ABSTRACT
OBJECTIVE: Evaluating the correlation between otoacoustic emission levels, styrene exposure, and oxidative stress biomarkers concentration in styrene-exposed subjects, to investigate the role of oxidative stress in outer hair cell damage. DESIGN: Distortion product otoacoustic emissions were measured in the exposed workers and in a control group. Separation between the distortion and reflection otoacoustic components was performed by time-frequency-domain filtering. The urinary concentration of the DNA and RNA oxidation products, namely 8-oxo-7,8-dihydroguanine (oxoGua), 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxodGuo), and 8-oxo-7,8-dihydroguanosine (oxoGuo), were evaluated. STUDY SAMPLE: Nine subjects exposed to styrene in a fiberglass factory, eight control subjects. The two groups were statistically equivalent in mean age. RESULTS: Statistically significant differences were found in the distortion component levels between the exposed and the control group. High levels of the oxidative damage biomarkers were found in the workers exposed to high levels of styrene. Significant negative correlation was found between the otoacoustic emission distortion component levels and the concentration of the oxoGuo biomarker. CONCLUSIONS: Exposure-induced damage of the cochlear amplifier is shown in the mid-frequency range, confirming animal experiments, in which hair cells in the cochlear middle turn were damaged. Hearing damage is consistent with the outer hair cell apoptosis pathway associated with oxidative stress.
Subject(s)
Hair Cells, Auditory, Outer/drug effects , Hearing Loss, Noise-Induced/chemically induced , Noise, Occupational/adverse effects , Occupational Diseases/chemically induced , Occupational Exposure/adverse effects , Occupational Health , Otoacoustic Emissions, Spontaneous/drug effects , Oxidative Stress/drug effects , Styrene/adverse effects , 8-Hydroxy-2'-Deoxyguanosine , Acoustics , Adult , Apoptosis/drug effects , Biomarkers/urine , Case-Control Studies , DNA Damage , Deoxyguanosine/analogs & derivatives , Deoxyguanosine/urine , Female , Guanine/analogs & derivatives , Guanine/urine , Guanosine/analogs & derivatives , Guanosine/urine , Hair Cells, Auditory, Outer/metabolism , Hair Cells, Auditory, Outer/pathology , Hearing Loss, Noise-Induced/diagnosis , Hearing Loss, Noise-Induced/physiopathology , Hearing Tests , Humans , Male , Middle Aged , Occupational Diseases/diagnosis , Occupational Diseases/physiopathology , Risk FactorsABSTRACT
The ototoxic effect of the exposure to styrene is evaluated, also in the presence of simultaneous exposure to noise, using otoacoustic emissions as biomarkers of mild cochlear damage. Transient-evoked and distortion product otoacoustic emissions were recorded and analyzed in a sample of workers (15 subjects) exposed to styrene and noise in a fiberglass manufacturing facility and in a control group of 13 non-exposed subjects. Individual exposure monitoring of the airborne styrene concentrations was performed, as well as biological monitoring, based on the urinary concentration of two styrene metabolites, the Mandelic and Phenylglyoxylic acids. Noise exposure was evaluated using wearable phonometers, and hearing loss with pure tone audiometry. Due to their different job tasks, one group of workers was exposed to high noise and low styrene levels, another group to higher styrene levels, close to the limit of 20 ppm, and to low noise levels. A significant negative correlation was found between the otoacoustic emission levels and the concentration of the styrene urinary metabolites. Otoacoustic emissions, and particularly distortion products, were able to discriminate the exposed workers from the controls, providing also a rough estimate of the slope of the dose-response relation between otoacoustic levels and styrene exposure.
Subject(s)
Air Pollutants, Occupational/adverse effects , Cochlea/drug effects , Hearing Loss, Noise-Induced/etiology , Noise/adverse effects , Otoacoustic Emissions, Spontaneous/drug effects , Styrene/adverse effects , Adult , Air Pollutants, Occupational/urine , Audiometry, Pure-Tone , Biomarkers/urine , Biotransformation , Case-Control Studies , Chromatography, High Pressure Liquid , Cochlea/injuries , Cochlea/physiopathology , Dose-Response Relationship, Drug , Environmental Monitoring/methods , Female , Gas Chromatography-Mass Spectrometry , Hearing Loss, Noise-Induced/diagnosis , Hearing Loss, Noise-Induced/physiopathology , Humans , Job Description , Male , Middle Aged , Occupational Exposure/adverse effects , Occupational Health , Saliva/metabolism , Styrene/urine , Tandem Mass SpectrometryABSTRACT
The sound exposure of classic orchestra musicians is not well assessed in Italy even though the protectionistic law includes all the working environments, as stated in the European Directive 2003/10/EC relative to the protection of workers against noise-induced damage. Scientific data in the literature show that the musicians are exposed to high daily personal exposure levels. These levels can systematically exceed the 85 dB(A) in the case of percussionists. In this study, preliminary results are shown relative to an experimental campaign performed in a lyric National Theatre. The aim of the study was the assessment of the risk due to high sound level in the theatre musicians and their cochlear functionality. The noise levels were measured by using wearable phonometers and multichannel sound analyzers. The signals were recorded during the whole working time in the rehearsal hall and in the fossa. The cochlear functionality was monitored before and immediately after rehearsal in a sample of volunteers by means of otoacoustic emission tests. Both TEOAE and DPOAE were measured using the ILO292 portable system. The data show that OAE-based tests can effectively discriminate between different classes of exposure. A good correlation was found between the daily exposure level and the DPOAE level.
