To study whether chronic (over 17 months) exposure to vertical 50 Hz magnetic fields with regularly varying intensity affects noturnal 6-OHMS (6-hydroxymelatoninsulfate) production in female mice (n=140). The effects of 900 MHz radiofrequency irradiation were also studied.
The experiment was performed in the context of a long-term animal study on cancer-promoting effects of radiofrequency irradiation or 50 Hz magnetic field in mice after initiation with ionizing radiation. Therefore, groups were exposed at the beginning to ionizing radiation (4 Gy delivered as three sub-doses at 1 week intervals).
Artificial lighting was used with darkness from 7:00 p.m. to 7:00 a.m (15 to 180 lux).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 17 months
|
|
|
Exposure 2:
902.5 MHz
Modulation type:
CW
Exposure duration:
repeated daily exposure, 1.5 h/day, 5 days/week, for 17 months
|
|
|
Exposure 3:
902.4 MHz
Modulation type:
pulsed
Exposure duration:
repeated daily exposure, 1.5 h/day, 5 days/week, for 17 months
|
Female mice were randomly divided into six treatment groups (50 per group in 8 cages): cage control, sham RF, CW RF, pulsed RF, sham ELF, and ELF. All groups, except cage controls, were at the beginning exposed to 4 Gy ionising radiation delivered in three sub-doses at 1 week intervals.
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 17 months |
| Exposure source |
|
|---|---|
| Chamber | The animals were housed in groups of six or seven in plastic Macrolon III cages (with aspen chip bedding) that were rotated weekly. |
| Setup | The exposure system consisted of a wooden rack with 5 rectangular (0.4 x 1.2 m) coils producing a vertical homogeneous (±5%) magnetic field. The coils at the top and bottom had 15 turns, three middle coils had 10 turns. The vertical distances between the coils were 0.26 m. |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1.3 µT | unspecified | measured | - | - |
| magnetic flux density | 13 µT | unspecified | measured | - | - |
| magnetic flux density | 130 µT | unspecified | measured | - | - |
| Frequency | 902.5 MHz |
|---|---|
| Type | |
| Charakteristic |
|
| Exposure duration | repeated daily exposure, 1.5 h/day, 5 days/week, for 17 months |
| Modulation type | CW |
|---|
| Exposure source |
|
|---|---|
| Chamber | Three identical rectangular waveguides (24.8 x 20 cm, 125 cm long, and 190 cm with adapters) were used for CW, pulsed wave (E3) and sham exposures, respectively. |
| Setup | Up to 25 mice per waveguide were individually kept in small acrylic restrainers (32 mm diameter, adjustable length). Average weight phantoms filled with a sugar/salt/water solution [Hartsgrove et al., 1987] were put in the empty places. |
| Sham exposure | A sham exposure was conducted. |
| Additional info | The animal positions were randomised before each exposure because the location-dependent SAR variation was ±30%. |
| Frequency | 902.4 MHz |
|---|---|
| Type | |
| Charakteristic |
|
| Exposure duration | repeated daily exposure, 1.5 h/day, 5 days/week, for 17 months |
| Modulation type | pulsed |
|---|---|
| Duty cycle | 12.5 % |
| Repetition frequency | 217 Hz |
| Exposure source |
|
|---|
Neither the extremely low frequency magnetic field nor the radiofrequency irradiation affected excretion of 6-OHMS in nocturnal urine.
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