Polycyclic aromatic hydrocarbon exposure and DNA oxidative damage of workers in workshops of a petrochemical group

The petrochemical industry has promoted the development of economy, while polycyclic aromatic hydrocarbons (PAHs) produced by the industry become the threat for environment and humans. Data on human occupational exposure in petrochemical industry are limited. In the present study, urinary hydroxylated PAH metabolites (OH-PAHs) and a biomarker of DNA oxidative damage (8-hydroxy-2'-deoxyguanosine (8-OHdG)) were measured in 546 workers of a petrochemical group in Northeast China, to investigate PAH exposure and related potential health risk. The concentrations of ∑₉OH-PAH in all workers were 0.25-175 μg/g Cre with a median value of 4.41 μg/g Cre. Metabolites of naphthalene were the predominant compounds. The levels of PAH metabolites were significantly different for workers with different jobs, which were the highest for recycling workers (13.7 μg/g Cre) and the lowest for agency managers (5.12 μg/g Cre). Besides, higher levels of OH-PAHs were usually found in males and older workers. There was a dose-response relationship between levels of 8-OHdG and ∑₉OH-PAHs (p < 0.01). No difference was observed in concentrations of 8-OHdG for workers of different gender or ages, work history as well as noise. Furthermore, workers simultaneously exposed to other potential pollutants and higher levels of ∑₉OH-PAH had significantly higher levels of 8-OHdG compared with those in the corresponding subgroups. Our results suggested that exposure to PAHs or co-exposure to PAHs and potential toxics in the petrochemical plant may cause DNA damage. We call for more researches on the associations among noise, chemical pollution and oxidative stress to workers in the real working environment.

A Bayesian network model to predict the role of hospital noise, annoyance, and sensitivity in quality of patient care

Background

Hospital noise can adversely impact nurses’ health, their cognitive function and emotion and in turn, influence the quality of patient care and patient safety. Thus, the aim of this study was to predict the contributing roles of exposure to hospital noise, staff noise-sensitivity and annoyance, on the quality of patient care.

Methods

This descriptive and cross-sectional study was carried out among nurses in an Iranian hospital. To determine nurses’ noise exposure level, the noise was measured in 1510 locations across the hospital in accordance with ISO 9612 standards using KIMO DB 300/2 sound level meter and analyzer. An online survey was used to collect nurses’ individual data. Study questionnaires included demographics, Weinstein noise sensitivity scale, noise annoyance scale, and quality of patient care scale. Finally, to analyze the data, Bayesian Networks (BNs), as probabilistic and graphical models, were used.

Results

For the high noise exposure state, high noise sensitivity, and high annoyance, with the probability of 100%, the probability of delivering a desirable quality of patient care decreased by 21, 14, and 23%, respectively. Moreover, at the concurrently high noise exposure and high noise sensitivity with the probability of 100%, the desirable quality of patient care decreased by 26%. The Bayesian most influence value was related to the association of noise exposure and annoyance (0.636). Moreover, annoyance had the highest association with the physical aspect of quality of care (0.400) and sensitivity had the greatest association with the communication aspect (0.283).

Conclusion

Annoyance induced from environmental noise and personal sensitivity affected the quality of patient care adversely. Moreover, noise and sensitivity had a separate direct adverse effect upon the quality of patient care, and their co-occurrence reduced the potential for delivering quality patient care.

Embryonic medial ganglionic eminence cells survive and integrate into the inferior colliculus of adult mice

Acoustic overexposure can lead to decreased inhibition in auditory centers, including the inferior colliculus (IC), and has been implicated in the development of central auditory pathologies. While systemic drugs that increase GABAergic transmission have been shown to provide symptomatic relief, their side effect profiles impose an upper-limit on the dose and duration of use. A treatment that locally increases inhibition in auditory nuclei could mitigate these side effects. One such approach could be transplantation of inhibitory precursor neurons derived from the medial ganglionic eminence (MGE). The present study investigated whether transplanted MGE cells can survive and integrate into the IC of non-noise exposed and noise exposed mice. MGE cells were harvested on embryonic days 12-14 and injected bilaterally into the IC of adult mice, with or without previous noise exposure. At one-week post transplantation, MGE cells possessed small, elongated soma and bipolar processes, characteristic of migrating cells. By 5 weeks, MGE cells exhibited a more mature morphology, with multiple branching processes and axons with boutons that stain positive for the vesicular GABA transporter (VGAT). The MGE survival rate after 14 weeks post transplantation was 1.7% in non-noise exposed subjects. MGE survival rate was not significantly affected by noise exposure (1.2%). In both groups the vast majority of transplanted MGE cells (>97%) expressed the vesicular GABA transporter. Furthermore, electronmicroscopic analysis indicated that transplanted MGE cells formed synapses with and received synaptic endings from host IC neurons. Acoustic stimulation lead to a significant increase in the percentage of endogenous inhibitory cells that express c-fos but had no effect on the percentage of c-fos expressing transplanted MGE cells. MGE cells were observed in the IC up to 22 weeks post transplantation, the longest time point investigated, suggesting long term survival and integration. These data provide the first evidence that transplantation of MGE cells is viable in the IC and provides a new strategy to explore treatment options for central hearing dysfunction following noise exposure.

Noise exposure and risk of myocardial infarction incidence and mortality: a dose-response meta-analysis

The strength and shape of the dose-response relationship between different types of noise and myocardial infarction (MI) remain unclear. Therefore, we aimed to summarize the evidence of the association between various types of noise and MI incidence and mortality through a dose-response meta-analysis. We performed a systematic search of the PubMed, Embase, and Web of Science databases up to December 19, 2021. The generalized least-squares method and restricted cubic splines were used to assess the potential linear and nonlinear dose-response relationships between noise exposure and the risk of MI events. Twenty observational studies with 34 reports met the eligibility criteria. In the linear models, the pooled relative risk and corresponding 95% confidence interval (CI) for MI incidence was 1.04 (95% CI: 1.02 - 1.05), and the MI mortality was 1.02 (95% CI: 1.02 - 1.03) for each 10 dB(A) increase in noise exposure. In addition, we observed an approximately J-shaped dose-response relationship between noise and MI mortality (P_nonlinearity = 0.0037), whereas the threshold for the statistical impact of noise on MI mortality may be 42 dB(A). Our findings support the notion that various types of noise exposure have a positive dose-response relationship with the risk of MI incidence and mortality.

A forskolin-loaded nanodelivery system prevents noise-induced hearing loss

Hearing loss is the most common sensory disorder worldwide and may result from age, drugs, or exposure to excessive noise. Crossing the blood-labyrinth barrier to achieve targeted drug delivery to the inner ear is key to the treatment of hearing loss. We designed a nanoparticle (NP)-based system for targeted drug delivery of forskolin (FSK) to the inner ear, driven by the prestin-targeting peptide LS19 ("ligand-receptor type interaction"). In vivo experiments in developing zebrafish embryos (4-96 h past fertilization) and mice confirmed that LS19-FSK specifically targeted and accumulated in zebrafish lateral line neuromasts and mouse outer hair cells (OHCs). LS19 peptide modification enabled LS19-FSK-NPs to rapidly target OHCs with high specificity. Furthermore, the multifunctional LS19-FSK-NPs were successfully delivered to the OHCs via the round window membrane route and exhibited slow-release properties. The sustained release and intracellular accumulation of FSK inhibited apoptosis of OHCs. Compared with LS19-NPs and FSK-NPs, LS19-FSK-NPs provided significantly stronger protection against noise-induced hearing damage, based on auditory brainstem responses at 4, 8, 16, and 32 kHz. Thus, our specially designed targeted nano-delivery system may serve as a basis for future clinical applications and treatment platforms and has the potential to significantly improve the treatment results of many inner ear diseases.

Annoyance due to residential road traffic and aircraft noise: Empirical evidence from two European cities

Based on a study in two European cities, Mainz in Germany and Zurich in Switzerland, the article investigates both acoustical and non-acoustical factors affecting indoor annoyance due to residential road traffic and aircraft noise. We specifically focus on three factors: (1) the role of windows as a feature of the building where people live; (2) the role of individual environmental concern as a general attitude; and (3) the role of household income as an indicator of socioeconomic resources. Empirical results show that closed windows in general and closed high-quality windows in particular are an important barrier against outdoor road traffic and aircraft noise, as well as a helpful subjective coping tool against corresponding annoyances. Environmental concern, too, proves to be a significant predictor of noise annoyance. Environmentally highly concerned people articulate feelings of annoyance more often than environmentally less concerned ones. As expected income is negatively related to road traffic noise annoyance. However, we find a positive association of income with annoyance from aircraft noise. Although objective exposure to aircraft noise is lower for high-income households, they feel stronger annoyed by noise from airplanes. Income shows various indirect effects on noise annoyance. A comparative analysis of road traffic and aircraft noise annoyance yields similarities, but also remarkable differences in terms of their influence factors.

Association between community noise and children's cognitive and behavioral development: A prospective cohort study

BACKGROUND

Noise exposure has been associated with adverse cognitive and behavioral outcomes in children, but evidence on longitudinal associations between community noise and child development in low- and middle-income countries is rare. We investigated associations between community noise and behavioral and cognitive development in preschool children in São Paulo.

METHODS

We linked child development data from the São Paulo Western Region Birth Cohort with average (Lden) and night-time (Lnight) community noise exposure at children's home, estimated by means of a land use regression model using various predictors (roads, schools, greenness, residential and informal settlements). Outcomes were the Strengths and Difficulties Questionnaire (SDQ) and Regional Project on Child Development Indicators (PRIDI) at 3 years of age and the Child Behavior Checklist (CBCL) and International Development and Early Learning Assessment (IDELA) at 6 years of age. We investigated the relationship between noise exposure and development using cross-sectional and longitudinal regression models.

RESULTS

Data from 3385 children at 3 years of age and 1546 children at 6 years of age were analysed. Mean Lden and Lnight levels were 70.3 dB and 61.2 dB, respectively. In cross-sectional analyses a 10 dB increase of Lden above 70 dB was associated with a 32% increase in the odds of borderline or abnormal SDQ total difficulties score (OR = 1.32, 95% CI: 1.04; 1.68) and 0.72 standard deviation (SD) increase in the CBCL total problems z-score (95% CI: 0.55; 0.88). No cross-sectional association was found for cognitive development. In longitudinal analyses, each 10 dB increase was associated with a 0.52 SD increase in behavioral problems (95% CI: 0.28; 0.77) and a 0.27 SD decrease in cognition (95%-CI: 0.55; 0.00). Results for Lnight above 60 dB were similar.

DISCUSSION

Our findings suggest that community noise exposure above Lden of 70 dB and Lnight of 60 dB may impair behavioral and cognitive development of preschool children.

Strain Comparison in Rats Differentiates Strain-Specific from More General Correlates of Noise-Induced Hearing Loss and Tinnitus

Experiments in rodent animal models help to reveal the characteristics and underlying mechanisms of pathologies related to hearing loss such as tinnitus or hyperacusis. However, a reliable understanding is still lacking. Here, four different rat strains (Sprague Dawley, Wistar, Long Evans, and Lister Hooded) underwent comparative analysis of electrophysiological (auditory brainstem responses, ABRs) and behavioral measures after noise trauma induction to differentiate between strain-dependent trauma effects and more consistent changes across strains, such as frequency dependence or systematic temporal changes. Several hearing- and trauma-related characteristics were clearly strain-dependent. Lister Hooded rats had especially high hearing thresholds and were unable to detect a silent gap in continuous background noise but displayed the highest startle amplitudes. After noise exposure, ABR thresholds revealed a strain-dependent pattern of recovery. ABR waveforms varied in detail among rat strains, and the difference was most prominent at later peaks arising approximately 3.7 ms after stimulus onset. However, changes in ABR waveforms after trauma were small compared to consistent strain-dependent differences between individual waveform components. At the behavioral level, startle-based gap-prepulse inhibition (gap-PPI) was used to evaluate the occurrence and characteristics of tinnitus after noise exposure. A loss of gap-PPI was found in 33% of Wistar, 50% of Sprague Dawley, and 75% of Long Evans rats. Across strains, the most consistent characteristic was a frequency-specific pattern of the loss of gap-PPI, with the highest rates at approximately one octave above trauma. An additional range exhibiting loss of gap-PPI directly below trauma frequency was revealed in Sprague Dawley and Long Evans rats. Further research should focus on these frequency ranges when investigating the underlying mechanisms of tinnitus induction.

Stress hormone biosynthesis-based genes and lifestyle moderated the association of noise exposure with blood pressure in a cohort of Chinese tobacco factory workers: A cross-sectional analysis

When evaluating noise-related cardiovascular risk, noise is generally solely assessed as the major stressor. However, cardiovascular effect of other simultaneous exposure events, such as unhealthy lifestyle and genetic variation, is easily neglected. The aim of this study is to estimate the combined effect of noise and lifestyle on blood pressure alteration, particularly under different genetic background. This study included 536 workers from a tobacco factory in Wuhan, China, who were divided into high exposure group and low exposure group according to noise measurement in their working area. All participants took annual physical examination and questionnaire survey to provide information on individual systolic and diastolic blood pressure (SBP and DBP) and lifestyle (smoking, drinking and physical activity). Single nucleotide polymorphism at genes related to stress hormone production were determined. Moderated moderation models were constructed to investigate the interaction effect of noise exposure and lifestyle factors on blood pressure with regard to different genetic background. We identified an expected trend in association between noise exposure and SBP among active smokers (P = 0.086). The moderated moderation analysis showed significant three-way interaction effect (COMT rs4680 × smoking status × noise exposure levels) on SBP or DBP (both P < 0.05). For COMT rs4680 GA+AA genotype carriers, active smoking significantly moderated the association between noise exposure and SBP or DBP (both P < 0.05). The results indicated that for COMT rs4680 A allele carriers, tobacco and noise exposure contribute collectively to blood pressure alteration, supporting that stress hormone production may play a certain role in the smoke-and-noise-induced cardiovascular effect.

miR-153/KCNQ4 axis contributes to noise-induced hearing loss in a mouse model

Damage to the cochlear sensory epithelium is a key contributor to noise-induced sensorineural hearing loss (SNHL). KCNQ4 plays an important role in the cochlear potassium circulation and outer hair cells survival. As miR-153 can target and regulate KCNQ4, we sought to study the role of miR-153 in SNHL. 12-week-old male CBA/J mice were exposed to 2-20 kHz broadband noise at 96 dB SPL to induce temporary threshold shifts and 101 dB SPL to induce permanent threshold shifts. Hearing loss was determined by auditory brainstem responses (ABR). Relative expression of miR-153 and KCNQ4 in mice cochlea were determined by Real-Time quantitative PCR. miR-153 mimics were co-transfected with wild type or mutated KCNQ4 into HEK293 cells. Luciferase reporter assay was used to validate the binding between miR-153 and KCNQ4. AAV-sp-153 was constructed and administrated intra-peritoneally 24- and 2-h prior and immediately after noise exposure to knockdown miR-153. The KCNQ4 is mainly expressed in outer hair cells (OHCs). We showed that the expression of KCNQ4 in mice cochlea was reduced and miR-153 expression was significantly increased after noise exposure compared to control. miR-153 bound to 3'UTR of KNCQ4, and the knockdown of miR-153 with the AAV-sp-153 administration restored KCNQ4 mRNA and protein expression. In addition, the knockdown of miR-153 reduced ABR threshold shifts at 8, 16, and 32 kHz after permanent threshold shifts (PTS) noise exposure. Correspondingly, OHC losses were attenuated with inhibition of miR-153. This study demonstrates that miR-153 inhibition significantly restores KNCQ4 in cochlea after noise exposure, which attenuates SNHL. Our study provides a new potential therapeutic target in the prevention and treatment of SNHL.

A neurobiological link between transportation noise exposure and metabolic disease in humans

BACKGROUND

Chronic transportation noise exposure associates with cardiovascular events through a link involving heightened stress-associated neurobiological activity (as amygdalar metabolic activity, AmygA) on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT). Increased AmygA also associates with greater visceral adipose tissue (VAT) and type 2 diabetes mellitus (DM). While relationships between noise exposure and VAT and DM have been reported, the underlying mechanisms remain incompletely understood. We tested whether: (1) transportation noise exposure associates with greater (a) baseline and gains in VAT and (b) DM risk, and (2) heightened AmygA partially mediates the link between noise exposure and these metabolic diseases.

METHODS

VAT was measured in a retrospective cohort (N = 403) who underwent clinical ¹⁸F-FDG-PET/CT. AmygA was measured in those with brain imaging (N = 238). Follow-up VAT was remeasured on available imaging (N = 67). Among individuals (N = 224) without baseline DM, incident DM was adjudicated over 2 years from clinical records. Noise (24-h average) was modeled at each individual's home address. Linear regression, survival, and mediation analyses were employed.

RESULTS

Higher noise exposure (upper tertile vs. others) associated with greater: baseline VAT (standardized β [95% confidence interval (CI)]= 0.230 [0.021, 0.438], p = 0.031), gains in VAT (0.686 [0.185, 1.187], p = 0.008 adjusted for baseline VAT), and DM (hazard ratio [95% CI]=2.429 [1.031, 5.719], p = 0.042). The paths of: ↑noise exposure→↑AmygA→↑baseline VAT and ↑noise exposure→↑AmygA→↑subsequent DM were significant (p < 0.05).

CONCLUSIONS

Increased transportation noise exposure associates with greater VAT and DM. This relationship is partially mediated by stress-associated neurobiological activity. These findings suggest altered neurobiology contributes to noise exposure's link to metabolic diseases.

Land use regression modelling of community noise in São Paulo, Brazil

Noise pollution has negative health consequences, which becomes increasingly relevant with rapid urbanization. In low- and middle-income countries research on health effects of noise is hampered by scarce exposure data and noise maps. In this study, we developed land use regression (LUR) models to assess spatial variability of community noise in the Western Region of São Paulo, Brazil.We measured outdoor noise levels continuously at 42 homes once or twice for one week in the summer and the winter season. These measurements were integrated with various geographic information system variables to develop LUR models for predicting average A-weighted (dB(A)) day-evening-night equivalent sound levels (L_den) and night sound levels (L_night). A supervised mixed linear regression analysis was conducted to test potential noise predictors for various buffer sizes and distances between home and noise source. Noise exposure levels in the study area were high with a site average L_den of 69.3 dB(A) ranging from 60.3 to 82.3 dB(A), and a site average L_night of 59.9 dB(A) ranging from 50.7 to 76.6 dB(A). LUR models had a good fit with a R² of 0.56 for L_den and 0.63 for L_night in a leave-one-site-out cross validation. Main predictors of noise were the inverse distance to medium roads, count of educational facilities within a 400 m buffer, mean Normalized Difference Vegetation Index (NDVI) within a 100 m buffer, residential areas within a 50 m (L_den) or 25 m (L_night) buffer and slum areas within a 400 m buffer. Our study suggests that LUR modelling with geographic predictor data is a promising and efficient approach for noise exposure assessment in low- and middle-income countries, where noise maps are not available.

The influence of developmental noise exposure on the temporal processing of acoustical signals in the auditory cortex of rats

Previous experiments have acknowledged that inappropriate or missing auditory inputs during the critical period of development cause permanent changes of the structure and function of the auditory system (Bures et al., 2017). We explore in this study how developmental noise exposure influences the coding of temporally structured stimuli in the neurons of the primary auditory cortex (AC) in Long Evans rats. The animals were exposed on postnatal day 14 (P14) for 12 minutes to a loud (125 dB SPL) broad-band noise. The responses to an amplitude-modulated (AM) noise, frequency-modulated (FM) tones, and click trains, were recorded from the right AC of rats of two age groups: young-adult (ca. 6 months old) and adult (ca. 2 years old), both in the exposed animals and in control unexposed rats. The neonatal exposure resulted in a higher synchronization ability (phase-locking) of the AC neurons for all three stimuli; furthermore, the similarity of neuronal response patterns to repetitive stimulation was higher in the exposed rats. On the other hand, the exposed animals showed a steeper decline of modulation-transfer functions towards higher modulation frequencies/repetition rates. Differences between the two age groups were also apparent; in general, aging had qualitatively the same effect as the developmental exposure. The current results demonstrate that brief noise exposure during the maturation of the auditory system influences both the temporal and the rate coding of periodically modulated sounds in the AC of rats; the changes are permanent and observable up to late adulthood.

Low-sound-level auditory processing in noise-exposed adults

Early signs of noise-induced hearing damage are difficult to identify, as they are often confounded by factors such as age, audiometric thresholds, or even music experience. Much previous research has focused on deficits observed at high intensity levels. In contrast, the present study was designed to test the hypothesis that noise exposure causes a degradation in low-sound-level auditory processing in humans, as a consequence of dysfunction of the inner hair cell pathway. Frequency difference limens (FDLs) and amplitude modulation depth discrimination (MDD) were measured for five center frequencies (0.75, 1, 3, 4 and 6 kHz) at 15 and 25 dB sensation level (SL), as a function of noise exposure, age, audiometric hearing loss, and music experience. Forty participants, aged 33-75 years, with normal hearing up to 1 kHz and mild-to-moderate hearing loss above 2 kHz, were tested. Participants had varying degrees of self-reported noise exposure, and varied in music experience. FDL worsened as a function of age. Participants with music experience outperformed the non-experienced in both the FDL and MDD tasks. MDD thresholds were significantly better for high-noise-exposed, than for low-noise-exposed, participants at 25 dB SL, particularly at 6 kHz. No effects of age or hearing loss were observed in the MDD. It is possible that the association between MDD thresholds and noise exposure was not causal, but instead was mediated by other factors that were not measured in the study. The association is consistent, qualitatively, with a hypothesized loss of compression due to outer hair cell dysfunction.

Hazardous sound outputs of white noise devices intended for infants

OBJECTIVES

To measure the sound intensity of popular infant white noise machines and Apple iPhone applications (apps) as they vary with volume setting and distance, and compare these output levels with current National Institute for Occupational Safety and Health (NIOSH) noise exposure threshold recommendations.

METHODS

A total of eight infant white noise machines and six iPhone applications were included in the study based on product rating, number of ratings, and cost. The NIOSH Sound Level Meter application through the Apple App Store was used to measure output levels in A-weighted decibels (dBA). Each device was tested at its lowest and highest volume setting and at speaker-to-microphone distances simulating placement within a crib (10 cm), just outside of a crib rail (30 cm), and on a nightstand across the room (100 cm).

RESULTS

At the minimum volume setting, no device exceeded the NIOSH recommended noise exposure threshold of 85 dBA at any distance tested. At maximum volume setting, nine out of fourteen (64.3%) devices exceeded output levels of 85 dBA at a speaker-to-microphone distance of 10 cm. No device exceeded the recommended threshold at its maximal volume when placed 30 cm or 100 cm away.

CONCLUSION

Excessive white noise exposure has the potential to lead to noise-induced hearing loss and other adverse health effects in the neonatal and infant population. We recommend conservative use of white noise machines and apps by avoiding maximal volume setting and placing any device well outside of the crib or at least 30 cm away from the child. To promote safe use of white noise devices, future studies are needed to fully understand the association between early noise exposure and hearing loss in infants.

A community noise survey in Southwest Detroit and the value of supplemental metrics for truck noise

Noise exposure can affect sleep, health and cognitive performance, and it disproportionately affects communities of color. This study has the objective of evaluating both conventional and supplemental noise metrics in a community noise survey examining Southwest Detroit, Michigan, a densely populated and industrialized area with extensive truck traffic on residential streets. Sound pressure level (SPL) monitors were deployed at 21 residential sites within 900 m of a major interstate highway. With assistance from youth volunteers, continuous SPL measurements were obtained for 1.5-7 days at each site, and short-term vehicle counts on local roads were recorded. We calculated conventional noise metrics, including the day-evening-night average sound level L_DEN and the 90th percentile 1-hr maximum L₁₀(h), and evaluated the effect of distance from highways, traffic volume, time-of-day, and other factors. Supplemental metrics potentially appropriate for intermittent traffic noise were calculated, including fraction of time over specific SPL thresholds using a new metric called F_DEN, which is the fraction of time over 60, 65 and 70 dB during night, evening and daytime periods, respectively, and a peak noise metric called L_2P(h), which utilizes the 98th percentile SPL within time blocks to increase robustness. The conventional metrics indicated five sites that exceeded 70 dB, and the highest noise levels were found within ~50 m of truck routes, arterials and freeway ramps. The estimated impact of truck traffic ranged up to 17 dB for hourly averages and to 33 dB for 1-s peaks. The conventional metrics did not always capture short-term noise exposures, which may be especially important to annoyance and sleep issues. In addition to showing widespread exposure to traffic noise in the study community that warrants consideration of noise abatement strategies, the study demonstrates the benefits of supplemental noise metrics and community engagement in noise assessment.

Correlations between cochlear pathophysiology and behavioral measures of temporal and spatial processing in noise exposed macaques

Noise-induced hearing loss (NIHL) is known to have significant consequences for temporal, spectral, and spatial resolution. However, much remains to be discovered about their underlying pathophysiology. This report extends the recent development of a nonhuman primate model of NIHL to explore its consequences for hearing in noisy environments, and its correlations with the underlying cochlear pathology. Ten macaques (seven with normal-hearing, three with NIHL) were used in studies of masked tone detection in which the temporal or spatial properties of the masker were varied to assess metrics of temporal and spatial processing. Normal-hearing (NH) macaques showed lower tone detection thresholds for sinusoidally amplitude modulated (SAM) broadband noise maskers relative to unmodulated maskers (modulation masking release, MMR). Tone detection thresholds were lowest at low noise modulation frequencies, and increased as modulation frequency increased, until they matched threshold in unmodulated noise. NH macaques also showed lower tone detection thresholds for spatially separated tone and noise relative to co-localized tone and noise (spatial release from masking, SRM). Noise exposure caused permanent threshold shifts that were verified behaviorally and audiologically. In hearing-impaired (HI) macaques, MMR was reduced at tone frequencies above that of the noise exposure. HI macaques also showed degraded SRM, with no SRM observed across all tested tone frequencies. Deficits in MMR correlated with audiometric threshold changes, outer hair cell loss, and synapse loss, while the differences in SRM did not correlate with audiometric changes, or any measure of cochlear pathophysiology. This difference in anatomical-behavioral correlations suggests that while many behavioral deficits may arise from cochlear pathology, only some are predictable from the frequency place of damage in the cochlea.

Tinnitus characteristics at high-and low-risk occupations from occupational noise exposure standpoint

INTRODUCTION

The aim of the present study was to compare tinnitus characteristics in high- and low-risk occupations from the occupational noise exposure standpoint, considering demographic data, hearing loss and concomitant diseases.

METHODS

Demographic data, characteristics of tinnitus, hearing and concomitant diseases were recorded in the questionnaires. Their pure tone air conduction thresholds were determined using a double-channel diagnostic Audiometer and the Bone Conduction was assessed using a B-71 bone vibrator.

RESULTS

Totally, 6.3% subjects (6.8% high-risk group and 5.6% low-risk group) had subjective tinnitus, mainly as whistling sound. In the high-risk group, tinnitus was mainly left-sided (41.18%) and hearing loss was mild. Bilateral tinnitus (52.63%) and slight hearing loss were observed predominantly in the low-risk group.

CONCLUSIONS

The study showed higher incidence of tinnitus in high-risk professions regarding with occupational noise exposure.

Impact of a visual indicator on the noise level in an emergency medical dispatch centre - a pilot study

BACKGROUND

Noise levels are monitored in call centres. A maximum of 52 to 55 dB(A) is recommended in order to prevent adverse events. We aimed at assessing the noise level and the impact of a visual noise indicator on the ambient noise level in a French Regional Emergency Medical Dispatch Centre (EMDC).

METHODS

We conducted an observational study in the EMDC of the SAMU25 (University Hospital of Besancon). We measured the noise level using a SoundEarII® noise indicator (Dräger Medical SAS, France). The measurement took place in two phases on three consecutive days from 00:00 to 11:59 PM. At baseline, phase 1, the device recorded the average ambient noise for each minute without visual indication. Secondly, phase 2 included a sensor mounted with a light that would turn on green if noise was below 65 dB(A), orange if noise ever exceeded 65 and red if it exceeded 75 dB(A).

RESULTS

In the presence of the visual noise indicator, the L_Aeq was significantly lower than in the absence of visual noise indicator (a mean difference of - 4.19 dB; P < 10^-3). It was higher than 55 dB(A) in 84.9 and 43.9% of the time in phases 1 and 2, respectively.

CONCLUSIONS

The noise levels were frequently higher than the standards, and sometimes close to recommended limits, requiring preventive measures. The noise indicator had a positive effect on the ambient noise level. This work will allow the implementation of effective prevention solutions and, based on future assessments, could improve operators' well-being and better care for patient.

Age-related and noise-induced hearing loss alters grasshopper mouse (Onychomys) vocalizations

Age-related and noise-induced hearing loss disorders are among the most common pathologies affecting Americans across their lifespans. Loss of auditory feedback due to hearing disorders is correlated with changes in voice and speech-motor control in humans. Although rodents are increasingly used to model human age- and noise-induced hearing loss, few studies have assessed vocal changes after acoustic trauma. Northern grasshopper mice (Onychomys leucogaster) represent a candidate model because their hearing sensitivity is matched to the frequencies of long-distance vocalizations that are produced using vocal fold vibrations similar to human speech. In this study, we quantified changes in auditory brainstem responses (ABRs) and vocalizations related to aging and noise-induced acoustic trauma. Mice showed a progressive decrease in hearing sensitivity across 4-32 kHz, with males losing hearing more rapidly than females. In addition, noise-exposed mice had a 61.55 dB SPL decrease in ABR sensitivity following a noise exposure, with some individuals exhibiting a 21.25 dB recovery 300-330 days after noise exposure. We also found that older grasshopper mice produced calls with lower fundamental frequency. Sex differences were measured in duration of calls with females producing longer calls with age. Our findings indicate that grasshopper mice experience age- and noise- induced hearing loss and concomitant changes in vocal output, making them a promising model for hearing and communication disorders.

Long-term exposure to traffic noise and mortality: A systematic review and meta-analysis of epidemiological evidence between 2000 and 2020

We aimed to update the evidence-base of long-term noise exposures from road, rail, and aircraft traffic on both non-accidental and cardiovascular mortality. A systematic review and meta-analysis were conducted following PRISMA guidelines. The literature was searched using PubMed, Scopus, Web of Science, and EMBASE for the period between January 01, 2000 and October 05, 2020. 13 studies were selected for final review. The risk of bias and overall quality of evidence was evaluated using a pre-defined list of criteria. Risk estimates from each study were converted into per 10 dB higher of L_den for each traffic source. Inverse-Variance heterogeneity (I-Vhet) meta-analysis was used to pool these individual risk estimates, along with assessment of heterogeneity and publication bias. Sensitivity analyses include using random-effect model and leave-one-out meta-analysis. Subgroup analyses by study design and noise exposure assessment were conducted to explore potential sources of heterogeneity. For road traffic, the pooled relative risk (RR) per 10 dB higher L_den for mortality from non-accidental causes was 1.01 (95% CI: 0.98, 1.05) (5 studies, I² = 78%), CVD was 1.01 (95% CI: 0.98, 1.05) (5 studies, I² = 41%), ischemic heart disease (IHD) was 1.03 (95% CI: 0.99, 1.08) (7 studies, I² = 46%), and stroke was 1.05 (95% CI: 0.97, 1.14) (5 studies, I² = 62%). The overall quality of evidence for most meta-analyses was rated as very low to low, except for CVD or IHD mortality, for which the quality of evidence was rated as moderate. A possible threshold of 53 dB was visually suggested for CVD-related mortality from road traffic noise in the trend analysis. For aircraft noise, pooled estimates were based on fewer studies and varied by mortality outcomes. Evidence of long-term exposure to traffic noise on mortality remains weak except the association between road traffic noise and IHD mortality. High-quality longitudinal studies are required to better characterise mortality effects of traffic noise.

Noise exposure assessment of occupational health and safety (OHS) consultants: A preliminary study

No published noise exposure assessment of occupational health and safety (OHS) consultants exists. An assessment was performed to quantify the noise level of OHS consultants while they were on site at a client's facility. OHS consultants wore a dosimeter set to A-weighting, slow response, 60 s log interval and a criterion level of 85dBA with a 3 dB exchange rate. Both the projected time-weighted average (TWA) and projected dose were recorded. Of the 32 noise assessments collected, three had projected TWAs that exceeded the occupational exposure limit of 85 dBA. Nearly 75% of the projected TWA measurements were equal or greater than the Action Level of 80 dBA. According to best practices, occupational noise levels greater than 80 dBA present a risk for noise-induced hearing loss and, therefore, a hearing loss prevention program should be implemented.

Changes in audiometric threshold and frequency selectivity correlate with cochlear histopathology in macaque monkeys with permanent noise-induced hearing loss

Exposure to loud noise causes damage to the inner ear, including but not limited to outer and inner hair cells (OHCs and IHCs) and IHC ribbon synapses. This cochlear damage impairs auditory processing and increases audiometric thresholds (noise-induced hearing loss, NIHL). However, the exact relationship between the perceptual consequences of NIHL and its underlying cochlear pathology are poorly understood. This study used a nonhuman primate model of NIHL to relate changes in frequency selectivity and audiometric thresholds to indices of cochlear histopathology. Three macaques (one Macaca mulatta and two Macaca radiata) were trained to detect tones in quiet and in noises that were spectrally notched around the tone frequency. Audiograms were derived from tone thresholds in quiet; perceptual auditory filters were derived from tone thresholds in notched-noise maskers using the rounded-exponential fit. Data were obtained before and after a four-hour exposure to a 50-Hz noise centered at 2 kHz at 141 or 146 dB SPL. Noise exposure caused permanent audiometric threshold shifts and broadening of auditory filters at and above 2 kHz, with greater changes observed for the 146-dB-exposed monkeys. The normalized bandwidth of the perceptual auditory filters was strongly correlated with audiometric threshold at each tone frequency. While changes in audiometric threshold and perceptual auditory filter widths were primarily determined by the extent of OHC survival, additional variability was explained by including interactions among OHC, IHC, and ribbon synapse survival. This is the first study to provide within-subject comparisons of auditory filter bandwidths in an animal model of NIHL and correlate these NIHL-related perceptual changes with cochlear histopathology. These results expand the foundations for ongoing investigations of the neural correlates of NIHL-related perceptual changes.

Assessment of low-frequency noise from wind turbines under different weather conditions

BACKGROUND

Low-frequency (20-200 Hz) noise (LFN) from wind turbines has received much public attention due to potential health concerns. This work tries to estimate the sound power level of wind turbines (L _W,A (dB)) at 20-200 Hz, which are not provided by manufacturers but essential for estimating LFN exposure (L _Aeq) of nearby residents.

METHODS

L _W,A at 20-200 Hz at three wind farms, each with a different brand of wind turbine (Brands A, B and C, respectively) were estimated using propagation model ISO 9613-2 under different weather conditions (rain, wind speed and wind direction) and validated with LFN monitoring data. The feasibility of using validated L _W,A as inputs for ISO 9613-2 to simulate residents' exposure (L _Aeq) to LFN were assessed considering interferences from rain, wind speed and wind directions.

RESULTS

The average L _W,A at 20-200 Hz ranged between 93.2 and 100.4 dB, 97.8 and 107.2 dB, and 96.5 and 110.4 dB for turbines of Brands A, B, and C, respectively, operating under wind speeds from 2 to 12 m/s. The L _W,A at wind speed of 2-8 m/s increased on average by 1.4, 1.9 and 1.7 dB per 1 m/s increase for Brands A, B and C, respectively. The differences in modeled L_eq obtained through the input of L _W,A into the ISO 9613-2 model and the measured L _Aeq for the three studied wind farms all fall within 1.5 dB.

CONCLUSION

This study successfully determined and validated the L _W,A of wind turbines of three brands, and subsequent residents' LFN exposure (with 1.5 dB difference) at three wind farms. Accurately obtaining LFN exposure will serve as the basis for assessing LFN exposure-health relationship. As wind power widely use worldwide, health impact should be assessed based on validated LFN exposure assessment.

Association between noise exposure and diabetes: meta-analysis

Diabetes is one of the typical chronic diseases, and its incidence is related to many environmental factors. At present, there is no radical cure for diabetes, so the prevention of diabetes is particularly important. In order to effectively prevent the occurrence of diabetes, it is necessary to understand the conditions leading to the occurrence of diabetes. Current studies have shown that long-term exposure to noise will increase the risk of diabetes. Literature was retrieved from Pubmed and Web of Science. The relationship between noise exposure and diabetes published in the past 10 years was retrieved from the literature. Two researchers screened the literatures and extracted the data according to the inclusion and exclusion criteria. Endnote software was used to manage the literature, and NOS (Newcastle-Ottawa Scale) scale was used to evaluate the quality of the included literatures. Random effects meta-analysis was used to comprehensively evaluate the noise exposure of diabetic patients, and stata13.1 was used for data analysis. After adherence to strict inclusion and exclusion criteria, eight studies on the association between noise and diabetes were selected, including five cohort studies and three cross-sectional studies, with a total of 514,570 participants and 23,708 diabetics. The results showed that exposure to noise increased the risk of developing diabetes (OR = 1.08; 95% CI = 1.03 ~ 1.12). From the analysis of these selected articles, it can be seen that there is a positive correlation between noise and the occurrence of diabetes. As a result, it is necessary to strengthen routine blood tests for people who have been exposed to noise for a long time, especially those who have to be exposed to noise due to their occupations.