Epidemiological study (observational study)

ECG changes in factory workers exposed to 27.2 MHz radiofrequency radiation epidem.

By: Chen Q, Xu G, Lang L, Yang A, Li S, Yang L, Li C, Huang H, Li T

Published in: Bioelectromagnetics 2013; 34 (4): 285-290

Aim of study (acc. to author)

A case-control study was conducted in China to investigate the effect of 27.2 MHz radiofrequency electromagnetic fields on electrocardiograms of female workers operating radiofrequency machines at a shoe factory.

Further details

In the shoe factory, there were 80 radiofrequency welding machines operating at 8 kV in 30 out of 80 machines and 4 kV for the remaining machines. Measurements of the electric field strength were performed at 27 welding machines in the factory.

Endpoint/type of risk estimation

electrocardiogram changes

Type of risk estimation:

prevalence

(odds ratio (OR))

Exposure

- 27.2 MHz
- RF
- occupational

Assessment

questionnaire: work shift, occupational history
measurement: 6 min measurement of the electric field strength of 27 out of the welding machines in the factory
calculation: 6 min root mean square value of electric field strength

Exposure groups

Group	Description
Reference group 1	control group: unexposed
Group 2	exposed workers: 3 months - 2 years
Group 3	exposed workers: > 2 years

Population

Group:
- women
Age: 18–48 years
Observation period: not stated
Study location: China

Case group

Data source: Guangdong Prevention and Cure Centre of Occupational Diseases, Guangzhou
Exclusion criteria: hyperthyroidism

Control group

Selection:
- female workes of the same factory without exposure to radiofrequency or toxic compounds

Study size

	Cases	Controls
Eligible	225	100
Participants	224	98

Statistical analysis method:

logistic regression
ANOVA

(adjustment:

age
smoking, alcohol consumption, exposure duration

)

Results (acc. to author)

The 6 min electric field strength that the female workers were exposed to was 64.0 +/- 25.2 V/m (mean +/- standard deviation), which exceeded 61 V/m, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference root mean square levels for occupational exposure. The mean exposure duration of the female workers was 22.8 +/- 17.8 months (mean +/- standard deviation).
18 workers (18.4%) had abnormal ECGs in the control group compared with 57 workers (25.4%) in the exposed groups; however, this difference was not statistically significant. Sinus arrhythmia was the most common observed change among the female workers (8.2% of the control group and 13.8% of exposed groups).
Although the exposure level to high frequency electromagnetic fields was high and steady, no statistically significant difference in heart rate, duration of the QRS wave, or QTc intervals were observed between the exposed groups and the control group.
The authors concluded that occupational exposure to 27.2 MHz radiofrequency radiation was not the cause of the ECG changes after considering the confounding factors.

Study funded by

Key Project of the National Eleventh-Five Year Research Program of China
National Health Standard Enacting Program of China

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