Temporary and permanent level shifts in distortion product otoacoustic emissions following noise exposure in an animal model

Noise-induced hearing loss [NIHL] is one of the most common occupational illnesses. Most of the studies on NIHL were conducted at high noise levels that people are rarely exposed to but in industries. The function of the outer hair cells [OHCs] is impaired after exposure to industrial noise. Distortion product otoacoustic emissions [DPOAEs] are useful in examination of noise-induced level shifts. To assess the function of OHCs by DPOAE temporary and permanent level shifts [TLSdp and PLSdp] in rabbits exposed to white noise at realistic levels typically found in industrial settings over a broad range of frequencies. 12 albino rabbits were divided into two groups: the experimental group rabbits which were exposed to 95 dB SPL white noise at 500-8000 Hz for 8 hrs/day for 5 consecutive days, and the control group rabbits with no exposure to noise. The function of OHCs was examined by DPOAE level [Ldp] in different occasions. The study groups were compared for DPOAE temporary and permanent level shifts [TLSdp and PLSdp] to assess the effect of noise on OHCs function. Noise-induced DPOAE levels [Ldp] were decreased up to 20.65 dB [on day 8] and 18.93 dB [on day 11] at 5888.50 Hz [p=0.081]. TLSdp and PLSdp were significantly decreased up to 17.99 dB and 16.27 dB, respectively in the experimental group. The most and least Ldp were significantly different [p<0.05]; they occurred at 5888.50 and 588.00 Hz, respectively. There were significant differences between temporary and permanent threshold shift at various frequencies [p<0.05]. These differences were mainly related to 5888.50 Hz compared to other frequencies in each ear [p<0.05]. DPOAEs are an attractive tool for obtaining information about small temporary or permanent threshold shifts, even when the pure tone audiogram is normal

[ effect of age on hearing impairment of employees in a textile factory]

To assess the effect of age on hearing impairment of employees in a textile factory. This was a cross-sectional study. 385 male workers in a textile factory took part in the study. Data were collected using a questionnaire containing items on demographic status and hearing diseases. In addition, audiomentric tests were carried out and total hearing loss and total hearing impairment for any workers were calculated. 301 [78.2%] employees were over age 40. There was a significant relationship between age and various types of jobs [Chi [2]=7.33; P<0.001]. 345 [89.6%] of employees had hearing impairment [hearing loss higher than 25 decibles] and 40 [10.4%] were healthy. Also there was a statistically significant relationship between age and hearing loss [Chi[2]=4.43; P<0.001]. and hearing impairment [chi[2]=6.38; p=0.004]. The highest prevalence of presbyacusis was related to the age group of 40-44 years old [59.3%]. In general hearing impairment was found to be high in this population and it was associated with type of jobs and age

Concise exposure and damage indicators for predicting foreseeable effects of work-related upper limb disorders

Since work-related musculoskeletal disorders [WMSDS] have a high prevalence in different industries, in order to quantify the prevalence of WMSDS of the upper limbs in of exposed group and find a relationship between exposure indices and effect indicators, this research was carried out. A total of 404 male exposed and of 120 male non-exposed workers of Qaemshahre [northern Iran] weaving factory located in the north of Iran were studied. Regarding the quantification of exposure, use was made of the Occupational Repetitive Actions [OCRA]. Also the Concise Damage Index [CDI] was calculated for any job and then statistically significant relationships between CDI and OCRA exposure indices were surveyed. It was considered that there were significant associations between OCRA and an effect indicators [CDI] represented by the prevalence of all the WMSDS of the upper limbs [R[2]=0.85, P=0.001]. When a logarithmic conversion of the relative exposure [OCRA] and injury indices was carried out, a simple and multiple linear regression model resulted that seems to provide a satisfactory and truly predictive performance of the risk of WMSDS of the upper limbs based on the exposure index, length of time, lack of recovery periods, and etc