[Analysis on outer hair cells hazards from occupational exposure to low frequency electric and magnetic fields and magnetic fields and its related factors].

OBJECTIVE

To explore the function of outer hair cells and its influencing factors in the workers of occupational exposure to low frequency electric and magnetic fields.

METHOD

502 high-strength LF EMFs-exposed workers were taken as the study subjects. The field intensity indicator and noise analyzer were employed for the examination of the electromagnetic energy intensity and noise value at the working sites. Self-administered questionnaires were adopted. Universal hearing screening by distortion product otoacoustic emission (DPOAE) and pure tone audiometry (PTA) were done. 100 workers who had abnormal POAE were taken as the observation group and 100 workers who had normal DPOAE were taken as the control group. The workers need be confirmed with ABR testing when the pure tone threshold of two consecutive frequencies were above 20 dB HL or DPOAE detection in any frequency did not pass. Multiple factor analysis with logistic regression was performed for the risk factors.

RESULT

The average electric power density in job locations was 21-38 KV/m, which was higher than national standard (< 5 kv/m). Average noise-level in job locations was 52-65 dBHL, which was within the standard (< 85 dB(A). Questionnaire presented that low frequency electric and magnetic fields might increase the incidence of headache, insomnia and tinnitus in the observed group. The incidence of abnormal DPOAE was higher in the subjects of the observed group (P < 0.01). At 676, 933, 3616, 5 130, 7253 Hz, the DPOAE amplitudes of the observed group workers were significantly lower than the control group. Multivariate analysis showed that the risk factors of abnormal DPOAE included exposure of EMF, length of service, daily exposure time, conservatory measures might be protective factors.

CONCLUSION

The changes of DPOAE indicated that the exposure to low frequency electric and magnetic fields had a subtle, discreet and localized impairing effects on outer hair cells. Exposure of low frequency electric and magnetic fields, length of service, daily exposure time might be risk factors, conservatory measures might be protective factors.