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PubMed2005

Prospective noise induced changes to hearing among construction industry apprentices.

AIMS: To characterise the development of noise induced damage to hearing. METHODS: Hearing and noise exposure were prospectively monitored among a cohort of newly enrolled construction industry apprentices and a comparison group of graduate students, using standard pure tone audiometry and distortion product otoacoustic emissions (DPOAEs). A total of 328 subjects (632 ears) were monitored annually an average of 3.4 times. In parallel to these measures, noise exposure and hearing protection device (HPD) use were extensively monitored during construction work tasks. Recreational/non-occupational exposures also were queried and monitored in subgroups of subjects. Trade specific mean exposure L(eq) levels, with and without accounting for the variable use of hearing protection in each trade, were calculated and used to group subjects by trade specific exposure level. Mixed effects models were used to estimate the change in hearing outcomes over time for each exposure group. RESULTS: Small but significant exposure related changes in DPOAEs over time were observed, especially at 4 kHz with stimulus levels (L1) between 50 and 75 dB, with less clear but similar patterns observed at 3 kHz. After controlling for covariates, the high exposure group had annual changes in 4 kHz emissions of about 0.5 dB per year. Pure tone audiometric thresholds displayed only slight trends towards increased threshold levels with increasing exposure groups. Some unexpected results were observed, including an apparent increase in DPOAEs among controls over time, and improvement in behavioural thresholds among controls at 6 kHz only. CONCLUSIONS: Results indicate that construction apprentices in their first three years of work, with average noise exposures under 90 dBA, have measurable losses of hearing function. Despite numerous challenges in using DPOAEs for hearing surveillance in an industrial setting, they appear somewhat more sensitive to these early changes than is evident with standard pure tone audiometry.

Adult↗
PubMed2005

Hearing loss among operating engineers in American construction industry.

OBJECTIVE: Occupational noise exposure and noise-induced hearing loss (NIHL) among construction workers has long been recognized as a problem in the United States, yet little is known about the prevalence of NIHL among American construction workers. The purpose of this study was to determine the prevalence and characteristics of hearing loss among operating engineers (OEs) who operate heavy construction machinery. METHOD: As a part of hearing protection intervention, an audiometric test was conducted for both ears at frequencies 0.5 through 8 kHz in the soundproof booth. Prior to the audiometric test, a paper-pencil pre-hearing test questionnaire was administered and an otoscopic examination was completed. Prevalence of hearing loss was determined based on hearing threshold levels (HTLs) in the worst ear with a low fence of 25 dB. RESULT: A total of 623 workers were included in the analysis and they were predominantly middle-aged Caucasian males (mean age = 43 years, Caucasian = 90%, male = 92%). Over 60% of OEs showed hearing loss in the noise-sensitive higher frequencies of 4 and 6 kHz. The rate of hearing loss was particularly higher among workers who reported longer years of working in the construction industry. Workers showed significantly poorer hearing in the left ear, and a typical characteristic of NIHL, a V-notch at 4 or 6 kHz, was not shown in this population. Thirty-eight percent reported ringing/buzzing in the ear and 62% indicated having problems in understanding what people say in loud noise. Average reported use of hearing protection devices (HPDs) was 48% of the time they were required to be used. Significant inverse relationship was found between higher frequency (4-6 kHz) hearing loss and use of HPDs (r =-0.134, p < 0.001). Workers using HPDs more had significantly better hearing than those who did not. CONCLUSION: The study demonstrated a significant NIHL problem and low use of HPDs in OEs. An effective hearing conservation program, including a periodic audiometric testing and hearing protection intervention, for this study population should be in place.

Adult↗
PubMed2002

Anthropometric analysis of mandibular asymmetry in infants with deformational posterior plagiocephaly.

PURPOSE: The incidence of deformational posterior plagiocephaly has increased dramatically since 1992. We tested the hypothesis that mandibular asymmetry, associated with this condition, is secondary to anterior displacement of the ipsilateral temporomandibular joint. The response to molding helmet therapy was also evaluated. PATIENTS AND METHODS: A caliper was used to measure mandibular dimensions in 27 infants (16 boys and 11 girls) with deformational posterior plagiocephaly; the mean age was 6.2 months (range, 3 to 12 months). Anthropometric measures included ramal height (condylion-gonion), body length (gonion-gnathion), and condylion-gnathion. Gonial angle was calculated from the law of cosines: C(2) = A(2) + B(2) - 2AB cos c. The position of the temporomandibular joint was accepted as corresponding to auricular position and measured from tragion to subnasal. Cranial asymmetry was measured, in the horizontal plane, from orbitale superius to the contralateral parieto-occipital point at the level of inion. Ten of 27 patients were remeasured 5 months after beginning helmet therapy to evaluate change in mandibular dimensions. RESULTS: Two thirds of infants (67%) had right-sided and one third (33%) had left-sided deformational posterior plagiocephaly. The mean auricular anterior displacement was 79.7 mm on the affected side and 83.4 mm on the unaffected side. The mean difference of 3.8 mm between the sides was statistically significant (P <.001). Transverse cranial dimension averaged 136.0 mm on the affected side and 146.8 mm on the unaffected side; this was also significant (P <.001). There was a significant positive correlation between auricular displacement and cranial asymmetry [R(23) =.59, P <.01). Auricular (temporomandibular joint) displacement also resulted in an apparent mandibular asymmetry with rotation of the jaw to the affected side. Mean mandibular measurements on the affected and unaffected sides were ramus height of 35.2 and 36.4 mm, body length of 59.0 and 60.3 mm, and gonial angle of 127.1 degrees and 126.8 degrees, respectively. Comparison of the affected with the unaffected sides, using a paired-samples t test, was not statistically significant. Improvement in cranial asymmetry occurred with helmet therapy, but there was no correction of auricular and temporomandibular joint position. CONCLUSIONS: This study supports the clinical observation that the mandibular asymmetry in deformational posterior plagiocephaly is secondary to rotation of the cranial base and anterior displacement of the temporomandibular joint (quantified by anterior auricular position) and not the result of primary mandibular deformity.

Anthropometry↗
PubMed1982

Effect of diving and diving hoods on the bacterial flora of the external ear canal and skin.

The bacterial flora of the external ear canals and posterior auricular skin surfaces were investigated in a group of 26 divers after 25 dry-suit dives in harbor water and 20 dry-suit dives in clear test tank test. A control group of 16 divers wore rubber hoods 19 times for a similar period (25 to 30 min) but did not dive. The protective effect of 2% acetic acid was tested by instilling it in the left ear of 14 divers and 8 nondivers. Staphylococcus epidermidis, Propionibacterium acnes, alpha-hemolytic streptococci, and enteric gram-negative rods were the predominant isolates from skin and ear samples. After the divers dove or after they wore hoods without going in the water, there was a substantial increase in the number of these organisms on the skin (46.9%) or in the external ears (43.8%) of the divers. However, an increase in the bacterial counts in the external ear canals occurred in only 13.6% of the individuals treated prophylactically with acetic acid drops. Although no gram-negative rods were recovered from the skin or external ear canals of divers in clear tank water, 23 strains were isolated after the dives in harbor water. Identical gram-negative isolates also were recovered from the harbor water. Gram-negative organisms also were recovered from three newly acquired skin lacerations, where they persisted for at least 24 h. Our data show the acquisition of gram-negative rods when dives were made in polluted water. The data also demonstrate the increase in bacterial counts that occurs when rubber diving rods are worn (in or out of water) and that this increase can be controlled by pretreatment of ears with acetic acid.

Acetates↗
PubMed1995

Most Comfortable Listening Level and Speech Attenuation by Hearing Protectors.

Hearing protectors attenuate both the background noise and the useful sounds embedded in noise such as the sounds of speech and warning signals. An effective hearing protector is one that attenuates background noise while leaving sufficient energy of speech and warning signals to reach the ear of the worker. At present, however, there are no established criteria for assessing effective change in speech-to-noise ratio caused by hearing protection devices (HPDs). One such criterion could be a change in most comfortable (listening) level (MCL) for speech caused by the presence of HPDs. In this study the HPD-related shift in MCL for speech presented in quiet was measured and compared with two measures of noise attenuation: Noise Reduction Rating (NRR) and high-medium-low (H-M-L). The results indicate that the MCL shift may be a sensitive measure of speech attenuation by HPDs, which together with the appropriate H-M-L may describe technical properties of HPDs.

hearing protection↗