Epidemiological study (observational study)

Heart rate variability (HRV) analysis in radio and TV broadcasting stations workers epidem.

By: Bortkiewicz A, Gadzicka E, Szymczak W, Zmyslony M

Published in: Int J Occup Med Environ Health 2012; 25 (4): 446-455

Aim of study (acc. to author)

A case-control study was conducted in Poland to investigate the heart rate variability in workers exposed to UHF (300-3000 MHz) - VHF (30-300 MHz) radio frequency electromagnetic fields.

Further details

The workers were categorized into two exposure groups according to the individual exposure level: low-level exposure group (mean lifetime dose of electric field strength: 288 V²h/m² (UHF), 6570 V²h/m² (VHF), 6848 V²h/m² (UHF+VHF); mean value: 0.1 V/m (UHF), 0.3 V/m (VHF), 0.3 V/m (UHF+VHF); maximal value: 5.3 V/m (UHF), 0.9 V/m (VHF), 7.9 V/m (UHF+VHF)) and high-level exposure group (mean lifetime dose of electric field strength: 130 130 V²h/m² (UHF), 640 583 V²h/m² (VHF), 771 200 V²h/m² (UHF+VHF); mean value: 1.1 V/m (UHF), 2.5 V/m (VHF), 2.7 V/m (UHF+VHF); maximal value: 6.8 V/m (UHF), 15.2 V/m (VHF), 16.7 V/m (UHF+VHF)).

Endpoint/type of risk estimation

heart rate variability

Type of risk estimation:

prevalence

(relative risk (RR))

Exposure

- 66–727 MHz
- UHF fields
- Radio/TV transmitter
- TV broadcast (VHF/UHF)
- occupational

Assessment

interview: job history, job duration
measurement: spectral analysis for a typical broadcasting station in the UHF and VHF frequency bands
calculation: to assess individual exposure, following parameters were calculated separately for VHF, UHF and VHF+UHF: maximum value of electric field strength, mean value, lifetime dose based on years of employment and job timetable

Exposure groups

Group	Description
Reference group 1	unexposed workers
Group 2	low-level exposed workers
Group 3	high-level exposed workers

Population

Group:
- men
Age: 28–66 years
Observation period: not stated
Study location: Poland

Case group

Characteristics: workers at 4 broadcast stations

Control group

workers at 4 radio link stations (elements of a telecommunication system in which signals are transmitted using EM waves focused into very narrow beams by directional (mostly parabolic) antennas mounted in highly inaccessible locations)

Study size

	Cases	Controls
Eligible	71	42

Statistical analysis method:

logistic regression
ANOVA

(adjustment:

age
smoking, alcohol consumptions

)

Results (acc. to author)

36 (51%) out of 71 of the exposed workers reported cardiovascular symptoms, including dyspnoea, pain or discomfort in the chest or feeling of irregular heartbeat. In the control group, similar complaints were reported by 15 (29%) workers. The heart rate was higher among the exposed workers than among the unexposed workers. Standard deviation of RR intervals was found to be significantly lower in the low level-exposed group (mean +/- standard deviation 42.5 +/- 24.7 ms) compared to the control group (62.9 +/- 53.5 ms). The risk of lowered standard deviation of RR intervals was significantly increased (OR 2.37; p=0.023) in high level exposed group. Both exposed groups presented significantly higher very low and low frequency power spectrum values than the control group. The exposed groups were characterized by the dominance of the sympathetic system (low frequency/high frequency ratio 1.3 +/- 0.35).
The authors concluded that exposure to radiofrequency electromagnetic fields may affect the neurovegetative regulation of the cardiovascular system.

Study funded by

European Union (EU)/European Commission

Chen Q et al. (2013): ECG changes in factory workers exposed to 27.2 MHz radiofrequency radiation
Andrzejak R et al. (2008): The influence of the call with a mobile phone on heart rate variability parameters in healthy volunteers
Wilen J et al. (2007): Changes in heart rate variability among RF plastic sealer operators
Israel M et al. (2007): Cardiovascular risk under electromagnetic exposure
Vangelova K et al. (2006): Cardiovascular risk in operators under radiofrequency electromagnetic radiation
Braune S et al. (1998): Resting blood pressure increase during exposure to a radio-frequency electromagnetic field
Bortkiewicz A et al. (1996): Heart rate variability in workers exposed to medium-frequency electromagnetic fields