Reinvigorating engineered noise controls: a systems approach.

OBJECTIVES: Hearing loss is a major worldwide health issue affecting an estimated 1.5 billion people. Causes of hearing loss include genetics, chemicals, medications, lifestyle habits such as smoking, and noise. Noise is probably the largest contributing factor for hearing loss. Noise arises from the workplace, ambient environment, and leisure activities. The easiest noise sources to control are workplace and environmental. Workplace noise is unique in that the employer is responsible for the noise and the worker. Also, workers may be exposed to much higher levels of noise than they would accept elsewhere. Employers follow the traditional hierarchy of controls (substitution/engineering, administrative, personal protective equipment [PPE]). Substituting or engineering a lower noise level actually reduces the hazard present to the worker but demand more capital investment. Administrative and PPE controls can be effective, but enforcement and motivation are essential to reducing risk and there is still some hearing loss for a portion of the workers. The challenge is to estimate the costs more clearly for managers. A systems engineering approach can help visualize factors affecting hearing health. MATERIAL AND METHODS: In this study, a systems engineering causal loop diagram (CLD) was developed to aid in understanding factors and their interrelationships. The CLD was then modeled in VenSim. The model was informed from the authors' expertise in hearing health and exposure science. Also, a case study was used to test the model. The model can be used to inform decision-makers of holistic costs for noise control options, with potentially better hearing health outcomes for workers. RESULTS: The CLD and cost model demonstrated a 4.3 year payback period for the engineered noise control in the case study. CONCLUSIONS: Systems thinking using a CLD and cost model for occupational hearing health controls can aid organizational managers in applying resources to control risk. Int J Occup Med Environ Health. 2023;36(5):672-84.

[Do hearing threshold levels in workers of the furniture industry reflect their exposure to noise?]. / Czy progi sluchu u pracowników przemyslu meblarskiego wynikaja z ich narazenia na halas?

BACKGROUND: The aim of the study was to analyze the hearing status of employees of a furniture factory with respect to their exposure to noise and the presence of additional risk factors of noise-induced hearing loss (NIHL). MATERIAL AND METHODS: Noise measurements, questionnaire survey and assessment of hearing, using pure tone audiometry, were carried out in 50 male workers, aged 20-57 years, directly employed in the manufacture of furniture. The actual workers' hearing threshold levels (HTLs) were compared with the predictions calculated according to PN-ISO 1999:2000 based on age, gender and noise exposure. RESULTS: Workers under study were exposed to noise at daily noise exposure levels of 82.7-94.8 dB (mean: 90.9 dB) for a period of 3-14 years. In all subjects, mean HTL at 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz did not exceed 25 dB. Nevertheless, high frequency notches were found in 11% of audiograms. The actual workers' HTLs at 3000-6000 Hz were similar to those predicted using PN-ISO 1999:2000. There were statistical significant differences between HTLs in subgroups of people with higher (> 78 mm Hg) and lower (≤ 78 mm Hg) diastolic blood pressure, smokers and non-smokers, and those working with organic solvents. Hearing loss was more evident in subjects affected by the additional risk factors specified above. CONCLUSIONS: The results confirm the need to consider, in addition to noise, also some other NIHL risk factors, such as tobacco smoking, elevated blood pressure, and co-exposure to organic solvents when estimating the risk of NIHL and developing the hearing conservation programs for workers. Med Pr 2016;67(3):337-351.

Genetic variants of CDH23 associated with noise-induced hearing loss.

OBJECTIVES: Noise-induced hearing loss (NIHL) is a complex disease resulting from the interaction between external and intrinsic/genetic factors. Based on mice studies, one of the most interesting candidate gene for NIHL susceptibility is CDH23-encoding cadherin 23, a component of the stereocilia tip links. The aim of this study was to analyze selected CDH23 single nucleotide polymorphisms (SNPs) and to evaluate their interaction with environmental and individual factors in respect to susceptibility for NIHL in humans. METHODS: A study group consisted of 314 worst-hearing and 313 best-hearing subjects exposed to occupational noise, selected out of 3,860 workers database. Five SNPs in CDH23 were genotyped using real-time PCR. Subsequently, the main effect of genotype and its interaction with selected environmental and individual factors were evaluated. RESULTS: The significant results within the main effect of genotype were obtained for the SNP rs3752752, localized in exon 21. The effect was observed in particular in the subgroup of young subjects and in those exposed to impulse noise; CC genotype was more frequent among susceptible subjects, whereas genotype CT appeared more often among resistant to noise subjects. The effect of this polymorphism was not modified by none of environmental/individual factors except for blood pressure; however, the latter one should be further investigated. Smoking was shown as an independent factor determining NIHL development. CONCLUSION: The results of this study confirm that CDH23 genetic variant may modify the susceptibility to NIHL development in humans, as it was earlier proven in mice. Because the differences between the 2 study groups were not necessarily related to susceptibility to noise but they also were prone to age-related cochlear changes, these results should be interpreted with caution until replication in another population.

Self-assessment of hearing status and risk of noise-induced hearing loss in workers in a rolling stock plant.

Noise measurements and questionnaire inquiries were carried out for 124 workers of a rolling stock plant to develop a hearing conservation program. On the basis of that data, the risk of noise-induced hearing loss (NIHL) was evaluated. Additionally, the workers' hearing ability was assessed with the (modified) Amsterdam inventory for auditory disability and handicap, (m)AIADH. The workers had been exposed to noise at A-weighted daily noise exposure levels of 74-110 dB for 1-40 years. Almost one third of the workers complained of hearing impairment and the (m)AIADH results showed some hearing difficulties in over half of them. The estimated risk of hearing loss over 25 dB in the frequency range of 3-6 kHz was 41-50% when the standard method of predicting NIHL specified in Standard No. ISO 1999:1990 was used. This risk increased to 50-67% when noise impulsiveness, coexposure to organic solvents, elevated blood pressure and smoking were included in calculations.

[Sources of occupational exposure to ultrasonic noise]. / Zródla ekspozycji zawodowej na halas ultradzwiekowy--ocena wybranych urzadzen.

BACKGROUND: Ultrasonic noise is defined as broadband noise containing high audible and low ultrasonic frequencies (from 10 kHz to 40 kHz). According to the most advanced knowledge, this type of noise exerts adverse effects on the hearing organ and the vestibular system. The aim of the study was to evaluate exposure to ultrasonic noise in occupational settings and to identify its essential sources. MATERIALS AND METHODS: The measurements of ultrasonic noise emitted by selected so called low frequency ultrasonic technological devices as well as grinders, circular saws, planers and processes, such as plasma-arc welding and air-acetylene welding, and others, were performed. The study concerned 233 workplaces, where the operators were supposed to be exposed to ultrasonic noise. The measurements were made under typical conditions of work and with reference to Polish standard PN-ISO 9612:2004. RESULTS: The sound pressure levels in the 1/3-octave bands from 10 kHz to 25 kHz (sometimes up to 40 kHz) occurring at workplaces exceeded the admissible values for 8-h exposure (maximum admissible intensity (MAI) values for ultrasonic noise) in all investigated cases of ultrasonic lace sewing machines and cutters as well as in 75% of grinders, 59.5% of ultrasonic welders, 42.9% of ultrasonic washers, and 28.6% of saws and planers. Moreover, in the majority (83.3%) of ultrasonic lace sewing machines and in a large part (33.5%) of welders, the recorded sound levels exceeded the admissible values of maximum sound pressure levels (MAI) in 1/3-octave bands. CONCLUSIONS: Our results indicate that ultrasonic welders and lace sewing machines are the major sources of occupational exposure to ultrasonic noise.

[Developing the method for assessing non-occupational exposure to noise]. / Opracowanie metody oceny pozazawodowej ekspozycji na halas.

BACKGROUND: Noise prevailing in the non-occupational environment, such as that experienced in disco or rock concerts may be dangerous to the condition of the human hearing organ. The existing methods for assessing the risk of hearing loss (e.g., specified in ISO 1999:1990) fails to consider the contribution of non-occupational noise to the overall noise exposure. The fact that there is no generally accepted method for assessing the contribution of individual exposures to non-occupational noise to be used in epidemiological studies is one of the reasons that the effect of the quoted ISO procedure is limited. The aim of this study was to develop a method enabling quantitative assessment of the individual level of non-occupational noise exposure and estimation of the exposure uncertainty in large groups of people. MATERIAL AND METHODS: Based on the available literature data and our own results, we established a database on noise levels associated with typical circumstances prevailing in the general environment. A questionnaire was developed to enable collection of data essential for defining individual exposures to non-occupational noise. Using the questionnaire data, a procedure for assessing the level of non-occupational noise exposure was developed and its reliability was determined by assessing the repeatability of the results of two determinations performed every three weeks and comparing the calculated levels of the noise exposures with the true levels. RESULTS: The values of individual non-occupational noise exposure, referred to 8h (LEX, 8h) in the study group of people, using the proposed methods ranged between 69 dB and 80 dB. This method allows to assess individual non-occupational exposures to noise at 1-2 dB error relative to the measured levels. The uncertainty of the method is within 4 dB. CONCLUSIONS: The proposed method enables a reliable assessment of non-occupational exposure to non-occupational noise and may be successfully applied in epidemiological studies.

[Effects of individual features on the measurement of vibration perception thresholds: standard setting for healthy people]. / Ocena wplywu czynników osobniczych na pomiar progu czucia wibracji--wyznaczenie norm dla osób zdrowych.

The thresholds of vibration perception in healthy people may differ significantly depending on individual and constitutional features: age, weight, height, race and gender, and also on various addictions like smoking or alcohol abuse. These variables have not as yet been analyzed in setting Polish standards of vibration perception thresholds used for therapeutical and certification purposes. The aim of the study was to develop a model that could render it possible to assess the normative values of vibration perception, taking account of individual features. The study covered 187 healthy persons free from exposure to vibration. Two methods were used to determine vibration perception thresholds: the standard Polish method and the method based on the ISO 13091-1/2001 standard. The methods differed in the technical parameters (contact force of vibrating probe 1.2 N and 0.1; probe diameter 12 and 5 mm-standard method and the method according to ISO, respectively), the presentation of stimuli (ascending method versus von: Bekesy method) and their frequencies. Vibration perception thresholds were significantly influenced by age (within the range of 63-250 Hz-standard method; 4-250 Hz-method according to ISO), body mass (full range of frequencies--standard method; 4-125-method according to ISO) and height (single frequencies--both methods). A model for determining vibration perception thresholds, taking account of age, height and body mass of study subjects, was developed. The results of the study show that individual and constitutional features should be taken into consideration when interpreting the results of the vibration perception examinations conducted for the purpose of occupational disease certification.