Evaluation of the risk of noise-induced hearing loss and the significance of occupational noise exposure limit among Chinese industrial workers

This study evaluated the excess risk of noise-induced hearing loss (NIHL) and its association with noise kurtosis (β) among 3421 Chinese male industrial workers exposed to complex noise. The objectives were to: (1) quantify the excess risk of NIHL, (2) examine how kurtosis influences this risk, and (3) recommend occupational exposure limits (OELs) for complex noise. Hearing loss was defined using two metrics: pure-tone averages (PTAs) PTA1234-AI (articulation-index-weighted average at 1–4 kHz) and PTA346 (unweighted average at 3–6 kHz). Logistic regression modeled hearing loss probability based on age, exposure level, and exposure duration. To assess kurtosis-related effects, workers were stratified into three kurtosis-based subgroups. Results showed that complex noise exposures yielded significantly higher excess risk than steady-state noise, and excess risk increased with higher kurtosis. Early noise exposure primarily elevated PTA346-defined hearing loss, with PTA1234-AI-defined hearing loss becoming more prominent as cumulative exposure increased. Derivative analysis of excess risk curves suggests lowering the standard OEL of 85 dBA to 80 dBA for PTA1234-AI and 77 dBA for PTA346. For high-kurtosis exposures (β ≥ 70 for PTA1234-AI; β ≥ 25 for PTA346), an additional 2 dBA reduction is recommended. These findings support more protective OELs for industrial workers exposed to non-steady-state, high-kurtosis noise environments.