Objective: This study aimed to examine the associations between acute workplace injury risk, ambient noise exposure, and hearing acuity, adjusting for reported hearing protection use.
Methods: In a cohort of 9220 aluminum manufacturing workers studied over six years (33 300 person-years, 13 323 person-jobs), multivariate mixed effects models were used to estimate relative risk (RR) of all injuries as well as serious injuries by noise exposure category and hearing threshold level (HTL) adjusting for recognized and potential confounders.
Results: Compared to noise <82 dBA, higher exposure was associated with elevated risk in a monotonic and statistically significant exposure-response pattern for all injuries and serious injuries with higher risk estimates observed for serious injuries [82-84.99 dBA: RR 1.26, 95% confidence interval (95% CI) 0.96-1.64; 85-87.99 dBA: RR 1.39, 95% CI 1.05-1.85; ≥88 dBA: RR 2.29, 95% CI 1.52-3.47]. Hearing loss was associated with increased risk for all injuries, but was not a significant predictor of risk for the subset of more serious injuries. Compared to those without hearing loss, workers with HTL ≥25 dB had 21% increased all injury risk (RR 1.21, 95% CI 1.09-1.33) while those with HTL 10-24.99 dB had 6% increased risk (RR 1.06, 95% CI 1.00-1.13). Reported hearing protection type did not predict injury risk.
Conclusion: Noise exposure levels as low as 85 dBA may increase workplace injury risk. HTL was associated with increased risk for all, but not the subset of serious, injuries. Additional study is needed both to confirm the observed associations and explore causal pathways.