Feasibility of a daily noise monitoring intervention for prevention of noise-induced hearing loss.

BACKGROUND: Despite the existence of hearing conservation programmes complying with regulatory standards, noise-induced hearing loss (NIHL) remains one of the most prevalent occupational diseases. Compulsory daily monitoring of noise exposure has been associated with decreased NIHL risk. We report on the experience of a voluntary daily noise monitoring intervention among noise-exposed workers. METHODS: Workers at three locations of a metals manufacturing company voluntarily used an in-ear noise monitoring device that could record and download, on a daily basis, the noise exposure inside of their hearing protection. We compared the hearing loss rates (in decibels hearing level/year) in these volunteers to controls from the same company matched for job title, age, gender, race, plant location, and baseline hearing level. RESULTS: Over the follow-up period, 110 volunteers for whom controls could be identified monitored daily noise exposures an average of 150 times per year. Noise exposures inside of hearing protection were lower than ambient noise levels estimated from company records. While there was no significant difference in hearing loss rates between volunteers and controls, volunteers downloading exposures 150 times per year or had less hearing loss than those who downloaded less frequently. CONCLUSION: These results indicate that voluntary daily noise exposure monitoring by workers is feasible and that greater frequency of downloading is associated with less hearing loss. If further development of noise monitoring technology can improve usability and address barriers to daily use, regular self-monitoring of noise exposure could improve the effectiveness of hearing conservation programmes. TRIAL REGISTRATION NUMBER: NCT01714375.

Amustaline-glutathione pathogen-reduced red blood cell concentrates for transfusion-dependent thalassaemia.

Transfusion-dependent thalassaemia (TDT) requires red blood cell concentrates (RBCC) to prevent complications of anaemia, but carries risk of infection. Pathogen reduction of RBCC offers potential to reduce infectious risk. We evaluated the efficacy and safety of pathogen-reduced (PR) Amustaline-Glutathione (A-GSH) RBCC for TDT. Patients were randomized to a blinded 2-period crossover treatment sequence for six transfusions over 8-10 months with Control and A-GSH-RBCC. The efficacy outcome utilized non-inferiority analysis with 90% power to detect a 15% difference in transfused haemoglobin (Hb), and the safety outcome was the incidence of antibodies to A-GSH-PR-RBCC. By intent to treat (80 patients), 12·5 ± 1·9 RBCC were transfused in each period. Storage durations of A-GSH and C-RBCC were similar (8·9 days). Mean A-GSH-RBCC transfused Hb (g/kg/day) was not inferior to Control (0·113 ± 0·04 vs. 0·111 ± 0·04, P = 0·373, paired t-test). The upper bound of the one-sided 95% confidence interval for the treatment difference from the mixed effects model was 0·005 g/kg/day, within a non-inferiority margin of 0·017 g/kg/day. A-GSH-RBCC mean pre-transfusion Hb levels declined by 6·0 g/l. No antibodies to A-GSH-RBCC were detected, and there were no differences in adverse events. A-GSH-RBCCs offer potential to reduce infectious risk in TDT with a tolerable safety profile.

Red blood cells treated with the amustaline (S-303) pathogen reduction system: a transfusion study in cardiac surgery.

BACKGROUND: Nucleic acid-targeted pathogen inactivation technology using amustaline (S-303) and glutathione (GSH) was developed to reduce the risk of transfusion-transmitted infectious disease and transfusion-associated graft-versus-host disease with red blood cell (RBC) transfusion. STUDY DESIGN AND METHODS: A randomized, double-blind, controlled study was performed to assess the in vitro characteristics of amustaline-treated RBCs (test) compared with conventional (control) RBCs and to evaluate safety and efficacy of transfusion during and after cardiac surgery. The primary device efficacy endpoint was the postproduction hemoglobin (Hb) content of RBCs. Exploratory clinical outcomes included renal and hepatic failure, the 6-minute walk test (a surrogate for cardiopulmonary function), adverse events (AEs), and the immune response to amustaline-treated RBCs. RESULTS: A total of 774 RBC unis were produced. Mean treatment difference in Hb content was -2.27 g/unit (95% confidence interval, -2.61 to -1.92 g/unit), within the prespecified equivalence margins (±5 g/unit) to declare noninferiority. Amustaline-treated RBCs met European guidelines for Hb content, hematocrit, and hemolysis. Fifty-one (25 test and 26 control) patients received study RBCs. There were no significant differences in RBC usage or other clinical outcomes. Observed AEs were within the spectrum expected for patients of similar age undergoing cardiovascular surgery requiring RBCs transfusion. No patients exhibited an immune response specific to amustaline-treated RBCs. CONCLUSION: Amustaline-treated RBCs demonstrated equivalence to control RBCs for Hb content, have appropriate characteristics for transfusion, and were well tolerated when transfused in support of acute anemia. Renal impairment was characterized as a potential efficacy endpoint for pivotal studies of RBC transfusion in cardiac surgery.

A comparison of an audiometric screening survey with an in-depth research questionnaire for hearing loss and hearing loss risk factors.

OBJECTIVE: We assessed the reliability of a hearing risk factor screening survey used by hearing conservation programmes for noise-exposed workers. DESIGN: We compared workers' answers from the screening survey to their answers to a confidential research questionnaire regarding hearing loss risk factors. We calculated kappa statistics to test the correlation between yes/no questions in the research questionnaire compared to answers from 1 and 5 years of screening surveys. STUDY SAMPLE: We compared the screening survey and research questionnaire answers of 274 aluminum plant workers. RESULTS: Most of the questions in the in-company screening survey showed fair to moderate agreement with the research questionnaire (kappa range: -0.02, 0.57). Workers' answers to the screening survey had better correlation with the research questionnaire when we compared 5 years of screening answers. For nearly all questions, workers were more likely to respond affirmatively on the research questionnaire than the screening survey. CONCLUSIONS: Hearing conservation programmes should be aware that workers may underreport hearing loss risk factors and functional hearing status on an audiometric screening survey. Validating company screening tools could help provide more accurate information on hearing loss and risk factors.

Does tinnitus, hearing asymmetry, or hearing loss predispose to occupational injury risk?

OBJECTIVE: To determine the relative contributions of tinnitus, asymmetrical hearing loss, low frequency hearing loss (pure tone average of 0.5, 1, 2, 3 kHz; PTA.5123), or high frequency hearing loss (pure tone average of 4, 6 kHz; PTA46), to acute injury risk among a cohort of production and maintenance workers at six aluminum manufacturing plants, adjusting for ambient noise exposure and other recognized predictors of injury risk. DESIGN: Retrospective analysis. STUDY SAMPLE: The study considered 9920 workers employed during 2003 to 2008. The cohort consisted of 8818 workers (89%) whose complete records were available. RESULTS: Adjusting for noise exposure and other recognized injury predictors, a 25% increased acute injury risk was observed among workers with a history of tinnitus in conjunction with high-frequency hearing loss (PTA46). Low frequency hearing loss may be associated with minor, yet less serious, injury risk. We did not find evidence that asymmetry contributes to injury risk. CONCLUSION: These results provide evidence that tinnitus, combined with high-frequency hearing loss, may pose an important safety threat to workers, especially those who work in high-noise exposed environments. These at risk workers may require careful examination of their communication and hearing protection needs.

The dose-response relationship between in-ear occupational noise exposure and hearing loss.

OBJECTIVES: Current understanding of the dose-response relationship between occupational noise and hearing loss is based on cross-sectional studies prior to the widespread use of hearing protection, and with limited data regarding noise exposures below 85 dBA. We report on the hearing loss experience of a unique cohort of industrial workers, with daily monitoring of noise inside of hearing protection devices. METHODS: At an industrial facility, workers exhibiting accelerated hearing loss were enrolled in a mandatory programme to monitor daily noise exposures inside of hearing protection. We compared these noise measurements (as time-weighted LAVG) to interval rates of high-frequency hearing loss over a 6-year period using a mixed-effects model, adjusting for potential confounders. RESULTS: Workers' high-frequency hearing levels at study inception averaged more than 40 dB Hearing threshold level (HTL). Most noise exposures were less than 85 dBA (mean LAVG 76 dBA, IQR 74-80 dBA). We found no statistical relationship between LAvg and high-frequency hearing loss (p=0.53). Using a metric for monthly maximum noise exposure did not improve model fit. CONCLUSIONS: At-ear noise exposures below 85 dBA did not show an association with risk of high-frequency hearing loss among workers with substantial past noise exposure and hearing loss at baseline. Therefore, effective noise control to below 85 dBA may lead to significant reduction in occupational hearing loss risk in such individuals. Further research is needed on the dose-response relationship of noise and hearing loss in individuals with normal hearing and little prior noise exposure.

Impact of daily noise exposure monitoring on occupational noise exposures in manufacturing workers.

OBJECTIVE: Despite the use of hearing protection devices (HPDs), noise induced hearing loss (NIHL) remains one of the most prevalent occupational conditions. A new technology allows for daily monitoring of noise exposures under HPDs. We report on an intervention employing the voluntary use of this technology in a worksite setting. DESIGN: Volunteers were fitted with a device allowing them to monitor noise exposure under their hearing protection on a daily basis. The trends in noise exposures for individuals who completed at least six months of the intervention were analysed. STUDY SAMPLE: Recruitment occurred at three manufacturing facilities, with 127 workers enrolling and 66 workers actively using the device during their work shifts. RESULTS: Among volunteers downloading regularly, the percentage of daily exposures in excess of the OSHA action level (85 dBA) decreased from 14% to 8%, while the percentage of daily exposures in excess of 90 dBA decreased from 4% to less than 2%. CONCLUSION: Initial results from this longitudinal study indicate that volunteers find daily noise exposure monitoring to be feasible, and that workers who monitor daily are able to reduce exposures. The results of subject adherence shed light on the challenges and possibilities of worksite interventions for health and safety.

Tracking occupational hearing loss across global industries: a comparative analysis of metrics.

Occupational hearing loss is one of the most prevalent occupational conditions; yet, there is no acknowledged international metric to allow comparisons of risk between different industries and regions. In order to make recommendations for an international standard of occupational hearing loss, members of an international industry group (the International Aluminium Association) submitted details of different hearing loss metrics currently in use by members. We compared the performance of these metrics using an audiometric data set for over 6000 individuals working in 10 locations of one member company. We calculated rates for each metric at each location from 2002 to 2006. For comparison, we calculated the difference of observed-expected (for age) binaural high-frequency hearing loss (in dB/year) for each location over the same time period. We performed linear regression to determine the correlation between each metric and the observed-expected rate of hearing loss. The different metrics produced discrepant results, with annual rates ranging from 0.0% for a less-sensitive metric to more than 10% for a highly sensitive metric. At least two metrics, a 10dB age-corrected threshold shift from baseline and a 15dB nonage-corrected shift metric, correlated well with the difference of observed-expected high-frequency hearing loss. This study suggests that it is feasible to develop an international standard for tracking occupational hearing loss in industrial working populations.

Effect of daily noise exposure monitoring on annual rates of hearing loss in industrial workers.

OBJECTIVES: Occupational noise-induced hearing loss (NIHL) is prevalent, yet evidence on the effectiveness of preventive interventions is lacking. The effectiveness of a new technology allowing workers to monitor daily at-ear noise exposure was analysed. METHODS: Workers in the hearing conservation program of an aluminium smelter were recruited because of accelerated rates of hearing loss. The intervention consisted of daily monitoring of at-ear noise exposure and regular feedback on exposures from supervisors. The annual rate of change in high frequency hearing average at 2, 3 and 4 KHz before intervention (2000-2004) and 4 years after intervention (2006-2009) was determined. Annual rates of loss were compared between 78 intervention subjects and 234 controls in other company smelters matched for age, gender and high frequency hearing threshold level in 2005. RESULTS: Individuals monitoring daily noise exposure experienced on average no further worsening of high frequency hearing (average rate of hearing change at 2, 3 and 4 KHz = -0.5 dB/year). Matched controls also showed decelerating hearing loss, the difference in rates between the two groups being significant (p < 0.0001). Analysis of a subset of intervention subjects matched to controls for initial rate of hearing loss showed a similar trend but the difference was not statistically significant (p = 0.06). CONCLUSION: Monitoring daily occupational noise exposure inside hearing protection with ongoing administrative feedback apparently reduces the risk of occupational NIHL in industrial workers. Longer follow-up of these workers will help determine the significance of the intervention effect. Intervention studies for the prevention of NIHL need to include appropriate control groups.

Assessing Hearing Conservation Program Effectiveness: Results of a Multisite Assessment.

OBJECTIVES: Noise-induced hearing loss (NIHL) remains one of the most prevalent occupational diseases. Occupational hearing conservation programs (HCPs) can reduce the risk of NIHL, but there remains no consensus on assessing HCP effectiveness. We conducted a multisite, mixed-method assessment of HCP programs. METHODS: At 13 manufacturing plants, we performed assessments, including interviews with program staff and worker focus groups and surveys. We analyzed the association between these assessments and age-corrected NIHL rates. RESULTS: Only a few items from the HCP staff interviews correlated with NIHL rates. For the employee survey, management commitment to NIHL prevention and being counseled about NIHL were strongly associated with NIHL rates. CONCLUSION: Management commitment and counseling of workers about NIHL may be key factors in program effectiveness. A combination of qualitative and quantitative methods appears to be useful for assessing HCPs.

Audiometric "early flags" for occupational hearing loss.

OBJECTIVE: OSHA criteria for recording occupational noise-induced hearing loss (NIHL) do not ensure early detection, yet scientific consensus is lacking regarding optimal "early flags" for NIHL. This study compares early flag metrics to the subsequent development of recordable hearing loss. METHODS: In a longitudinal analysis of industrial audiograms, we calculated time from flag event to recordable hearing loss as well as 10 year risk of recordable hearing loss following flag occurrence. RESULTS: The 10 dB non-age-corrected STS and the 8 dB age-corrected shift at 2, 3, and 4 kHz optimally combined positive predictive value and length of time to recordable hearing loss. CONCLUSIONS: Professionals supervising audiometric surveillance must balance predictive value of early flags with timeliness of detection. This study provides a framework for validation and selection of audiometric early flags in hearing conservation settings.

Association between ambient noise exposure, hearing acuity, and risk of acute occupational injury.

OBJECTIVE: This study aimed to examine the associations between acute workplace injury risk, ambient noise exposure, and hearing acuity, adjusting for reported hearing protection use. METHODS: In a cohort of 9220 aluminum manufacturing workers studied over six years (33 300 person-years, 13 323 person-jobs), multivariate mixed effects models were used to estimate relative risk (RR) of all injuries as well as serious injuries by noise exposure category and hearing threshold level (HTL) adjusting for recognized and potential confounders. RESULTS: Compared to noise <82 dBA, higher exposure was associated with elevated risk in a monotonic and statistically significant exposure-response pattern for all injuries and serious injuries with higher risk estimates observed for serious injuries [82-84.99 dBA: RR 1.26, 95% confidence interval (95% CI) 0.96-1.64; 85-87.99 dBA: RR 1.39, 95% CI 1.05-1.85; ≥88 dBA: RR 2.29, 95% CI 1.52-3.47]. Hearing loss was associated with increased risk for all injuries, but was not a significant predictor of risk for the subset of more serious injuries. Compared to those without hearing loss, workers with HTL ≥25 dB had 21% increased all injury risk (RR 1.21, 95% CI 1.09-1.33) while those with HTL 10-24.99 dB had 6% increased risk (RR 1.06, 95% CI 1.00-1.13). Reported hearing protection type did not predict injury risk. CONCLUSION: Noise exposure levels as low as 85 dBA may increase workplace injury risk. HTL was associated with increased risk for all, but not the subset of serious, injuries. Additional study is needed both to confirm the observed associations and explore causal pathways.

Impact of OSHA final rule--recording hearing loss: an analysis of an industrial audiometric dataset.

The 2003 Occupational Safety and Health Administration (OSHA) Occupational Injury and Illness Recording and Reporting Final Rule changed the definition of recordable work-related hearing loss. We performed a study of the Alcoa Inc. audiometric database to evaluate the impact of this new rule. The 2003 rule increased the rate of potentially recordable hearing loss events from 0.2% to 1.6% per year. A total of 68.6% of potentially recordable cases had American Academy of Audiology/American Medical Association (AAO/AMA) hearing impairment at the time of recordability. On average, recordable loss occurred after onset of impairment, whereas the non-age-corrected 10-dB standard threshold shift (STS) usually preceded impairment. The OSHA Final Rule will significantly increase recordable cases of occupational hearing loss. The new case definition is usually accompanied by AAO/AMA hearing impairment. Other, more sensitive metrics should therefore be used for early detection and prevention of hearing loss.

Particle Size Distribution in Aluminum Manufacturing Facilities.

As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 µm in smelters vs. 1.31 µm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001). Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities.

Development of a job-exposure matrix for exposure to total and fine particulate matter in the aluminum industry.

Increasing evidence indicates that exposure to particulate matter (PM) at environmental concentrations increases the risk of cardiovascular disease, particularly PM with an aerodynamic diameter of less than 2.5 µm (PM(2.5)). Despite this, the health impacts of higher occupational exposures to PM(2.5) have rarely been evaluated. In part, this research gap derives from the absence of information on PM(2.5) exposures in the workplace. To address this gap, we have developed a job-exposure matrix (JEM) to estimate exposure to two size fractions of PM in the aluminum industry. Measurements of total PM (TPM) and PM(2.5) were used to develop exposure metrics for an epidemiologic study. TPM exposures for distinct exposure groups (DEGs) in the JEM were calculated using 8385 personal TPM samples collected at 11 facilities (1980-2011). For eight of these facilities, simultaneous PM(2.5) and TPM personal monitoring was conducted from 2010 to 2011 to determine the percent of TPM that is composed of PM(2.5) (%PM(2.5)) in each DEG. The mean TPM from the JEM was then multiplied by %PM(2.5) to calculate PM(2.5) exposure concentrations in each DEG. Exposures in the smelters were substantially higher than in fabrication units; mean TPM concentrations in smelters and fabrication facilities were 3.86 and 0.76 mg/m(3), and the corresponding mean PM(2.5) concentrations were 2.03 and 0.40 mg/m(3). Observed occupational exposures in this study generally exceeded environmental PM(2.5) concentrations by an order of magnitude.

Winter depression and diabetes.

Depression is a common and often harmful disorder, which is frequently associated with the winter season. Research has shown a link between type 2 diabetes mellitus and depression. Furthermore, diabetics with depression have a higher rate of adverse outcomes. Little has been published regarding the seasonality of depression in diabetics. The case report described in this article concerns a 65-year-old woman with type 2 diabetes and a history of winter depression. Current evidence-based management options are reviewed.

Trends in the prevalence of hearing loss among young adults entering an industrial workforce 1985 to 2004.

OBJECTIVES: Studies have suggested that hearing loss due to recreational noise exposure may be on the rise among adolescents and young adults. This study examines whether the hearing status of young US adults entering an industrial workforce has worsened over the past 20 yr. DESIGN: The baseline audiograms of 2526 individuals ages 17 to 25 beginning employment at a multisite US corporation between 1985 and 2004 were analyzed to determine the yearly prevalence of hearing loss. RESULTS: Approximately 16% of the young adults in the sample had high frequency hearing loss (defined as hearing thresholds greater than 15 dB in either ear at 3,4, or 6 kHz). In a linear regression model, this prevalence decreased over the 20-yr period (odds ratio (OR) = 0.96, 95% confidence interval (CI): 0.94, 0.99). Almost 20% of subjects had audiometric "notches" consistent with noise exposure; this rate remained constant over the 20 yr, as did the prevalence (5%) of low frequency hearing loss. CONCLUSIONS: These results indicate that despite concern about widespread recreational noise exposures, the prevalence of hearing loss among a group of young US adults has not significantly increased over the past two decades.

Audiogram notches in noise-exposed workers.

OBJECTIVES: Diagnostic criteria for noise-induced hearing loss include the audiometric notch, yet no standardized definition exists. This study tested whether objective notch metrics could match the clinical judgments of an expert panel. DESIGN: A panel of occupational physicians, otolaryngologists, and audiologists reviewed audiograms of noise-exposed workers. In a two-sample process, the panel judged whether a notch was present and whether hearing loss had progressed in a notch pattern. Quantitative notch metrics were compared against expert decisions. RESULTS: At least five of six experts agreed about notch identification in 71 and 72% of the cases in the two samples, and agreement about notch progression was 61 and 67%. Notch depth and professional specialty appeared to affect notch judgments. Despite this variability, a notch metric showed excellent agreement with expert notch consensus in each sample (94.7 and 96.6%; kappa = 0.88 and 0.92). CONCLUSIONS: Audiogram notch metrics can agree with expert clinical consensus and assist in the surveillance of noise-exposed workers.

Development of a new standard laboratory protocol for estimation of the field attenuation of hearing protection devices: sample size necessary to provide acceptable reproducibility.

The mandate of ASA Working Group S12/WG11 has been to develop "laboratory and/or field procedure(s) that yield useful estimates of field performance" of hearing protection devices (HPDs). A real-ear attenuation at threshold procedure was selected, devised, tested for one earmuff and three earplugs via an interlaboratory study involving five laboratories and 147 subjects, and incorporated into a new standard that was approved in 1997 [Royster et al., "Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S 12, Noise," J. Acoust. Soc. Am. 99, 1506-1526; ANSI, S12.6-1997, "American National Standard method for measuring real-ear attenuation of hearing protectors" (American National Standards Institute, New York, 1997)]. The subject-fit methodology of ANSI S12.6-1997 relies upon listeners who are audiometrically proficient, but inexperienced in the use of HPDs. Whenever a new method is adopted, it is important to know the effects of variability on the power of the measurements. In evaluation of protector noise reduction determined by experimenter-fit, informed-user-fit, and subject-fit methods, interlaboratory reproducibility was found to be best for the subject-fit method. Formulas were derived for determining the minimum detectable difference between attenuation measurements and for determining the number of subjects necessary to achieve a selected level of precision. For a precision of 6 dB, the study found that the minimum number of subjects was 4 for the Bilsom UF-1 earmuff, 10 for the E.A.R Classic earplug, 31 for the Willson EP100 earplug, and 22 for the PlasMed V-51R earplug.