Parameters influencing auditory fatigue among professionals working in the amplified music sector: noise exposure and individual factors.

OBJECTIVE: Hearing disorders are common among music professionals, as they are frequently exposed to sound levels exceeding 100 dB(A). By assessing auditory fatigue, situations that are deleterious for hearing could be identified, allowing the deployment of preventive measures before permanent impairment occurs. However, little is known about the factors contributing to auditory fatigue. The objective is to determine the exposure parameters most influencing auditory fatigue during occupational exposure to amplified music. DESIGN: Auditory fatigue was defined as variations of both pure tone auditory (ΔPTA) and efferent reflex thresholds (ΔER) during the workday. Noise exposure was monitored and information on the volunteers was gathered using a questionnaire. STUDY SAMPLE: The population consisted of 43 adult volunteers exposed to amplified music (sound, light or stage technicians, security agents, barmen) and 24 unexposed administrative agents. RESULTS: ΔPTA and ΔER were positively correlated with the energy of noise exposure and its stability over time, i.e a steady noise tends to create more auditory fatigue. CONCLUSION: In addition to a global decrease of music levels and a systematic use of hearing protection, our results advocate for the provision of quiet periods within noise exposures as they reduce auditory fatigue accumulation and long-term risks for hearing.

Occupational exposure to metals among battery recyclers in France: Biomonitoring and external dose measurements.

In battery-recycling facilities, exposure to trace elements may occur through inhalation of contaminated dust or vapor emanating from the treatment processes. Exposure of battery-recycling workers to lead has been quite well covered in the literature. In contrast, we lack data on exposure to other elements contained in batteries. The aim of this study was to characterize the exposure of French battery recyclers to multiple elements using biomonitoring and airborne measurements. Eighty-six workers participated in the study. Inhalable metal concentrations were determined for personal airborne samples, and total exposure was determined from pre-shift and post-shift urine samples collected during the working week. In both types of sample, a total of 33 trace elements were measured using inductively coupled plasma mass spectrometry. Results showed battery recyclers to be mostly exposed to Cd, Co, Cr, Li, Mn, Ni, and Pb. Administrative and sorting workers were exposed at lower levels than maintenance, treatment, and dismantling workers. Cd, Co, Li, Mn, and Ni were detected at high levels in air samples, especially near the treatment facilities, with airborne cadmium levels of up to 79.4 µg/m3. Urinary sample analysis indicated exposure to Cd and Co, with levels measured at up to 27.6 and 3.34 µg/g of creatinine, respectively. Concentrations were compared to data reported for e-waste recycling companies. The data presented provide valuable information on exposure to trace elements for workers involved in battery-recycling. They also highlight the need to improve both collective and individual protective measures, which were not sufficient in the participating companies.

Is Urinary Chromium Specific to Hexavalent Chromium Exposure in the Presence of Co-exposure to Other Chromium Compounds? A Biomonitoring Study in the Electroplating Industry.

OBJECTIVES: Electroplating processes are widely used in metal industries to improve the resistance properties of manufactured metal parts. Workers in this industry are potentially exposed both to hexavalent chromium (Cr(VI)) and to other chromium compounds [mostly trivalent chromium (Cr(III))], due to the use of chromic acid baths. The goal of this study was to validate urinary chromium as a Cr(VI) exposure biomarker in the presence of exposure to other chromium compounds. METHODS: A biomonitoring study consisted in monitoring airborne chromium exposure and urinary chromium for one working week in 93 workers from nine electroplating companies. Chromium concentrations were measured in all urinations of each volunteer for the working week. Individual airborne soluble and insoluble Cr(VI) as well as Cr(III) concentrations were measured for all of the shifts of the week. The main statistical analysis consisted in modelling, in a Bayesian framework, the pre- and post-shift urinary chromium as a function of airborne Cr(III) and airborne Cr(VI), taking into account the day of the week and the time of collection of the urines (pre- or post-shift). RESULTS: Preliminary descriptions showed an increase in pre-shift urinary chromium during the working week. The model showed an increase in urinary chromium over the shift related to the shift-specific airborne Cr(VI) concentration as well as an increasing trend over the week and a relationship with the mean weekly Cr(VI) thought to reflect chronic exposure. Taking into account the Cr(VI) exposure, there was no evidence of an effect of Cr(III) exposure on urinary chromium. A biological limit value (BLV) was derived from the French occupational exposure limit for Cr(VI) of 1 µg m-3 and was estimated at between 1.9 and 2.6 µg g-1 creatinine for a urinary sample collected at the end of the shift on the last working day of the week. CONCLUSIONS: In the present context of mixed exposure to Cr(III) and Cr(VI) in electroplating, this study showed that urinary chromium depended only on airborne Cr(VI) concentrations, which justifies using a BLV for assessing workers' exposure. The estimated BLV was close to the recommended French BLV, which is 1.8 µg g-1 creatinine, in the electroplating industry.

Bivariate Left-Censored Measurements in Biomonitoring: A Bayesian Model for the Determination of Biological Limit Values Based on Occupational Exposure Limits.

Biological limit values (BLV) are often determined from the occupational exposure limits (OEL) in modelling biological data obtained on a number of exposed subjects based on measurements of air exposure. In order to obtain such BLVs, biomonitoring studies are conducted collecting simultaneously biological and airborne measurements to these substances in exposed workers. One obstacle in the modelling of such data is the often large number of values below the limit of detection (LOD) for both biological and airborne measurements (left-censored measurements). A second difficulty, which is also a strength, is that multiple measurements are obtained for the same workers, leading to non-independence of the data. In this paper, we propose a statistical method based on Bayesian theory making use of measurements below the LOD for both dependent (biological) and independent (air exposure) data, and taking into account multiple measurements on the same worker. This method relies on the modelling of the airborne exposure measurements using standard random effect models adapted for values below LOD and the simultaneous modelling of the biological measurements assumed to be linearly (on the log scale) related to the airborne exposure while accounting for between-worker variability. This method is validated by a simulation study in which up to 50% of the measurements are censored for both variables in realistic settings. This simulation study shows that the proposed method is uniformly more efficient than the candidate alternative we considered (maximum likelihood estimation; MLE method) that did not make use of a data with airborne measurements below the LOD. When the method is applied on a real biomonitoring data set among electroplating workers exposed to chromium with 54% censored airborne measurements and 20% censored urinary measurements, the slope is steeper when incorporating these data using the proposed Bayesian method leading to different BLV estimations depending on the OEL used.