To study the influence of electromagnetic fields in the short-wave range (3-30 MHz) radio transmitter signals on salivary melatonin concentration in dairy cattle.
Two dairy herds at two farms were compared, one located at a distance of 500 m (exposed), the other at a distance of 4,000 m (unexposed) from the transmitter.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
3–30 MHz
Exposure duration:
continuous for 2 days, then 3 days transmitter off, continuous for another 5 days
|
|
| Frequency | 3–30 MHz |
|---|---|
| Type | |
| Exposure duration | continuous for 2 days, then 3 days transmitter off, continuous for another 5 days |
| Exposure source | |
|---|---|
| Distance between exposed object and exposure source | 500 m |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic field strength | 1.59 mA/m | - | - | - | - |
The mean values of the two initial nights did not show a statistically significant difference between exposed and unexposed animals. A chronic melatonin reduction effect seemed unlikely.
However, on the first night of re-exposure after the transmitter had been off for three days, the difference in salivary melatonin concentration between the two herds was statistically significant, indicating a two- to seven-fold increase of melatonin concentration.
Thus, a delayed acute effect of electromagnetic field on melatonin concentration cannot completely be excluded. However, findings should be interpreted with caution and further trials are required.
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