Chronic exposure to low frequency noise at moderate levels causes impaired balance in mice.

Haruka Tamura,Tastuya Kusudo,Machiko Iida,Masashi Kato,Ichiro Yajima,Nobutaka Ohgami,Noriko Fujii,Hitoshi Yamashita,Kyoko Ohgami,Hiroyuki Itabe,Georges Chapouthier

doi:10.1371/journal.pone.0039807

Abstract

We are routinely exposed to low frequency noise (LFN; below 0.5 kHz) at moderate levels of 60–70 dB sound pressure level (SPL) generated from various sources in occupational and daily environments. LFN has been reported to affect balance in humans. However, there is limited information about the influence of chronic exposure to LFN at moderate levels for balance. In this study, we investigated whether chronic exposure to LFN at a moderate level of 70 dB SPL affects the vestibule, which is one of the organs responsible for balance in mice. Wild-type ICR mice were exposed for 1 month to LFN (0.1 kHz) and high frequency noise (HFN; 16 kHz) at 70 dB SPL at a distance of approximately 10–20 cm. Behavior analyses including rotarod, beam-crossing and footprint analyses showed impairments of balance in LFN-exposed mice but not in non-exposed mice or HFN-exposed mice. Immunohistochemical analysis showed a decreased number of vestibular hair cells and increased levels of oxidative stress in LFN-exposed mice compared to those in non-exposed mice. Our results suggest that chronic exposure to LFN at moderate levels causes impaired balance involving morphological impairments of the vestibule with enhanced levels of oxidative stress. Thus, the results of this study indicate the importance of considering the risk of chronic exposure to LFN at a moderate level for imbalance.

Highlights

Exposure to noise generated in occupational and daily environments is one of the community hazards in our society [1,2]
There is very limited information about the etiology of imbalance caused by Low frequency noise (LFN) and the influence of a moderate level of LFN on balance since it is basically difficult to reveal the pathogenesis of impaired balance caused by LFN stress in humans
This study showed for the first time that chronic exposure to LFN at a moderate level causes imbalance involving morphological impairments in the vestibule in mice

Summary

Introduction

Exposure to noise generated in occupational and daily environments is one of the community hazards in our society [1,2]. Low frequency noise (LFN) is constantly generated from natural and artificial sources. The frequency range of LFN is usually defined as being below 100 Hz, while that of infrasound is usually below 20 Hz [3]. LFN is ubiquitously detected in our modern society and is generated from many occupational and daily sources including transportation systems, industrial devices, air movement devices (e.g., wind turbines, compressors, ventilation and air-conditioning units) and household appliances (e.g., washing machines, refrigerators and freezers). We are routinely exposed to LFN generated from various devices in the daily environment. Our measurements showed LFN at moderate levels of about 70 dB sound pressure level (SPL) generated from various ordinary devices (Table 1)

Methods

Results

Conclusion