Combined effects of xylene and noise exposure at realistic low levels on hearing impairment: a cross-sectional study in China

Objectives To investigate the combined effect of low-level xylene and noise exposure on hearing impairment in Chinese manufacturing workers and to provide evidence for occupational hearing protection strategies in China. Methods A cross-sectional survey was conducted among 899 workers (295 co-exposed, 604 noise-only) in Jiaxing City, China from 2023 to 2025. Workplace noise and xylene concentrations were monitored, and pure-tone audiometry was performed with age-gender correction. Binary logistic regression and stratified regression analysis were used to evaluate risk factors for high-frequency hearing loss (HFHL). Results The HFHL prevalence was 5.76% in the combined exposure group and 2.48% in the noise-only group ( P = 0.01). Logistic regression model shows that the combined exposure group had a 5.49-fold higher HFHL risk ( P < 0.01). Hypertension, longer exposure duration, higher noise intensity and higher xylene concentration were independent risk factors for HFHL. Stratified analyses confirmed a higher HFHL risk in the combined exposure group across subgroups of age < 40/ ≥ 40 years, male workers, and exposure duration 0–5/6–10 years. Conclusions Combined xylene and noise exposure exerts a significant synergistic ototoxic effect even when both exposures are within Chinese national occupational exposure limits.