Risk assessment of noise-induced hearing loss among workers in a ship maintenance enterprise in Guangdong Province

Background Noise hazards of ship maintenance companies are serious and the noise environment is complex and changeable. It is difficult to assess the risk of hearing loss caused by noise exposure of workers.

Objective This study is conducted to assess the risk of hearing loss caused by noise exposure of workers in a ship maintenance enterprise in Guangdong Province.

Methods A total of 446 noise-exposed workers from a large ship maintenance enterprise in Guangdong Province in 2018 were selected as study subjects, and were asked about their general information and work conditions. An individual noise dosimeter was used to measure noise intensity, to estimate the equivalent continuous A-weighted sound pressure level, and then converted to a nominal 40 h working week (L_{EX, W}) and a cumulative noise exposure (CNE) for each workstation. The risk assessment method of ISO 1999:2013 was used to calculate the change of hearing threshold level and the risk of hearing loss for each workstation, followed by the risk classification according to the AQ/T 4276-2016 Guidelines for Risk Management of Occupational Noise Hazard. Pearson correlation analysis and partial correlation analysis were used to analyze the relationships of hearing loss risk with CNE and exposure years.

Results The L_{EX, W} of all workstations exceeded the national occupational exposure limit. With the increase of CNE, the positive rate of high frequency hearing loss and the risk of occupational noise-induced deafness were increased (P < 0.05). Both the levels of high frequency hearing loss of either ear and occupational noise-induced hearing loss of either ear had positive correlations with CNE and exposure years (r=0.142-0.182, P < 0.05), but there were no correlations with L_{EX, W}. The permanent hearing threshold shift induced by noise exposure of 90% workers (N₉₀) was increased with the extension of exposure years (P < 0.05) and predicted age (P < 0.01), but N₁₀ and N₅₀ had no correlations with exposure years and predicted age. The risk of high frequency hearing loss of the employees was increased with the extension of noise exposure years (r=0.721, P < 0.01), and was positively correlated with noise intensity (r=0.653, P < 0.01). The risk of occupational noise-induced deafness of the employees was increased with the extension of noise exposure years (r=0.615, P < 0.01), and was positively correlated with noise intensity (r=0.609, P < 0.01). The risk levels of various workstations were increased with the increase of exposure years.

Conclusion The noise exposure intensity of noise-exposed workstations in the selected ship maintenance enterprise exceeds the national occupational exposure limit. The risk and severity of hearing loss increase with higher CNE and extension of years of noise exposure in each workstation.