Study type: Medical/biological study (observational study)

Variations of melatonin and stress hormones under extended shifts and radiofrequency electromagnetic radiation med./bio.

By: Vangelova KK, Israel MS
Published in: Rev Environ Health 2005; 20 (2): 151-161
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Aim of study (acc. to author)

To study the time-of-day variations in urinary levels of 6-sulphatoxy melatonin and three stress hormones in operators working fast-rotating extended shifts (16 to 18 h with a 24 h-stay in the station (9:00 to 9:00) followed by 3 days off) under radiofrequency electromagnetic radiation.

Background/further details

The excretion rate of the hormones was monitored at 4-hour intervals in a group of 36 male operators comprising 12 broadcasting station operators (high level of exposure), 12 TV station operators (low-level of exposure), and a control group of 12 satellite station operators (very low level of exposure).
This study is a part of complex investigation of the health risk assessment of occupational radiofrequency electromagnetic irradiation exposure (National Center of Hygiene, Medical Ecology and Nutrition, Report No 2.1/0.1: Assessment of the effect of low-level radiofrequency EMR on secretion of melatonin, the level of stress hormones and cardiovascular system. National Center of Hygiene, Medical Ecology and Nutrition, Sofia, Bulgaria, 2003; 1-128.).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 6–25 MHz
Exposure duration: repeated exposure for 1 day on and 3 days off
Exposure 2: 66.5–900 MHz
Exposure duration: repeated exposure for 1 day on and 3 days off
Exposure 3: 5.85–6.245 GHz
Exposure duration: repeated exposure for 1 day on and 3 days off

Exposure 1

Main characteristics
Frequency 6–25 MHz
Type
Exposure duration repeated exposure for 1 day on and 3 days off
Exposure setup
Exposure source
Setup Three groups of 12 operators each were investigated working fast-rotating extended shifts in three telecommunication stations, i.e., a broadcasting (BC) station, a TV station and a satellite (SAT) station, respectively. The operators from the three groups worked a 4-day cycle schedule: one extended shift (16 to 18 h) with a 24-h stay in the station, followed by 3 days off.
Additional info From the measurements and calculations, it was concluded that the level of exposure of BC station operators was high, whereas that of TV and SAT station operators was low, the lowest in SAT operators. The latter group was used as a control because no other suitable group could be found in terms of shift system and job characteristics.
Parameters
Measurand Value Type Method Mass Remarks
power density 3.1 µW/cm² average over time measured and calculated - TWAmean
power density 137 µW/cm² average over time measured and calculated - TWAmax
Measurement and calculation details

Electromagnetic radiation exposure was assessed by measuring the intensities and flux densities of the electromagnetic field on the typical work places of the staff according to the duty records for the near zone with NFM-1 (Germany) and for the far zone with RAHAM (USA). The intensities and the flux densities of the EMF were within the limits of the ICNIRP, except for the antenna field of the broadcasting station, where the eventual stay of the operators is very limited. To compare the electromagnetic exposure in the stations, the intensities in the short wave range were transformed into flux densities for a flat electromagnetic field. Using the "script of scenario" method, the time-weighted average (TWA) was calculated, which included the mean and maximum TWA.

Exposure 2

Main characteristics
Frequency 66.5–900 MHz
Type
Exposure duration repeated exposure for 1 day on and 3 days off
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
power density 1.89 µW/cm² average over time measured - TWAmean
power density 5.24 µW/cm² average over time measured - TWAmax

Exposure 3

Main characteristics
Frequency 5.85–6.245 GHz
Type
Exposure duration repeated exposure for 1 day on and 3 days off
Exposure setup
Exposure source
  • satellite (SAT) station
Parameters
Measurand Value Type Method Mass Remarks
power density 1.6 µW/cm² average over time measured - TWAmean
power density 3.57 µW/cm² average over time measured - TWAmax

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Radiofrequency electromagnetic irradiation had no effect on the typical diurnal pattern of 6-sulphatoxy melatonin. High-level radiofrequency electromagnetic irradiation exposure significantly increased the excretion rates of cortisol, adrenaline, and noradrenaline, whereas changes under low-level exposure did not reach significance.
In conclusion, the excretion of 6-sulphatoxy melatonin retained a typical diurnal pattern under extended shifts and radiofrequency electromagnetic irradiation, but showed an exposure-effect relation with stress hormones.

Study character:

Study funded by

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