during aging and for different postures.…”

“…In addition to detailed analysis of the SAR uncertainty of rodents, the instantaneous variation due to rodent posture, size, and weight variation with a given exposure group has been performed as shown in Fig. 20 [18]. …”

“…The life-time averaged standard variation of the individual in the exposure group is 0.2 dB for the rat and 0.3 dB for the mouse. An extensive dosimetric research effort, detailed in a companion paper [18], documents the dose rate distribution in the body of rats and mice undergoing chronic RF exposure in the chambers presented in this paper. We conclude that the design and construction of the chambers satisfy the NTP RF test requirements for a large number of unconstrained rodents simultaneously exposed.…”

“…The required E-field strength was determined from numerical dosimetry performed with SEMCAD X (SPEAG, Switzerland) 1 with both the plane-wave integral representation of a reverberation chamber [17] and high-resolution animal models based on different size models covering the expected life span [18]. …”

Exposure Assessment in Millimeter‐Wave Reverberation Chamber Using Murine Phantoms

“…To overcome the limitations of anechoic chamber‐based exposure systems, the mode‐stirred reverberation chamber (RC) has been proposed for animal exposure ensuring isotropic exposure regardless of the animal posture and location inside the RC. Most RC‐related research applied to bioelectromagnetics has been conducted at frequencies up to 6 GHz [Jung et al, ; Wu et al, ; Aït‐Aïssa et al, ; Jin et al, ; Chakarothai et al, ; Shi et al, ; Shi et al, ; Gong et al, , ].…”