| Objective:This study aims to investigate distribution characteristics of hearing loss of workers by co-exposure of ototoxic organic solvents and noise in the wooden furniture manufacturing enterprises and printing enterprise,and measure the exposure levels of noise andototoxic organic solvents in workers,and explore the characteristics of hearing loss of workers by co-exposure of ototoxic organic solvents and noise,and dose-response relationship between hearing loss and co-exposure of ototoxic organic solvents and noise.The results of this study will provide the scientific data for the revisions of occupational health and occupational disease diagnosis standards.Methods:In this study,a total of 727 workers from 9 wooden furniture manufacturing enterprises and 13 printing enterprises were selected by the method of cross-sectional survey with convenient sampling.According to the inclusion and exclusion criteria of research objects determined in this study,655 workers were eventually included as the research objects.According to the presence of noise and/or chemical toxicants,the above-mentioned workers were divided into solvent exposure group,noise exposure group and co-exposure group(a total of 487 workers).A total of 168 administrative workers were selected as the control group,who were not exposed to organic solvents,noise(≤75dB(A))and other occupational hazard factors.Among them,those exposed only to organic solvent(<80dB(A))were set as the organic solvent exposure group;Those exposed to noise alone(≥80dB(A))were set as the noise exposure group,and those exposed to organic solvent and noise(≥80dB(A))were set as the co-exposure group.Individual noise exposure levels were measured by using individual noise dosimeter.The concentrations of organic solvents at workplace were measured by using gas chromatography.Pure tone audiometry was performed in an audiometric booth,where baseline noise was 30 dB,and measured by experienced physicians using pure tone audiometers.Hearing thresholds were measured at frequencies of 0.5,1.0,2.0,3.0,4.0,6.0 and 8.0 kHz in both ears.If the data conform to the normal distribution through the normal test,x±s is used to describe it.Median(M)and quartile(IQR§)were used to describe those who did not fit the normal distribution.Kruskal-Wallis H test was used for the analysis on differences of age and length of service among different groups of subjects.The differences on LEX.W and CNE of single organic solvent and organic solvent mixtures in co-exposure group and organic solvents exposure,and the differences on the cumulative exposure levels in different groups,and the differences on frequencies of hearing threshold between left and right ear,speech-frequency hearing threshold and high-frequency hearing threshold using single factor analysis of variance.The chi-square test and Fisher was applied for the analysis of differences of gender,smoking,alcohol consumption,the use of hearing protective equipment,the use of respiratory protective equipment,and use headphones for entertainment,the exceed rate of Em,the rate of hearing loss at all frequencies,the rate of speech-frequency hearing loss,the rate of high-frequency hearing loss,and the OR value of hearing loss at each frequency,the OR value of speech-frequency hearing loss,and the OR value of high-frequency hearing loss among the different groups.The Cochran-Armitage Trend Test was performed for the analysis the dose-response relationship of each frequency hearing loss rate,speech-frequency hearing loss rate,and high-frequency hearing loss rate at different LEX.W and CNE levels;the exposure level and cumulative exposure level of mixed solvents such as benzene,toluene,xylene,ethylbenzene,and the hearing loss rate of each frequency,the speech-frequency hearing loss rate,and the high-frequency hearing loss rate,the co-exposure to noise and organic solvents and hearing loss rate of each frequency,speech-frequency hearing loss rate,and high-frequency hearing loss rate.Univariate and multivariate Logistic regression models were used to determine the effects of age,sex,CNE,organic solvents exposure,smoking,drinking,the use of hearing protection,the use of respiratory protection,the use of headphones for entertainment,and exposure to toluene,xylene,ethylbenzene,and n-hexane on the prevalence of hearing loss.The OR value and 95%confidence interval(95%CI)were used to estimate the risk of hearing loss.The test level α=0.05(bilateral).Results:1.Following the inclusion and exclusion criteria of the research subjects,a total of 655 research subjects were finally recruited including 461 males(70.4%)and 194 females(29.6%).All subjects were divided into 4 groups,including 138 subjects in co-exposure group,152 subjects in organic solvent exposure group,197 subjects in noise exposure group,and 168 subjects in control group.The differences of median age among 4 groups were not found a statistically significant(P=0.552);The length of service of workers in co-exposure group was lower than that in the noise exposure group,and the difference was statistically significant(P<0.05),there was no significant difference between the organic solvent exposure group and the co-exposure group and the noise exposure group(P>0.05);There was no significant difference in sex composition among the three exposure groups.2.Among furniture manufacturing enterprises,the number of people exposed to the noise of wood processing post is the most(27.0%),and the exposure to the noise of oil grinding post(87.6dB(A))and organic solvent(12.258mg/m3)is the most serious;Among the printing enterprises,the number of printing post noise was the most(25.3%),the noise exposure of beer machine post was the most serious(82.8dB(A)),and the exposure of organic solvent of glue loading post was the most serious(15.007mg/m3).3.The average noise exposure level(LEX.W)of workers in the co-exposure group was foud to be 83.71±3.48 dB(A)(80.0-94.8 dB(A)),and the average noise exposure level of workers in organic solvent exposure group was found to be 68.72±3.38dB(A)(54.3-78.0 dB(A));the average noise exposure levels in both of co-exposure group and noise exposure group were higher than that of organic solvent exposure group and the control group,and the differences were found to be statistically significant(P<0.05);No statistically significant difference was found on average noise exposure levels between the co-exposure group and the noise exposure group(P>0.05).4.The higher exposure level of xylene was found to be 13.14 mg/m3 in workers of co-exposure groups,and the higher exposure level of toluene was found to be 9.18 mg/m3 in workers of organic solvent exposure group.The exposure level of toluene,xylene,ethylbenzene and n-hexane was found to be significantly different between the two groups(P<0.05).No significant difference on exposure level of 5 solvents including toluene,xylene,ethylbenzene,n-hexane and benzene was found between the two groups(P>0.05).The over-standard rate oforganic solvents mixture in co-exposure group was higher than that in organic solvent exposure group,but no statistically significant was found(P>0.05).5.At high frequencies(3.0-8.0 kHz),the exposure levels of LEX.W and CNE,the hearing loss rate of workers was found to increase with increasing exposure level of LEX.W and CNE.The speech-frequency hearing loss rate and hearing loss rate of workers at 0.5kHz and 1.0kHz increased with the increase of toluene exposure and cumulative toluene exposure(P<0.05).The hearing loss rate of workers at 0.5kHz and 8.0kHz increased with the increase of accumulated exposure to ethylbenzene(P<0.05).At 0.5kHz,1.0kHz and 8.0kHz,the hearing loss rate and speech-frequency hearing loss rate of workers increased with the increase of exposure amount and cumulative exposure amount of mixed organic solvents(toluene,xylene,ethylbenzene)(P<0.05).No singnificant difference was found between the hearing loss rate and increasing cumulative exposure level of mixed organic solvents when adding exposure level of benzene.6.The average binaural speech-hearing threshold and the average binaural high-frequency hearing threshold of the workers in co-exposure group were found to be higher than that in both of organic solvent exposure group and noise exposure group.A significant difference on average binaural speech hearing threshold was found between workers of co-exposure group and noise exposure group(P<0.05).At 0.5kHz,1.0kHz and 8.0kHz,a significant difference on hearing loss rate was found between co-exposure group and noise exposure group(P<0.05).At 0.5 kHz,the hearing loss OR values of workers in both of co-exposure group and organic solvent exposure group were found to be higher(OR=9.125,OR=5.551,respectively).At 4.0 kHz,the hearing loss OR value of the workers in noise exposure group was found to be high(OR=5.669).At 0.5 kHz,1.0 kHz,2.0 kHz and 8.0 kHz,the speech-frequency hearing loss OR value of workers in co-exposure group was found to be higher than that in both of organic solvent exposure group and noise exposure group.At 4.0-6.0 kHz,the high-frequency hearing loss OR value of workers in co-exposure group was found to be higher than that in both of noise exposure group and organic solvent exposure group.7.The results of multivariate logistic regression indicate the factors including age,CNE organic solvent exposure levels,co-exposure were found significantly correlated with speech-frequency hearing loss.The risk of speech-frequency hearing loss increased by 2.9%(OR:1.029;95%CI:1.009-1.048)when adding 1 yr at age of workers.The risk of speech-frequency hearing loss increased by 3.5%(OR:1.035;95%CI:1.015-1.048)when 1 dB(A)·year adding at CNE.The risk of speech-frequency hearing loss increased by 169.0%(OR:2.690;95%CI:1.902-3.802)comparion between the workers exposed to organic solvents and the workers not exposed to organic solvents.The risk of speech-frequency hearing loss increased by 169.0%(OR:2.690;95%CI:1.902-3.802)comparion between the workers exposed to both organic solvents and noise and the workers who were not.The factors including age and CNE were found to be significantly corelated with high-frequency hearing loss.The risk of high-frequency hearing loss increased by 7.5%(OR:1.075;95%CI:1.052-1.098)when adding 1 yr at age of workers,and the risk of high-frequency hearing loss increased by 3.3%(OR:1.033;95%CI:1.012-1.054)when 1 dB(A)·year adding at CNE.The factors including age,CNE,organic solvent exposure,co-exposure and alcohol consumption were found to be significantly correlated with the high-frequency hearing loss OR value at 8 kHz.The risk of 8 kHz hearing loss increased by 9.0%(OR:1.090;95%CI:1.061-1.119)when adding 1 yr at age of workers.The risk of 8 kHz hearing loss increased by 7.4%(OR:1.074;95%CI:1.044-1.106)when 1 dB(A)·year adding at CNE.The risk of 8 kHz hearing loss increased by 117.6%(OR=2.176;95%CI:1.420-3.336)compsrison between the workers exposed to organic solvents and the workers not exposed to organic solvents.The risk of 8 kHz hearing loss increased by 158.6%(OR:2.586;95%CI:1.902-4.029)compsrison between the workers exposed to both organic solvents and noise and the workers who were not.The risk of 8 kHz hearing loss increased by 81.3%(OR:1.813;95%CI:1.136-2.892)comparison between the worker drink alcohol and the workers not drink alcohol.The multivariate logistic regression analysis indicates that the factors including age and toluene exposure were found to be significantly corelated with speech-frequency hearing loss.The risk of speech-frequency hearing loss increased by 5.9%(OR:1.059;95%CI:1.029-1.090)when adding 1 yr at age of the workers.The risk of speech-frequency hearing loss increased by 306.1%(OR:4.061;95%CI:1.975-8.353)comparison between toluene exposure index Em<1 group and toluene exposure index Em≥1 group.The factors including age and CNE were found to be significantly corelated with high-frequency hearing loss.The risk of high-frequency hearing loss increased by 7.2%(OR:1.072;95%CI:1.041-1.104)when adding 1yr at age of the workers.The risk of high-frequency hearing loss increased by 12.6%(OR:1.126;95%CI:1.102-1.166)when 1 dB(A)·year adding at CNE.The factors including age,CNE,ethylbenzene exposure,and alcohol consumption were found to be significantly correlated with hearing loss at 8.0 kHz.The risk of 8 kHz hearing loss increased by 7.1%(OR:1.071;95%CI:1.034-1.109)when adding 1yr at age of the workers.The risk of 8 kHz hearing loss increased by 3.6%(OR:1.036:95%CI:1.002-1.072)when 1dB(A)·year adding at CNE.The risk of 8 kHz hearing loss increased by 95.5%(OR:1.955;95%CI:1.107-3.452)comparison between ethylbenzene exposure index Em<1 and ethylbenzene exposure index Em≥1.Compared with non-drinking workers,the risk of 8 kHz hearing loss increased by 111.2%(OR:2.112;95%CI:1.145-3.895)comparison between the workers drink alcohol and the workers not drink alcohol.Conclusion:The most severe hearing loss occurred in workers exposed to both organic solvents and noise in this study.High-frequency hearing loss is not only significantly reduced,but also speech-frequency hearing loss is also affected;Multivariate logistic regression analysis indicates that age,CNE,organic solvent exposure and co-exposure were the risk factors for hearing loss. |
PDF Full Text Request