Association between noise-induced hearing loss in the petrochemical workers and co-exposure to toluene, ethylbenzene, xylene, and styrene: a cross-section survey in southern China

Abstract Exposure to noise and high concentrations of organic solvents such as toluene, ethylbenzene, xylene, and styrene (TEXS) can cause hearing loss. However, there is limited information on the association between noise-induced hearing loss and low-level TEXS exposure. In this study, we conducted a cross-sectional survey, measuring pure-tone audiometry of 1496 petrochemical workers exposed to noise in South China from Octo to Dece 2020. Individual cumulative noise exposure (CNE) levels and benzene, toluene, ethylbenzene, xylene, and styrene (BTEXS) exposure were assessed, and the average CNE was 93.27 ± 4.92 dB(A)·years. The concentrations of BTEXS were considered as low-level due to they were far below the occupational exposure limits. Participats exposed to BTEXS were 569, 524, 156, 452, and 172 respectively. After adjusting for covariates such as smoking status, drinking status, BMI, using ear protection and personal protective equipment, earphone/headphone type and volume, and duration of use, all logistic regression model analyses showed that CNE was consistently positively associated with hearing loss (HL) and high-frequency hearing loss (HFHL). Compared with participants in the lowest quartile of CNE, participants in the highest quartile showed an OR of 5.229 (95% CI: 3.179, 8.598) for HFHL. TEXS exposure was significantly positively associated with HL (OR 1.679, 95%CI 1.086, 2.597), SFHL (OR 2.440, 95%CI 1.255, 4.744) and HFHL (OR 1.475, 95% CI 1.077, 2.020) in the two-pollutant models. And more, no interaction between CNE and TEXS exposure and their effects on HL and HFHL was observed. In conclusion, in the case of noise exposure, low-level TEXS exposure can still impair hearing function, mainly manifested as speech-frequency hearing loss. Co-exposure to noise and TEXS would cause more severe damage on hearing function than exposure to noise or TEXS alone. Therefore, TEXS-exposure workers should be included in hearing protection programs.