Efeitos da dupla proteção auditiva na saúde do trabalhador: revisão de literatura / Effects of double hearing protection on occupational health: a literature review / Efectos de la doble protección auditiva en la salud de los trabajadores: revisión de la literatura

O uso da proteção auditiva pode representar uma série de preocupações de segurança quando considerados o treinamento e orientação, os prejuízos à comunicação e o ambiente ocupacional. O objetivo deste estudo foi verificar os benefícios da dupla proteção auditiva em risco de ruído ocupacional. Os artigos científicos de embasamento foram selecionados pelas bases de dados MEDLINE (Pubmed), Lilacs, Scielo, SCOPUS e Web of Science, sem restrição de idioma, período e localização. Foram localizados 197 artigos em que três atenderam aos critérios de admissão desta pesquisa. Os Equipamentos de Proteção Individual (EPIs) exigem controle rigoroso quanto ao seu uso adequado, que por vezes é negligenciado na rotina diária de trabalho. Conclui-se que a modernização e o uso de tecnologias mais seguras tem o intuito de diminuir o impacto da exposição ao ruído, entretanto, as barreiras entre a economia e a adesão pelos trabalhadores ainda precisam ser minimizadas.

Use of hearing protection can raise a series of safety concerns when considering training and guidance, communication impairments, and occupational environment. Hence, this study assessed the benefits of dual hearing protection in occupational noise risk. Scientific articles were selected from the MEDLINE (PubMed), LILACS, SCIELO, SCOPUS, and Web of Science databases, with no language, period, or location restrictions. A total of 197 articles were located, of which three met the inclusion criteria. Proper PPE (Personal Protective Equipment) usage requires strict monitoring, which is sometimes overlooked in the daily work routine. Modernization and use of safer technologies aim to reduce the impact of noise exposure; however, the barriers between the economy and worker adherence still need to be mitigated.

El uso de protección auditiva puede implicar una serie de preocupaciones de seguridad al considerar el entrenamiento y orientación, el daño a la comunicación y el ambiente laboral. El objetivo de este estudio fue determinar los beneficios de la doble protección auditiva en riesgo de ruido laboral. Se seleccionaron los artículos científicos de las bases de datos MEDLINE (PubMed), LILACS, SciELO, Scopus y Web of Science, sin restricciones de idioma, período y ubicación. Se encontraron 197 artículos, de los cuales tres cumplieron con los criterios de inclusión para este estudio. Los equipos de protección individual (EPI) requieren un riguroso control sobre su adecuado uso y, muchas veces, no son utilizados por los trabajadores durante su rutina laboral. Se concluye que la modernización y el uso de tecnologías más seguras pueden reducir el impacto de la exposición al ruido, sin embargo, las barreras entre la economía y el uso de estos equipos por los trabajadores aún necesitan mitigarse.

Perfil das doenças metabólicas na perda auditiva ocupacional / Profile of metabolic damages in occupational hearing loss / Perfil de enfermedades metabólicas en la pérdida auditiva ocupacional

Introdução: O diagnóstico precoce quanto às perdas auditivas é essencial para minimização do impacto social em relação à rotina laboral e na qualidade de vida. Objetivo: Caracterizar a associação entre a perda auditiva em trabalhadores com doenças metabólicas. Método: Estudo transversal retrospectivo de dados secundários de prontuário com o tratamento das doenças metabólicas, os dados foram coletados em duas clínicas de saúde ocupacional (C1 e C2) em Florianópolis - Santa Catarina (Brasil), no período de janeiro de 2020 a dezembro de 2022, considerando exames referenciais a partir do ano de 2005. Os dados foram organizados em planilhas do programa Microsoft Excel® e, posteriormente, exportados e analisados no software MedCalc® Statistical Software versão 22.006. Resultados: Foram analisados dados de 97 pacientes (71 homens e 26 mulheres), expostos ao ruído ocupacional (p = 0,0047), com diagnóstico de ao menos uma doença metabólica (41,20%) e prevalência de medicamentos da classe ATC H (p = 0,0465) e Losartana® (OR = 1,6976). Conclusão: O ruído ocupacional é o principal fator de risco auditivo nas empresas analisadas, e a presença de doença metabólica poderá influenciar em alterações dos limiares auditivos. Para reduzir a vulnerabilidade dessa população, é necessário a promoção, educação e conscientização dos trabalhadores nos aspectos de saúde. (AU)

Introduction: Early diagnosis of hearing loss is essential to minimize the social impact in relation to work routine and quality of life. Objective: Analyze the association between hearing loss in workers and metabolic diseases. Method: Retrospective cross-sectional study of secondary data on the use of medications in metabolic diseases, the data were collected in two occupational health clinics (C1 and C2) in Florianópolis - Santa Catarina (Brazil), from January 2020 to December 2022, considering references from exams from the year 2005. The data were organized in Microsoft Excel® spreadsheets and subsequently exported and analyzed using the MedCalc® statistical software version 22.006. Results: The data of 97 patients (71 men and 26 women) exposed to occupational noise (p = 0.0047), diagnosed with at least one metabolic disease (41.20%) and prevalence of ATC H class medications (p = 0.0465) and Losartan® (OR = 1.6976). Discussion andConclusion: Occupational noise is the main auditory risk factor, and the presence of metabolic disease can influence hearing thresholds. To reduce the vulnerability of this population, it is necessary to promote, raise awareness and educate, using approaches related to health aspects at work. (AU)

Introducción: El diagnóstico precoz de la pérdida auditiva es fundamental para minimizar el impacto social en la rutina laboral y la calidad de vida. Propósito: Analizar la asociación entre pérdida auditiva en trabajadores y enfermedades metabólicas. Metodología: Estudio transversal retrospectivo de datos secundarios sobre el uso de medicamentos en enfermedades metabólicas; Los datos fueron recolectados en dos clínicas de salud ocupacional (C1 y C2) en en Florianópolis - Santa Catarina (Brasil), de enero de 2020 a diciembre de 2022, considerando referencias de exámenes del año 2005. Los datos fueron organizados en hojas de cálculo Microsoft Excel®. y posteriormente exportados y analizados. utilizando el software estadístico MedCalc® versión 22.006. Resultados: Se analizaron los datos de 97 pacientes (71 hombres y 26 mujeres) expuestos a ruido ocupacional (p = 0,0047), diagnosticados con al menos una enfermedad metabólica (41,20%) y prevalencia de medicamentos clase ATC H (p = 0,0465). y Losartan® (OR = 1,6976). Discusión y Conclusión: El ruido ocupacional es el principal factor de riesgo auditivo y la presencia de enfermedad metabólica puede influir en los umbrales auditivos. Para reducir la vulnerabilidad de esta población es necesario promover, sensibilizar y educar utilizando enfoques relacionados con aspectos de salud en el trabajo. (AU)

Vocal Load of University Professors: Preliminary Results

Purpose: To describe the acoustic characteristics of a classroom, voice quality, fatigue, and vocal load of university professors. Methods: Exploratory, observational, longitudinal, and descriptive study with a single group of participants, including vocal monitoring data over two weeks. Acoustic characterization of the classroom, perceptual-auditory evaluation, and acoustic analysis of voice samples were conducted before and after classes. Vocal dosimetry was performed during classes, and the Vocal Fatigue Index (VFI) was assessed at the beginning of each week. Descriptive analysis of the findings was conducted, and randomization test was performed to verify the internal reliability of the judge. Results: All participants reported speaking loudly in the classroom, with the majority reporting vocal changes in the past six months, and only one participant reported a current vocal change. The classroom had acoustical measures and estimations that deviated from established standards. The professors used high vocal intensities during classes. After the classes, an increase in the absolute values of the aggregated data for CAPE-V, jitter, and fundamental frequency was found, varying within the range of normality. Furthermore, there was an observed increase in both post-lesson intensity and VFI when comparing the two-week period. Conclusions: Vocal intensities and VFI were possibly impacted by the acoustics of the classroom. The increase in average VFI between the weeks may be attributed to a cumulative fatigue sensation. Further research with a larger number of participants and in acoustically conditioned classrooms is suggested in order to evaluate collective intervention proposals aimed at reducing the vocal load on teachers.

Objetivo: Describir las características acústicas, calidad vocal, fatiga y carga vocal de profesores universitarios. Métodos: Estudio exploratorio, observacional, longitudinal, descriptivo con un solo grupo de participantes y datos de monitoreo vocal durante dos semanas. Se realizó caracterización acústica de la sala, evaluación auditiva-perceptiva y acústica de muestras de voz antes y después de las clases. Se realizó dosimetría vocal durante las clases y se verificó el Índice de Fatiga Vocal (IFV) en dos semanas. Se realizó un análisis descriptivo de los hallazgos y una prueba de aleatorización para verificar la confiabilidad interna del juez. Resultados: Todos los participantes informaron hablar en voz alta en clase, la mayoría informó cambios vocales en los últimos seis meses y solo uno informó cambios vocales actuales. La sala presentó mediciones y estimaciones acústicas fuera de las normas establecidas. Los profesores utilizaron intensidades vocales altas durante las clases. Hubo un aumento en los valores absolutos de los datos agrupados para CAPE-V, jitter y frecuencia fundamental, variando dentro de los límites normales, después de las clases. La intensidad después de las clases y el IFV, en la comparación entre las dos semanas, mostraron un aumento. Conclusiones: La dosis vocal y el IFV posiblemente se vieron afectados por la acústica del aula. El aumento del IFV medio entre semanas pudo deberse a la sensación de cansancio acumulada. Se sugieren nuevas investigaciones con un mayor número de participantes y que se realicen en la sala acondicionada acústicamente para evaluar propuestas de intervención colectiva, con el objetivo de reducir la carga vocal de los docentes.

Effects of 3.0T magnetic resonance noise on the hearing of children aged 0-12 years with routine hearing protection / 西安交通大学学报(医学版)

Objective To explore the effect of exposure to noise of 3.0T magnetic resonance imaging(MRI)on children's cochlear function.Methods We prospectively recruited 72 children who underwent cranial MRI examination at our hospital from May to November 2018;3M earplugs and sponge mats were used for hearing protection during MRI scanning.Noise level(dBA)of each MRI sequence was detected with a nonmagnetic microphone and a sound level meter.Distortion product otoacoustic emissions(DPOAE)test at 2-7 kHz was performed 24 hours before and 30 minutes after the MRI examination.Paired t-test or Wilcoxon signed-rank test was used to analyze differences in DPOAE amplitude before and after the MRI examination.Results The average noise level of MRI measured in the study was(107.7±3.92)dBA.Compared with that before the MRI examination,the DPOAE amplitude(dB)changed little after the MRI examination;the range of amplitude differences in each age group was as follows:left ear(-0.24-1.10)and right ear(-0.24-0.74)in the 0-1 year-old group;left ear(-0.07-0.59)and right ear(-0.57-0.75)in the 2-5 year-old group;left ear(-0.36-0.44)and right ear(-0.30-0.57)in the 6-12 year-old group.No statistically significant difference was found(correction P＞0.05).Conclusion No potential impact of 3.0T MRI noise on children's cochlear function was observed under routine hearing protection.

Relationship between self-perceived noise intensity and sleep quality in noise-exposed workers—A mediating role of negative emotions / 环境与职业医学

Background Studies on the relationships of environmental noise exposure with negative emotions and sleep quality have long been reported. Self-perceived noise intensity is not only related to environmental noise exposure, but also reflects an individual's susceptibility to noise; however, few studies on self-perceived noise intensity, negative emotions, and sleep quality have been reported, and it is not clear whether negative emotions play a mediating role in the relationship between self-perceived noise intensity and sleep quality. Objective To analyze the mediating role of negative emotions (anxiety, depression, and stress) in the relationship between self-perceived noise intensity and sleep quality in noise-exposed workers, and to provide a scientific basis for addressing psychological problems and sleep quality induced by noise exposure. Methods Stratified cluster sampling was used to select noise-exposed workers from a large equipment manufacturing plant in Chengdu from May to June 2023, and demographic characteristics were investigated using a self-designed general information questionnaire; self-perceived noise intensity was reported by the study subjects as the noise intensity of their workplaces; sleep quality was synthesized from three indicators: night sleep duration, self-perceived sleep quality, and sleep-related symptoms; the Anxiety-Depression-Stress Scale (DASS-21 scale) was used to evaluate anxiety, depression, and stress of a worker. Structural equation modeling was used to analyze the pathways of negative emotions (anxiety, depression, and stress) between self-perceived noise intensity and sleep quality. Results The positive rates of negative emotions were 33.1% (anxiety symptoms, 215/649), 26.0% (depression symptoms, 169/649), and 14.0% (stress symptoms, 91/649), respectively in a total of 649 noise-exposed workers. Self-perceived noise intensity was positively correlated with sleep quality score (r=0.218, P<0.001) and negative emotions (anxiety, depression, and stress) (r=0.167, 0.145, 0.167, P<0.001); sleep quality score was positively correlated with negative emotions (anxiety, depression, and stress) (r=0.512, 0.447, 0.513, P<0.001). The results of path analysis showed that the negative emotions (anxiety, depression, and stress) partially mediated between self-perceived noise intensity and sleep quality (β=0.123，P<0.001). Self-perceived noise intensity was positively correlated with negative emotions and sleep quality, and there was a path of self-perceived noise intensity → negative emotion → sleep quality (P<0.001), and the mediating effect accounted for 42.71%. Conclusion The positive rates of anxiety, depression, and stress are high among the noise-receiving workers in this manufacturing industry, and negative emotions characterized by anxiety, depression, and stress partially mediate the relationship between self-perceived noise intensity and sleep quality.

Hearing loss and its relationship with blood pressure among workers exposed to noise in a brewery / 公共卫生与预防医学

Objective To investigate the health status of workers exposed to noise in a brewery in Beijing and to analyze the relationship between hearing loss and blood pressure. Methods A total of 949 noise-exposed workers in a brewery who participated in occupational health examination were selected as the investigation subjects. A survey was conducted to investigate the pure tone hearing threshold and abnormal blood pressure of the workers with different characteristics, and to analyze the relationship between the two. Results Among the noise-exposed workers, the detection rates of hearing abnormality, hypertension, and increased systolic and diastolic blood pressure were 73.55%, 52.37%, 43.84% and 46.47%, respectively. The detection rates of hearing abnormality, indicators of hypertension, high frequency hearing threshold abnormality and increased binaural high frequency hearing threshold on average in males were higher than those in females (P 0.05), the detection rates of other hearing abnormality, indicators of hypertension, speech frequency hearing threshold abnormality, high frequency hearing threshold abnormality，increased binaural high frequency hearing threshold on average and the weighted value of the better ear's hearing threshold all increased or had an increasing trend with the increase of age or working years (P< 0.05). The detection rates of hypertension in the groups with high frequency hearing threshold abnormality and increased binaural high frequency hearing threshold on average were higher than those in the normal group (P＜0.05). Conclusion The noise-exposed workers in the brewery have hearing impairment, which is related to the occurrence of hypertension. It is recommended to strengthen the publicity and education on noise protection and take protective measures to reduce the occurrence of occupational noise injury.

Occupational health risk assessment of noise in a coal mining enterprise in Shaanxi Province / 公共卫生与预防医学

Objective To evaluate the noise hazard level of a coal mining enterprise, and identify high-risk operation types and people, and to provide a basis for preventing and controlling the health damage caused by noise. Methods A large coal mining enterprise in Shaanxi Province was selected as the research object. The noise monitoring data of the coal mine over the years was used to calculate the noise exposure matrix of each post in the enterprise, and the classification of occupational hazards at workplaces (GBZ/T 229.4-2012) was used to assess the occupational health risk levels. Results Among the 22 noise-exposed positions in the enterprise, the 8-hour working day equivalent sound level in positions of shearer driver, horseshoe driver, crusher driver, shuttle driver, relaxation screen driver, and grading screen driver were all higher than the occupational exposure limit of noise. In 2021, the noise exposure levels of shearer drivers, crusher drivers, and coal-selecting workers were all higher than 90 dB (A), and the occupational hazard level was moderate hazard level. In addition, the noise exposure levels of most other jobs also exceeded the occupational exposure limit. Conclusion The noise hazards in the coal mine industry are mainly concentrated in the posts of the coal mining system, tunneling system, and screening workshop. Among them, the shearer driver, the crusher driver, and the coal preparation workers have higher noise exposure levels. It is recommended to take corresponding noise reduction measures and strengthen the protection level to reduce the noise exposure risk of workers.

Study on the relationship between HSP70 polymorphism and susceptibility to occupational noise-induced hearing loss / 中国职业医学

ObjectiveTo investigate the correlation between genetic polymorphism of heat shock proteins 70 (HSP70) and susceptibility to occupational noise-induced hearing loss (ONIHL). Methods A total of 229 ONIHL workers were selected as the case group and 229 healthy workers with similar age, years of noise exposure, and noise exposure levels were selected as the control group using the case-control study method. Occupational health examinations were conducted on both groups, and peripheral blood of individuals was collected for DNA extraction. The genotypes of three single nucleotide polymorphisms of the HSP70 were detected using the MassArray system. Results The allele frequency distribution of HSP70 rs2227956, rs1043618, and rs1061581 in the control group was in Hardy-Weinberg equilibrium (all P>0.05). The genotype and allele frequency distribution of rs2227956 was significantly different between the two groups (all P<0.05), while no significant difference was found for rs1043618 and rs1061581 (all P>0.05). After adjusting for age, years of noise exposure, individual noise exposure level, smoking, and drinking, individuals with AG and AG+GG genotypes of rs2227956 had a higher risk of ONIHL than those with AA genotype (all P<0.05). The risk of ONIHL was higher in individuals with G allele of rs2227956 than in those with A allele (P<0.05). No correlation was found between rs1043618 and rs1061581 polymorphisms and the risk of ONIHL (all P>0.05). Conclusion The rs2227956 polymorphism of the HSP70 gene is correlated with susceptibility to ONIHL in noise-exposed workers, and the G allele is a risk factor for ONIHL in this population.

Analyzing the monitoring results of occupational hazards in the workplace of key industries in Guangdong Province, 2020-2023 / 中国职业医学

ObjectiveTo understand the monitoring result of occupational hazard in the workplace of key industries in Guangdong Province from 2020 to 2023. Methods The data of occupational hazards in the workplace of 20 key industries in Guangdong Province from 2020 to 2023 were collected from the “Workplace Occupational Hazard Monitoring System” of the Chinese Disease Prevention and Control System subsystem. The monitoring result of occupational hazard factors, occupational health training, occupational health examination, occupational protection, detection of occupational hazardous agents such as dust, chemical substances and noise were analyzed. Results A total of 13 058 enterprises from key industries were recruited as the monitoring subjects in Guangdong Province. There were 290 large-, 1 342 medium-, 7 635 small-, and 3 791 micro-enterprises, with small and micro-enterprises accounting for 58.5% and 29.0% of the total, respectively. A total of 7 542 enterprises exceeded the national standard in the detection of occupational hazards, with a rate of 57.8%. A total of 1 942 517 workers from 13 058 enterprises were recruited, with 835 567 workers were exposed to occupational hazards, with a rate of 43.0%. The rate of occupational health training for enterprise leaders, occupational health management personnel, and workers was 71.9%, 73.8%, and 86.5%, respectively. The abnormal rate of occupational health examinations for workers exposed to noise, dust, and chemical agents was 2.0%, 0.6%, and 1.0%, respectively. The distribution rate of dust masks, anti-poisoning masks or face masks, and noise prevention earplugs or earmuffs was 83.3%, 71.3%, and 77.8%, respectively. The rate of installation of dust prevention facilities, anti-poisoning facilities, and noise prevention facilities was 85.6%, 81.2%, and 50.1%, respectively. The rate of exceeded the national standard of dust, noise in the worksites/types and workplaces showed a decreasing trend year by year (all P<0.01), while the rate of exceeded the national standard of chemical agents in worksites/types and workplaces showed an increasing trend year by year in various occupational hazards (all P<0.01). Conclusion Occupational hazards in the workplace of key industries in Guangdong Province are relatively common. The proportion of workers exposed to occupational hazards is relatively high. It is necessary to further improve the use of noise prevention facilities and protective equipment, strengthen occupational health training for enterprises throughout the province and regularly monitor occupational hazards to reduce the risk of occupational diseases.

Introduction to four kinds of risk-assessment methods for occupational noise-induced hearing loss / 中国职业医学

Noise is a common occupational hazard in workplaces. Long-term exposure to high-intensity noise mainly causes occupational noise-induced hearing loss (ONIHL). The development of ONIHL is irreversible, and there is currently no cure. At present, risk assessment methods based on noise exposure intensities mainly include risk index assessment method, Engineering Professional Council assessment method in United Kingdom (EDC assessment method in UK), National Institute of Occupational Safety and Health assessment method in United State (NIOSH assessment method in US), and International Standardization Organization assessment method (ISO assessment method). However, the risk index assessment method is subjective and does not consider the effectiveness of workers wearing protective equipment. The EDC assessment method in UK defines ONIHL differently from China. The NIOSH assessment method in US and ISO assessment methods have population data sources that deviate from China, which can lead to bias in risk assessment. In the future, it is necessary to further carry out application research on the risk assessment of ONIHL in Chinese noise-exposed workers, compare the applicabilities of various assessment methods, conduct large-sample population epidemiological studies for verification, and fully utilize the risk-prediction function to prevent and control ONIHL.

Study on the relationship between occupational noise exposure and arteriosclerosis in mechanical manufacturing workers / 中国职业医学

ObjectiveTo explore the relationship between the occupational noise exposure and arteriosclerosis in mechanical manufacturing workers. Methods A total of 453 employees of a machinery manufacturing enterprise were selected as the study subjects using the judgment sampling method. The noise exposure levels in their workplaces were measured, and their cumulative noise exposure (CNE) was assessed based on the type of job-noise exposure matrix and occupational hazard exposure history. Pure-tone audiometry was performed on the research subjects, and their brachial-ankle pulse wave velocity (baPWV) was measured. Results The CNE was (91±11) dB(A) per year and the median baPWV was 1 278.0 cm/s in the research subjects. The results of the generalized linear regression model analysis showed that for every one dB(A) per year increase in CNE, the baPWV of the general population increased by 0.20% ［95% confidence interval (CI) 0.10%-0.30%, P<0.01］, with an increase of 0.17% in males (95%CI 0.06%-0.28%, P<0.01) and 0.28% in females (95%CI 0.07%-0.49%, P<0.01). Using the hearing loss as an outcome indicator for high intensity noise exposure, the results showed that baPWV increased by 7.04% (95%CI 2.42%-11.87%, P<0.01) in individuals with bilateral hearing loss, and by 9.84% and 6.53% (95%CI 3.07%-17.07% and 2.13%-11.11%, all P<0.01) in individuals with elevated high-frequency hearing thresholds in both ears and in either ear, respectively. There was no significant association in elevated speech-frequency hearing thresholds and arteriosclerosis (P>0.05). Conclusion Occupational noise exposure may increase the risk of arteriosclerosis.

Analysis on spectrum characteristics of high-intensity noise in key industries in Guangdong Province / 中国职业医学

ObjectiveTo analyze the spectrum distribution characteristics of high-intensity productive noise in key industries in Guangdong Province. Methods A total of 2 806 enterprises in 21 prefecture-level cities in Guangdong Province were selected as the study subjects using the stratified sampling method. On-site investigations were conducted in workplaces. Noise in workplaces and work-sites, and the noise spectrum of the workplaces with sound pressure level ≥85.0 dB(A) were detected. Results The noise of a total of 23 076 workplaces and 20 969 work sites from 30 key industries were monitored. The median (M) and 25th and 75th percentiles (P25, P75) of workplace sound pressure level were 82.3 (78.6, 86.5) dB(A). The rate of the noise exceeded national standard was 30.4%. The sound pressure level M (P25, P75) of work-site was 78.6 (70.0, 83.5) dB(A). The rate of the noise exceeded national standard was 18.0%. Workplace noise and work site noise were positively correlated (Spearman correlation coefficient=0.86, P<0.01). The rate of the noise exceeded national standard was 46.5% in key work sites where the rate of noise exceeded the national standard was ≥25.0%, and corresponding rate of the workplace noise exceeded national standard was 58.1%. The noise spectrum result of 5 636 workplaces sound pressure level>85.0 dB(A) showed that most of the noise source was from grinding machines (441 cases), and the highest average sound pressure level of noise source was from screening machines [93.0 dB(A)]. Cluster analysis results showed that the main noise sources could be divided into three categories, including wideband noise with levels >80.0 dB in all frequency bands except 8 000.0 Hz, medium-high-frequency noise with the highest sound pressure level at 1 000.0, 2 000.0, and 4 000.0 Hz and low frequencies <75.0 dB, and medium-low-frequency noise below 500.0 Hz with sound pressure level >85.0 dB. Conclusion The rate of the noise exceeded national standard in workplace of key industries in Guangdong Province is high, involving a wide range of industries, with high sound pressure levels and obvious spectrum characteristics of corresponding noise sources. Corresponding noise control strategies can be formulated based on different spectrum characteristics and magnitudes.

Interaction of occupational and non-occupational noise exposure leads to high frequency hearing loss / 中国职业医学

ObjectiveTo explore the impact of the interaction between occupational and non-occupational noise exposure on the risk of high-frequency hearing loss (HFHL) in noise-exposed workers. Methods A total of 602 male workers with normal hearing, engaged in an automobile manufacturing company between 2016 and 2018, were selected as the study subjects using the retrospective cohort study method. Pure-tone audiometry and questionnaire surveys were conducted on the workers. The Kaplan-Meier survival analysis and multivariate Cox proportional hazards regression model were used to analyze the interaction between occupational and non-occupational noise exposure and the risk of HFHL in these workers. Results The prevalence of HFHL of the workers was 34.1% in 2020, without any cases of speech frequency hearing loss. Kaplan-Meier survival analysis result showed that the risk of HFHL increased in workers with excessive national occupational noise exposure intensity, self-reported noisy living environments, and both excessive national occupational noise exposure intensity and self-reported noisy living environments (all P<0.01). The results of the Cox proportional hazards model showed that the combined effect of excessive national occupational noise exposure intensity and self-reported noisy living environments [relative risk (RR)=2.40, P<0.01] was higher than the individual effects of excessive national occupational noise exposure intensity (RR=2.09, P<0.01) and self-reported noisy living environments (RR=2.39, P<0.01). There was an antagonistic effect between excessive national occupational noise exposure intensity and self-reported noisy living environments (interaction index <1.00). Conclusion Both occupational and non-occupational noise exposure can increase the risk of HFHL in noise-exposed workers, and there is an interaction between them.

Analysis on comprehensive noise control effects in an automobile engine manufacturing enterprise / 中国职业医学

ObjectiveTo analyze the measures and effects of comprehensive noise control in an automobile engine manufacturing enterprise. Methods An automobile engine manufacturing enterprise with noise exposure work-sites was selected as the research subject. The noise hazard status of the enterprise was investigated. The noise hazard exceeded the national standard in work-sites was comprehensively treated. The treatment effect was analyzed. Results A total of 395 work-sites exposed to noise were detected. Among them, 16 work-sites exceeded the national noise standard, with the rate of 4.1%. The work-sites with noise exceeding the national standard were mainly in the machine workshop and the casting workshop, with normalization of equivalent continuous A-weighted sound pressure level to a nominal eight hours working day (LEX,8h) ranging from 86.8 to 89.2 and 85.2 to 90.2 dB(A), respectively. In addition, the classification of occupational noise exposure of the mold protection group in the casting workshop was level Ⅱ, and classification of occupational noise exposure of other work-sites with excessive national standard was grade Ⅰ. After the enterprise implemented noise control measures such as process reform, equipment replacement, sound insulation, noise reduction, sound absorption, and vibration isolation, the LEX,8h of nine positions were lower than those before rectification ［(86.7±1.1) vs (83.3±1.3) dB(A), P<0.01］. Conclusion The use of comprehensive control measures can achieve the purpose of reducing noise from the sources, and can be used for reference by relevant enterprises with noise hazards.

Research progress on cognitive dysfunction induced by occupational noise and combined exposure to heavy metals / 中国职业医学

Exposure to occupational noise and heavy metals are common occupational hazards in workplaces. Occupational noise exposure not only leads to noise-induced hearing loss but also cognitive dysfunction. Exposure to common heavy metals such as lead, manganese, and cadmium during work is closely related to cognitive dysfunction in workers. Combined exposure to noise and heavy metals is common in workplaces. However, current research on the combined effects of exposure to occupational noise with lead or manganese on workers' cognitive function is not comprehensive or systematic. The method for cognitive dysfunction identification varies, leading to a lack of comparability. And the causality between occupational exposure and cognitive dysfunction in workers has not been clarified. Therefore, studying the cognitive dysfunction due to combined exposure to noise and common heavy metals is of great significance for workers' occupational health. In the future, it is necessary to unify the method for cognitive dysfunction identification and conduct systematic and comprehensive research on the effects, mechanisms, and combined effects of exposure to occupational noise with lead, manganese, cadmium, and other heavy metals on workers' cognitive dysfunction, to ensure the occupational health rights and interests of workers.

The protective effectiveness of hearing protectors for noise-exposed workers and its influencing factors / 中国职业医学

ObjectiveTo explore the protective effect of hearing protectors worn by noise-exposed workers and its influencing factors. Methods A total of 329 occupational noise-exposed workers were selected as the research subjects by judgment sampling method. A questionnaire survey on the use of ear protectors and individual suitability tests was conducted. Intervention was carried out for those whose personal attenuation rating (PAR) did not pass the baseline standard. Results The median (M) and the 25th and 75th percentiles of baseline PAR were 17.0 (5.0, 22.5) dB. The baseline PAR of the workers who were male, aged 25-<35 years, with a working experience of 5-<15 years, with a college degree or above, wearing ear protectors for 5-<15 years, knowing the right way to wear ear protectors, and workers who wore ear protectors correctly during work was relatively high (all P<0.01). The unqualified rate of baseline PAR of the study subjects was 32.8%. The unqualified rate of baseline PAR of workers in automobile manufacturing enterprises was lower than that of workers in plastic enterprises and textile enterprises (9.2% vs 43.6%, and 9.2% vs 50.0%, both P<0.01). The M of the 108 unqualified worker on baseline PAR was improved after intervention (22.0 vs 1.0 dB, P<0.01). The rates of knowing the right way to wear ear protectors, wearing ear protectors correctly during work, and receiving training on wearing ear protectors correctly for the research subjects were 88.1%, 84.8%, and 86.6%, respectively. Workers in automobile manufacturing enterprises and plastic enterprises had higher rates of knowing the right way to wear ear protectors, wearing ear protectors correctly during work, and receiving training on wearing ear protectors correctly than those in textile enterprises (all P<0.01). Conclusion Gender, age, working experience, education level, duration of wearing ear protectors, knowledge and use of ear protectors correctly are influencing factors of the protective effect of ear protectors for noise-exposed workers.

Occupational hazards in sand casting enterprises in Wenling City / 预防医学

Abstract@#To investigate the main occupational hazards of sand casting process enterprises, so as to provide insights into occupational disease prevention and control.@*Methods@#In 2021 and 2022, six typical ferrous metal casting enterprises using sand casting technology in Wenling City, Zhejiang Province were selected to investigate the production processes and equipment, the operation of occupational disease prevention facilities and personal protective equipment. Occupational hazards including silica dust, noise, high temperature and ultraviolet radiation were detected and analyzed.@*Results@#Six sand casting enterprises had not effectively set up and use occupational disease prevention equipment, and some employees had not worn personal protective equipment as required. The participation rate of occupational health examination was 100.00%. Among the 54 silica dust sampling points at the sand mixing, molding, sand falling, shot blasting and mud core drilling positions, the overall dust concentration exceeding the standard rate was 100.00%, and the respiratory dust exceeding the standard rate was 44.44%. Among the 55 noise measurement points at the sand mixing, sand falling, shot blasting, mud core drilling, polishing and blowing positions, 51 exceeded the standard, with a rate of 92.73%. Among the 90 sampling points for melting, painting, polishing, blowing and welding positions, the concentrations of welding fumes, manganese and its compounds, ethyl acetate and other cahmical factors did not exceed the standard. Six ultraviolet radiation measurement points in the welding position and six heat stress measurement points in the melting position did not exceed the standard.@*Conclusion@#The main occupational hazards of sand casting process enterprises in Wenling City are silica dust and noise, and occupational disease prevention and control should be further strengthened.

Recent Progress and Future Directions of Transcranial Electrical Stimulation for Analgesia / 生物化学与生物物理进展

Transcranial electrical stimulation (tES) is a non-invasive neural modulation technique known for its high safety, patient compliance, and portability. It holds promise as a potential non-pharmacological method for analgesia. However, challenges persist in utilizing tES for pain management, including inconsistent research findings and limited understanding of its analgesic mechanisms. Therefore, by summarizing the advances in the analgesic researches employing the 3 primary tES techniques, transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS), we reviewed the analgesic effects on both acute and chronic pain, as well as the neural mechanisms underlying the analgesic effect of each technique. Accumulating evidence suggests that the analgesic effects of tDCS are significant, but studies on analgesic effects of tACS and tRNS remain limited. And the exact mechanisms of pain relief through tES turned out to be not yet well established. Furthermore, we systematically discussed the limitations of analgesia-related studies employing tES techniques across various aspects, involving research design, stimulation protocol formulation, neural response observation, analgesic effect assessment, and safety considerations. To address these limitations and advance clinical translation, we emphasized utilizing promising stimulation techniques and offered practical suggestions for future research endeavors. Specifically, employing numerical simulation of electric field guided by magnetic resonance imaging (MRI) would reduce variability of outcomes due to individual differences in head anatomy. For this purpose, it is advisable to establish standardized head models based on MRI data from the Chinese populations and validate simulated electric field results in tES research to diminish confounding factors concerning anatomy. Meanwhile, novel techniques like multi-site brain stimulation and interferential stimulation (IFS) could broaden the range of stimulation sites in both scope and depth. Multi-site brain stimulation facilitates modulation of entire neural networks, enabling more sophisticated investigations into the complexity of pain. IFS can reach deep brain tissues without invasive surgical procedures, achieving more comprehensive modulation. Regarding neural response observations, establishing a tES-neuroimaging synchronized platform would enable revealing its mechanisms and personalizing protocols based on inter-subject neural response variability detected through recordings. By integrating tES with various neuroimaging techniques, such as functional MRI, electroencephalography (EEG) and magnetoencephalography, into one unified platform, researchers could examine brain activities in baseline before stimulation, dynamic changes in brain activities during stimulation, and sustained brain responses after stimulation. Additionally, collecting finer-grained data on participant characteristics and pain intensity would enhance the sensitivity of future studies. In designing clinical trials to evaluate chronic pain treatments and reporting the results, adopting the six core outcome domain measures recommended by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) could prove beneficial. Lastly, safety considerations can never be overemphasized in future tES studies especially when combining tES with MRI and EEG techniques. These efforts may help to broaden the research scope, reconcile inconsistencies in findings and elucidate the analgesic mechanisms of tES, thus facilitating the development of pragmatic pain management strategies such as combination therapies and home therapies. Ultimately, these suggestions will maximize the clinical application value of tES in pain treatment to achieve pain relief for patients.

The Electroacoustic Performance of Digital Noise Reduction Systems in Commercial Hearing Aids with Malay Speech-Plus-Noise Test Signals (Prestasi Elektroakustik Sistem Pengurangan Hingar Digital dalam Alat Bantu Pendengaran Komersial dengan Isyarat Ujian Pertuturan-Dalam-Bising Bahasa Melayu) / Jurnal Sains Kesihatan Malaysia

@#One of the most frequent complaints of individuals with hearing impairment is listening comfort in noisy environments. In order to improve listening comforts in background noise, digital noise reduction (DNR) systems are incorporated into hearing aids (HAs). Each hearing aid manufacturer has its proprietary algorithm for the DNR system. The amount of attenuation (dB) provided by the DNR system can be quantified using the hearing aid analyser. However, the standard test signals in the hearing aid analyser could not quantify the attenuation of DNR for speech mixed with noise signals. Therefore, this study aimed to (i) develop speech-plus-noise test signals that incorporate Malay sentences and (ii) quantify the efficacy of DNR systems in commercial hearing aids using the newly developed test signals. Six different brands of hearing aids with identical technology but from different manufacturers were subjected to electroacoustic testing utilising newly created Malay speech-in-noise test signals with and without DNR enabled. The total root-meansquare (RMS) gain reduction for each HA was calculated. The results show that the types of noise, the signal-to-noise ratio and the gender of the speaker have a significant effect (p<0.05) on the amount of gain reduction in the HA output as a result of the DNR system in each HA . In conclusion, the newly developed Malay speech-in-noise test signals can be used to verify the efficacy of DNR system in commercial hearing aids.

Effects of long-term noise exposure during sleep on cognitive function and biological clock-related mechanisms in mice / 环境与职业医学

Background Environmental noise pollution is serious, and there are few studies on the effects of long-term noise exposure during sleep on cognitive function and possible biological clock mechanism. Objective To explore the cognitive impairment induced by noise exposure during sleep in mice and possible biological clock mechanism, and to provide a theoretical basis for the protection against noise exposure. Methods Twenty male C57BL/6J mice were randomly divided into a control group and a noise-exposed group, 10 mice in each group. The noise-exposed group was exposed to sleep-period noise using a noise generator for 12 h (08:00–20:00) per day for a total of 30 d. The calibrated noise intensity was set at 90 dB. No intervention was imposed on the control group. At the end of the noise exposure, cognitive function of mice was examined using the new object recognition experiment and the open field test, and the hippocampal tissue damage of mice were evaluated by Nissl staining, ionized calcium binding adaptor molecule 1 (Iba1) immunofluorescence staining, and real-time fluorescence quantitative PCR for inflammatory factors and biological clock genes. Oxidative stress indicators in the hippocampus of mice were also detected by assay kit. Results After noise exposure during sleep period, the results of new object recognition experiment showed that the discrimination index of mice in the noise-exposed group was 0.06±0.04, which was significantly lower than that of the control group (0.65±0.13) (P<0.05). The results of open field test showed that the central activity distance of the noise-exposed group was (242.20±176.10) mm, which was significantly lower than that of the control group, (1548.00±790.30) mm (P < 0.05), and the central activity time of the noise-exposed group was (0.87±0.64) s, which was significantly lower than that of the control group, (6.00±2.86) s (P < 0.05). The Nissl staining results showed that compared with the control group, neurons in the hippocampus of the noise-exposed mice were shrunken, deeply stained, disorganized, and loosely connected. The immunofluorescence results showed that microglia in the hippocampus of the noise-exposed mice were activated and the expression of Iba1 was significantly increased compared with those of the control group (P<0.05). The real-time PCR results of showed that the mRNA levels of the biological clock genes Clock, Per2, and Rev-erbα were significantly increased compared with those of the control group (P<0.05), and the mRNA level of Per1 was significantly decreased compared with that of the control group (P<0.05); and the mRNA levels of IL-18, IL-6, iNOS, and NLRP3 in the hippocampal tissues of mice were significantly increased compared with those of the control group (P<0.05). The results of oxidative stress evaluation showed that compared with the control group, reduced glutathione content was significantly reduced in the noise-exposed group (P<0.001). Conclusion Noise exposure during sleep period can lead to the destabilization of biological clock genes in hippocampal tissues and trigger hippocampal neuroinflammation, which can lead to the activation of microglia and cause cognitive impairment in mice.