Effects of Coexposure to Noise and Mixture of Organic Solvents on Hearing in Dockyard Workers

Abstract

Questionnaire and audiometric data of 701 dockyard workers (517 noise and organic solvent mixture-exposed and 184 noise-only-exposed) were referred to 205 control subjects not exposed to either noise or solvents. The odds ratio (OR) of hearing loss was significantly increased by approximately 3 times in the noise-only group and by almost 5 times in the noise and solvent group. A moderate effect of solvent ototoxicity, in addition to noise, was observed on hearing threshold at a frequency 8 kHz. ORs for hearing loss were 1.12 for each increment of 1 year of age, 1.07 for every decibel of lifetime noise exposure (dB-A), and 1.004 for each increment of the index of lifetime exposure to solvents. The results suggest an additive damaging effect of coexposure to noise and organic solvents to the auditory organ.

Exposure to Organic Solvent Mixture and Hearing Loss: Literature Overview

“…In the study by M. Śliwińska-Kowalska et al, multiple linear regression analysis revealed a correlation between exposure to solvent mixture (expressed as a lifetime exposure index) and hearing threshold at 8 kHz in dockyard workers [5]. The same authors have demonstrated a similar relationship for 4, 6 and 8 kHz, when the analysis concerned dockyard and paint & lacquer industry workers (high and moderate solvent exposure, respectively) [9].…”

“…The mean lifetime exposure (exposure level × duration of employment) to toluene ranged from 31-203 ppm, to xylene from 84 to 696 ppm, and exposure index from 10 to 67 [4,5]. The highest-level exposure was encountered in a dockyard [5], and the lowest levels were found in aviation and Fig. 1.…”

“…1) [2,4], the workers were exposed to high solvent concentra--tions and noise (as in dockyard workers for whom the mean lifetime exposure to xylene was 696 ppm, to toluene 203 ppm, and the mean exposure index was 6.3 ( Fig. 2) [5,9].…”

“…For toluene, the current exposure concentration in the air ranged from 0 to 70 ppm, for xylene it ranged from 0-417 ppm; and the current exposure index ranged from 0.5 to 23 [1][2][3]. The mean lifetime exposure (exposure level × duration of employment) to toluene ranged from 31-203 ppm, to xylene from 84 to 696 ppm, and exposure index from 10 to 67 [4,5]. The highest-level exposure was encountered in a dockyard [5], and the lowest levels were found in aviation and Fig.…”

“…Age, noise exposure, and employment duration were the variables included most frequently in the multivariate logistic regression models; in some studies, gender, alcohol consumption, hypertension, diabetes, smoking, noise trauma, and family history were also incorporated. As regards the risk assessment of hearing loss, a few studies evaluated this outcome at high frequency [1][2][3], some at all frequencies [4,5,9], and two at middle speech frequencies [7,8]. Eleven studies assessed the effect of solvent exposure on audiometric hearing threshold; five papers evaluated central effects on hearing (stapedial decay and contralateral stapedial reflex, interrupted and distorted speech, evoked cortical response, and cognitive response) [3,[13][14][15][16].…”