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Effects of co-exposure to CS 2 and noise on hearing and balance in rats: continuous versus intermittent CS 2 exposures.

Authors :
Chalansonnet M
Carreres-Pons M
Venet T
Thomas A
Merlen L
Boucard S
Cosnier F
Nunge H
Bonfanti E
Llorens J
Campo P
Pouyatos B
Source :
Journal of occupational medicine and toxicology (London, England) [J Occup Med Toxicol] 2020 May 11; Vol. 15, pp. 9. Date of Electronic Publication: 2020 May 11 (Print Publication: 2020).
Publication Year :
2020

Abstract

Background: Carbon disulfide (CS <subscript>2</subscript> ) exacerbates the effect of noise on hearing, and disrupts the vestibular system. The goal of this study was to determine whether these effects are also observed with intermittent CS <subscript>2</subscript> exposure.<br />Methods: Rats were exposed for 4 weeks (5 days/week, 6 h/day) to a band noise at 106 dB SPL either alone or combined with continuous (63 ppm or 250 ppm) or intermittent (15 min/h or 2 × 15 min/h at 250 ppm) CS <subscript>2</subscript> . Hearing function was assessed by measuring distortion product otoacoustic emissions (DPOAEs); balance was monitored based on the vestibulo-ocular reflex (VOR). Functional measurements were performed before, at the end of exposure and 4 weeks later. Histological analyses of the inner ear were also performed following exposure and after the 4-week recovery period.<br />Results: The results obtained here confirmed that CS <subscript>2</subscript> exposure exerts two differential temporary effects on hearing: (1) it attenuates the noise-induced DPOAE decrease below 6 kHz probably through action on the middle ear reflex when exposure lasts 15 min per hour, and (2) continuous exposure to 250 ppm for 6 h extends the frequency range affected by noise up to 9.6 kHz (instead of 6 kHz with noise alone). With regard to balance, the VOR was reversibly disrupted at the two highest doses of CS <subscript>2</subscript> (2 × 15 min/h and continuous 250 ppm). No morphological alterations to the inner ear were observed.<br />Conclusion: These results reveal that short periods of CS <subscript>2</subscript> exposure can alter the sensitivity of the cochlea to noise at a dose equivalent to only 10 times the short-term occupational limit value, and intermittent exposure to CS <subscript>2</subscript> (2 × 15 min/h) can alter the function of the vestibular system.<br />Competing Interests: Competing interestsThe authors declare that they have no competing interests.<br /> (© The Author(s) 2020.)

Details

Language :
English
ISSN :
1745-6673
Volume :
15
Database :
MEDLINE
Journal :
Journal of occupational medicine and toxicology (London, England)
Publication Type :
Academic Journal
Accession number :
32426022
Full Text :
https://doi.org/10.1186/s12995-020-00260-5