2013-08-01 12:00 - Messages

Hearing Loss and Use of Hearing Protection Among Career Firefighters in the United States

Objective: To determine the prevalence and characteristics of noise-induced hearing loss (NIHL) and the use of hearing protection devices (HPDs) among career firefighters. Methods: A Web-based survey and a standard audiometric test were performed with 425 firefighters from three states in the United States. Results: More than 40% showed hearing loss in the noise-sensitive frequencies (4 and 6 kHz). The left ear showed significantly poorer hearing than the right ear. Firefighters having longer years of work in fire services demonstrated significantly worse hearing. Reported use of HPDs was 34% of the time that was needed. Firefighters who used HPDs less were significantly more likely to have hearing loss. Conclusions: This study demonstrated a considerable NIHL problem and low use of HPDs in firefighters. More comprehensive hearing conservation programs should be implemented to reduce NIHL for firefighters.

Source : Hong, OiSaeng RN, FAAN; Chin, Dal Lae RN, ; Samo, Daniel G., Journal of Occupational & Environmental Medicine, August 2013, vol. 55, no 8, p 960–965. http://dx.doi.org/10.1097/JOM.0b013e318293aee0

Assessment of subjective and objective measurement systems of earplug attenuation on an individual - RR975

Systems that measure earplug attenuation for individual wearers are commercially available and the work detailed in this report aimed to assess the performance and test the reliability of two types of available system: objective measurement and subjective equal loudness. Systems were chosen to represent a type of system rather than a specific model of device and because they: were commercially available through leading manufacturers; were designed for use by operators with a minimal level of training or expertise; could be used with a range of earplugs; and were typical of the state of the art. Both systems investigated were found to have benefits and limitations. A number of recommendations are presented

Source : http://www.hse.gov.uk/research/rrpdf/rr975.pdf

Coupling forces exerted on chain saws by inexperienced tree fellers

Prolonged, intensive exposure to vibrations produced by vibrating tools could cause non-specific disorders in upper extremities of the operator, referred to as hand-arm vibration syndrome (HAVS). The severity of HAVS is affected by the magnitude of coupling forces exerted on the tool handle. The aim of the study was to measure the coupling forces exerted by inexperienced tree fellers on chain saws. Forces exerted by inexperienced tree fellers were compared to those of professional lumberjacks to investigate the relationship between the coupling forces and the experience of the chain saw operator. Coupling forces exerted on chain saws by inexperienced workers, using right and left hands, were measured in a group of 19 students. All measurements were done in forest environment. Coupling forces registered among trainees were about 5 N higher than forces exerted by professional lumberjacks. Our findings suggest that experienced workers use smaller forces than trainees.

Source : Jolanta Malinowska-Borowska, Grzegorz Zielinski, Coupling forces exerted on chain saws by inexperienced tree fellers, International Journal of Industrial Ergonomics, Volume 43, Issue 4, July 2013, Pages 283-287, ISSN 0169-8141, http://dx.doi.org/10.1016/j.ergon.2013.04.006.

Comparative analysis of exposure limit values of vibrating hand-held tools

In the European Union, one of every four workers claims to be exposed to vibration for up to 2 h of his/her working day. The use of vibrating hand-held tools is the most common cause of vibration-related injury in workers. Of all sectors of professional activity, the construction industry has the highest number of workers affected by vibration. European Directive 2002/44/EC on the minimum health and safety requirements regarding worker exposure to risks from physical agents (e.g. vibration) limits exposure to vibration. This study analysed the exposure level of construction workers to hand-arm vibration. For this research, vibration levels of the most common construction tools were compared, and the maximum time that each tool could be safely used was established. Finally, these limit values were compared to the tool vibration data provided by manufacturers. The results showed that for 42% of the tools studied, the daily exposure limit value was exceeded.

Source : Mónica López-Alonso, Rosalía Pacheco-Torres, Ma Dolores Martínez-Aires, Javier Ordoñez-García, Comparative analysis of exposure limit values of vibrating hand-held tools, International Journal of Industrial Ergonomics, Vol. 43, no 3, May 2013, p. 218-224. http://dx.doi.org/10.1016/j.ergon.2013.01.006

Whole body vibration exposures in bus drivers: A comparison between a high-floor coach and a low-floor city bus

Low back pain (LBP) is common in occupational bus drivers and studies have shown a dose–response relationship between whole body vibration (WBV) exposure and LBP. Bus design may be an important factor in determining the WBV exposure a bus driver receives. The purpose of this study was to determine whether differences exist in WBV exposures between two buses commonly used in long urban commuter routes: a high-floor coach and a low-floor city bus. Each bus was driven over a standardized test route which included four road types: a newer smooth freeway, a rougher old freeway, a city street segment, and a road segment containing several speed humps. WBV exposures were calculated per ISO 2631-1 (1997) and ISO 2631-5 (2004) standards. WBV exposures were significantly higher in the high-floor coach bus on the road segment containing speed humps. There were primarily small differences between buses in WBV exposures encountered on the city street and freeway segments. With respect to the ISO 2631-1 and European Union's A(8) and VDV(8) action limit values, both buses could be operated on the smooth freeway without exceeding the 8-hour action limits but would have to be operated less than 8 h when operating on the other road types. On average, the seats only attenuated 10% of the floor transmitted vibration and amplified the vibration exposures on the speed humps. Due to the low vibration attenuation performance of the bus driver's seat, evaluating different types of seats and seat suspensions may be merited.

Source : Ornwipa Thamsuwan, Ryan P. Blood, Randal P. Ching, Linda Boyle, Peter W. Johnson, Whole body vibration exposures in bus drivers: A comparison between a high-floor coach and a low-floor city bus, International Journal of Industrial Ergonomics, Volume 43, Issue 1, January 2013, Pages 9-17, ISSN 0169-8141, http://dx.doi.org/10.1016/j.ergon.2012.10.003.

The Importance of Properly Fitting Hearing Protection

Hearing loss is the No. 1 sensory disability in the world, and the World Health Organization estimates that 16 percent of hearing loss worldwide is attributable to occupational noise exposure. To minimize the risk of incurring hearing loss due to noise, it is important for organizations, employers and individuals to understand how they can better protect themselves and their employees from excessive noise in the workplace.

Source : http://ehstoday.com/hearing-protection/importance-properly-fitting-hearing-protection

A Job-Exposure Matrix for Occupational Noise: Development and Validation

Objective: To develop a job-exposure matrix (JEM) for occupational noise in Sweden and to estimate its validity. Methods: The JEM, developed by a group of experienced occupational hygienists, contains 321 job families with information regarding occupational noise from 1970 to 2004. The occupational noise information derives from measurements collected from different sources. The time period label has a 5-year scale starting in 1970. The estimated average 8h (TWA) noise level in decibel [dB(A)] for every 5-year period was coded either as <75 dB(A), 75–84 dB(A), or ≥85 dB(A) and the risk of peak level exposure assessed. The validity of the JEM is tested, using Svensson’s non-parametric methods based on classification consensus, reached by a second group of occupational hygienists. Results/Discussion: Validation results show ~ 80% agreement and no systematic differences, in classification, between the two different groups of occupational hygienists, classifying the occupational noise exposure. However, classification of peak level exposure did show a systematic difference in relative position. The results will give more power to the JEM that it gives a good general estimate for the occupational noise levels in Sweden for different job families during 1970–2004. We, thus, intend to use it in further studies and also make it available to collaborators

Source : Mattias Sjöström, Marie Lewné, Magnus Alderling, Pernilla Willix, Peter Berg, Per Gustavsson, and Magnus Svartengren. Ann Occup Hyg, 2013, vol. 57, no 6, p. 774-783, http://dx.doi.org/10.1093/annhyg/met001

Nodal control of grass trimmer handle vibration

Imposing node technique is applied to the grass trimmer shaft in order to achieve very low vibration (node) at the handle location. The optimum tuning frequencies of the two tuned vibration absorbers (TVAs) attached at 0.74L and 0.85L along the shaft of the grass trimmer are determined using the imposing node technique. Transverse deflection, experimental modal analysis and operating deflection shape analysis of the grass trimmer were carried out, and the results indicated that nearly zero deflection (node) was induced at the position very close the loop handle location. Moreover, the vibration along the segment of the shaft (0.70L–0.94L) was also found to have relatively small amplitude. The TVAs were found to have best performance with 71% reduction on the frequency weighted rms acceleration at the loop handle and 72% for the rear handle. The results from the experimental modal analysis and operating deflection shape revealed that the presence of the two TVAs has successfully reduced the large deformations of the loop and rear handle where the node was shifted nearer to the handle location. The effects of TVAs were also evaluated during the field test involving grass trimming operation and subjective rating. The results indicated that average reduction of frequency-weighted rms acceleration was by 25%, 69%, 17%, 58% in X h-, Y h-, Z h- axes and vibration total value respectively during the cutting operation. From the field test, subjective rating of vibration perception consistently rate better for the controlled grass trimmer. Relevance to industry Large numbers of workers are employed to perform grass trimming job in maintenance of parks and areas with undergrowth. This paper presents the imposing node technique to control handle vibration to the lowest value.

Source : Ko Ying Hao , Zaidi Mohd Ripin. International Journal of Industrial Ergonomics, Volume 43, Issue 1, p. 18-30. http://dx.doi.org/10.1016/j.ergon.2012.10.007

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