Female workers were recruited from supermarkets near the factories as the unexposed control group.
|Reference group 1||control group: not exposed|
|Group 2||factories with low exposure: < 150 V/m|
|Group 3||factories with high exposure: ≥ 150 V/m|
|Reference group 4||cumulative exposure level: 0 years-V/m|
|Group 5||cumulative exposure level: 0 - 499 years-V/m|
|Group 6||cumulative exposure level: 500 - 999 years-V/m|
|Group 7||cumulative exposure level: ≥ 1000 years-V/m|
180 female operators in shoe fabrics and 349 female workers in supermarkets
No electric fields were detectable in the supermarkets (≥ 1 V/m). The mean electric field strengths in the frequency range from 25 MHz to 30 MHz in the vicinity of the welding machines in the five factories ranged from 51.3 to 368.9 V/m and exceeded the national standard of 25 V/m. The levels of magnetic field strength ranged from 0.02 A/m to 0.06 A/m below the reference values.
The prevalence of neurovegetative symptoms increased with higher electric field exposures. The prevalence of menstrual disorder was 12.0% in the unexposed group, but was significantly increased in the low exposure group < 150 V/m (26.8%) and in the high exposure group ≥ 150 V/m (33.8%). In the groups with cumulative exposure, the prevalence of most neurovegetative symptoms and menstrual abnormalities increased with higher cumulative exposure. No significant associations between adverse reproductive outcomes and occupational exposure were observed among the female workers. Serum progesterone was significantly lower in the exposed groups compared to the control group.
The authors concluded that occupational exposure to electromagnetic fields of plastic welding machines in shoe factories was associated with adverse health effects, including subjective symptoms, menstrual disorder and low level of serum progesterone among female operators.