To confirm previous data on the effects of 2450 MHz microwave exposure on immunological processes and teratology in rats.
A series of Soviet publications published from 1974-1986 (Vinogradov et al. 1974, Vinogradov et al. 1975, Shandala et al. 1983, Vinogradov et al. 1985, Vinogradov and Naumenko 1986, Shandala and Vinogradov 1982) dealt with the effects on the immune system of rats exposed to radiofrequency fields at 2375 MHz (0.1-10 W/m²). Because the findings of these studies served in part as the basis for setting exposure limit values in the former USSR, it was deemed necessary to perform confirmation studies using modern dosimetric and biological methods.
In the previous studies it was reported that radiofrequency exposure disrupted the antigenic structure of rat brain tissue and induced differences in immune responses. Moreover, these studies showed that blood serum from irradiated rats injected into intact non-exposed female rats on the 10th day of pregnancy led to increased postimplantation embryo mortality and decreased fetus body weight and size.
For immunological investigation blood, brain and liver of 48 rats (16 rats/group; sham exposure, exposure, cage control) was taken on days 7 (5 rats per group) and 14 (11 rats per group) after exposure.
For teratological experiments, blood sera of the 11 rats (14 days following exposure) were prepared. Sera from exposed and sham exposed rats were administered to two groups of female rats on the 10th day of pregnancy (21 rats/group). A third group of pregnant females received no treatment (control group).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
2,450 MHz
Exposure duration:
continuous for 7 hr/day, 5 days/week for 30 days
|
|
| Frequency | 2,450 MHz |
|---|---|
| Type | |
| Charakteristic | |
| Polarization |
|
| Exposure duration | continuous for 7 hr/day, 5 days/week for 30 days |
| Additional info | +/- 50 MHz |
| Exposure source |
|
|---|---|
| Distance between exposed object and exposure source | 2.35 m |
| Chamber | 6 m x 3 m x 3.5 m anechoic chamber with walls, floor and ceiling covered with 0.05 m high ferrite-based pyramidal RF-absorber elements; outer walls of the chamber covered with welded steel sheets; antenna mounted on a bracket made of plastic and wood above the chamber's floor |
| Setup | 16 cages made of Plexiglas and PVC arranged in a ring inside the chamber with one rat per cage; ring of cages placed on 0.18 m high styrofoam stands |
| Sham exposure | A sham exposure was conducted. |
| Additional info | chamber 1 for the sham-exposed animals was 10 m x 3 m x 3.5 m, and chamber 2 for RF-exposed animals was 6 m x 3 m x 3.5 m; to make the chambers visually the same size, a black opaque curtain was put in chamber 1 |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| SAR | 0.16 W/kg | - | estimated | whole body | at 5 W/m² |
| SAR | 0.16 W/kg | average over mass | estimated | brain | - |
| SAR | 9.9 W/kg | peak value | calculated | partial body | tail skin |
| SAR | 1 W/kg | peak value | calculated | brain | - |
| power density | 4.95 W/m² | average over time | measured | - | 3.12 W/m² - 7.82 W/m² at the geometric center of the cages measured 0.22 m above the floor in the absence of animals and cages |
| power | 71 W | - | measured | - | +/- 7.3 W antenna input power |
| power density | 5 W/m² | - | measured | - | incident power in the cage |
The data of the immunological examination partly confirmed the results of the Soviet research groups on the possible induction of autoimmune responses (increase of antibodies against brain antigens in the exposed group on the 14th day after exposure) and suggested stress reactions from radiofrequency exposure on day 7 after exposure (indicated by an increase in the content of amino acids bound with nitric oxide compounds, as well as lipids, including non-saturated fatty acids with short chains and their oxidation products).
The findings on prenatal development of offspring suggested possible adverse effects of the blood serum from exposed rats on pregnancy and embryo-foetal development in rats, in agreement with the earlier results of Shandala and Vinogradov (1982). The present study showed higher total in utero mortality (pooled data of days 15 and 20 of pregnancy) in rats injected with blood serum from exposed animals (55.6≥4.0%) than in rats injected with serum from sham exposed animals (11.7≥3.3%).
The application of these results in developing exposure standards is limited.
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