"RF multi-exposure system

A reverberation chamber was designed as a whole body exposure system for in vivo experiments, which allowed simultaneous exposure to multiplemobile phone frequencies . The multiple-frequency whole body exposure system generates a real CDMA signal and a WCDMA signalsimultaneously. Generic signals which are modulated exactly the same as the reference signals used for SAR compliance tests both for CDMA and WCDMA phones, were used for the exposure system. To generate signals, a microprocessor unit (MPU) chip with prewritten CDMA and WCDMA format codes was used. The MPU, in turn, controlled a central processing unit (CPU) to generate real CDMA and WCDMA test signals. For the cellular system, a real CDMA signal, at 848.5 MHz, was generated and subsequently amplified using a high power amplifier module(DCS60WHPA_CW; Kortcom Co., Anyang, Gyeonggi-do, Korea) after passing through a digital attenuator (Supplementary material, available on line). The maximum available input power was 60 W. For the WCDMA system, a real WCDMA signal at 1950 MHz was generated and subsequently amplified using another high power amplifier module(PCS60WHPA_CW; Kortcom Co., Anyang, Gyeonggi-do, Korea) after passing through a sepa rate digital attenuator. The maximum available input power was 60 W. The digital attenuator was an 11- bit digital PIN diode attenuator (Model 349; General Microwave Co., Farmingdale, NY, USA) and the attenuator controlled the output power level. The transmitting antennas used for the CDMA and the WCDMA frequency are the commercial products (patch type; KCAN0800PA for CDMA, KC ANl 900PA for WCDMA,Korea telecommunica tion company Ltd, Buchon, Kyunggi-do, South Korea). A computer controlled the exposure level and theexposure time-schedule . The external dimensions of the reverberation chamber were 2295 x 2293 x 1470 mm. These dimensions satisfy the requirements for the minimum number of modes required at the lowest useable frequency (LUF) of interest. Additionally,the stainless wall of the chamber functioned as an electromagnetic shield. Five cages were placed on the table (test area), which is located inside of the exposed chamber and the field uniformity in the test area was confirmed by measuring the field strength for 1 min at 24 points. The field uniformity in the cage was also confirmed by measuring the field strength for 1 min at 27 points on the surface of the cage at a typical exposure location (Figure 1). The electric field distribution was measured inside the chamber using a 3-axisisotropic probe (HI-6005; ETS-Lindgren, Cedar Park, TX, USA). The field distribution was well within 3 dB in the region of interest. Assuming the field vectors were uniform in all directions, the SAR distribution of a caged rat was calculated using a finite differencetime domain (FDTD) tool (XFDTD version 6.5; Remcom Inc., State College, PA, USA) in six orthogonal directions. Two independent polarisations were used for each direc tion. The rat model (Chugnam National University, Daejon, Korea) used for simulation had 40 tissues and a 1-mm voxel size. The calculated SAR values were then averaged and multiplied by the measured

r.m.s. electric field to estimate the real SAR values for a given input power. For 2.0 W/kg of SAR, the power output was controlled at 30 W for CDMA and at 18 W for WCD MA.

Experimental design

The experimental animals were assigned to the following four groups (n = 20/group): (1) Male sham RF exposure, (2) male combined RF exposure, (3) female sham RF exposure, and (4) female combined RF exposure. RF exposure was performed by whole body exposure in the exposure chamber 45 min/day, 5 days/week, for 12 months. Combined RF exposed

rats (groups 2 and 4) were simultaneously exposed to CDMA (2.0 W/kg) and WCDMA (2.0 W/kg) signals. Daily RF or sham exposure was performed in the morning or in the afternoon altern atively. The position of the cages and tum of exposure were changed every day (Figure 2). Sham-exposed rats (groups 1 and 3) were placed in the exposure chamber without exposure to magnetic field signals. To prevent treatment bias, all the exposure and data analysis were performed using blinded methods.

Clinical examination

To determine mortality or morbidity, RF-exposed and sham-exposed rats were observed daily. After 12 months of exposure, ratswere sacrificed and autopsied . Urine samples for urinalysis from indivi dual rats were collected for 24 h before the autopsyusing metabolic cages and urinalysis was performed by the NeoDin Medical Institute (Seoul, Korea). Blood was sampled from the posterior vena cava for haematological analysis using a Hemavet 950 Multi species Hematology Analyzer (DREW ScientificInc., Oxford, CT, USA) and serum samples were measured using an automated clinical chemistry analyzer (Fuji Dri-Chem 4000i; Fujifilm Co ., Tokyo, Japan). During autopsy, all major organs (brain, heart, lung, kidney, intestine, liver, reproductive organs, thymus) were evaluated grossly and fixed in 10% buffered formalin or Bouin's fixative for histopathological analysis. Any abnormalities in other organs were noted and the organs were collected for histopathological evaluation. Fixed Statistical analysis

The SPSS software (Version 15.0; SPSS Inc, Chicago, Illinois, USA) was used for evaluation of the data . A calculation was made of the meanand standard deviation of each evaluated parameter. To compare the value by RF exposure, we used the Mann-Whitney U-test. Results were deemed statis tically significant at p < 0.05."

Sprague-Dawley rats, male

HAWC