Effect of co-exposure of low-level benzene derivatives and noise on hearing loss of workers / 中国职业医学

ABSTRACT

OBJECTIVE: To explore the effects of combined exposure to low-level benzene derivatives and noise on hearing loss of workers. METHODS: A total of 216 employees from nine wood furniture factories and four printing factories were selected as research subjects by typical sampling method. Those without exposure to occupational hazardous factors were set as the control group, those exposed to noise alone were set as the noise group, and those exposed to benzene derivatives and noise were set as the combined exposure group. The normalization of equivalent continuous A-weighted sound pressure level to a nominal 8 hours working day(L_(EX,8 h)) and the exposure concentration of time weighted average(C_(TWA)) of benzene, toluene, xylene, ethylbenzene in the workplace air of the three groups were detected, and the hearing threshold of 0.5-8.0 kHz in both ears of the research subjects were measured by pure tone audiometry. RESULTS: No benzene was detected in the workplace air of the combined exposure group, and the C_(TWA) of toluene, xylene and ethylbenzene were all lower than the occupational exposure limits. The L_(EX,8 h) of the noise group and combined exposure group were all higher than that of the control group [(85.6±2.5) vs(68.7±4.4) dB(A),(84.3±3.1) vs(68.7±4.4) dB(A), all P<0.05], while the L_(EX,8 h) of the noise group was higher than that of the combined exposure group [(85.6±2.5) vs(84.3±3.1) dB(A), P<0.05]. Compared with the control group, the individual frequency hearing thresholds, average hearing threshold of speech frequency and average hearing threshold of high frequency in both ears in the noise group and the combined exposure group were increased(all P<0.05), and the detection rates of speech frequency hearing loss and high frequency hearing loss were increased(all P<0.02). The hearing thresholds of right ear of 0.5, 1.0 kHz and left ear of 0.5 kHz were increased in the combined exposure group(all P<0.05), and the detection rate of speech frequency hearing loss was increased(16.7% vs 40.8%, P<0.02), when compared with the noise group. Multivariate logistic regression analysis results showed that the risk of speech frequency hearing loss and high frequency hearing loss in the combined exposure group were higher than that in the control group and the noise group(all P<0.05), after excluding the influence of confounding factors such as education level and smoking.CONCLUSION: The combined exposure to low-level benzene derivatives and noise may have a synergistic effect on the hearing loss in workers.