Objective To observe the effect of different occupational noise exposure levels on high-frequency hearing loss in shipbuilding workers.
Methods A retrospective cohort study was carried out in a shipbuilding enterprise in Pudong, Shanghai, by which the hearing test data of noise-exposed workers from 2016 to 2020 were collected. The workers were divided into three groups according to their exposure level, namely the high exposure group ≥ 90.0 dB(A), the moderate exposure group 85.0-90.0 dB(A), and the low exposure group < 85.0 dB(A). A Cox proportional hazards regression model was used to analyze the influencing factors for high-frequency hearing loss.
Results Totally 1 240 workers were included in the cohort in 2016, while 105 workers were added and 85 were lost during the follow-up period until December 31, 2020; 1 260 noise-exposed workers completed one or more health examinations and hearing tests, and 154 subjects had high-frequency hearing loss with an incidence rate of 12.22%. The results of the Cox proportional hazards regression model showed that the risk of high-frequency hearing loss among workers in the middle and high exposure groups was higher than that in the low exposure group (P < 0.01), with RR (95% CI) values of 4.594 (2.874-7.345) and 5.355 (3.277-8.749), respectively. Compared with workers exposed for less than 5 years, those exposed for 15-24 years, longer than or equal to 25 years, had an increased risk of high-frequency hearing loss (P < 0.01), with RR (95% CI) values of 3.883 (1.397-10.794) and 4.317 (1.542-12.085), respectively. Compared with non-exposed workers, the workers with exposure to multiple occupational hazards increased the risk of high-frequency hearing loss (P < 0.01), with a RR (95% CI) of 2.057 (1.627-3.030).
Conclusions The incidence of high-frequency hearing loss was high among workers exposed to noise in shipbuilding enterprises. Enterprises should actively seek effective intervention measures to reduce noise exposure intensity and exposure time to protect workers' hearing health.