Occupational Noise Exposure and Hearing Loss in Truck Drivers: A Cross-sectional Analytical Study in Iran

Drivers have a significant role in transporting and moving goods using heavy vehicles. These drivers are exposed to various complications including hearing loss, due to long journeys and constant exposure to road noise. Considering the importance of preventing hearing loss, this study was conducted to determine the occupational exposure of truck drivers to noise and its effect on noise‑induced hearing loss.

This cross‑sectional‑analytical study was conducted on 692 truck drivers of 16 types of heavy vehicles in Iran. The hearing status of the truck drivers was measured in the right and left ears using a Welton 1300 clinical audiometer in a soundproof room based on the guidelines provided by the American Speech–Language–Hearing Association. The equivalent sound pressure level (LAeq) in the truck driver’s cabin was measured by a sound meter with a CEL‑440 analyzer model and according to the standard (ISO 9612 1997) in A‑frequency weighting. Finally, using SPSS V‑26, the prevalence of hearing loss, the amount of hearing loss in different frequencies, and its relationship with exposure to noise in different frequencies were investigated.

The mean ± standard deviation LAeq in the examined truck was determined as 75.89 ± 5.98. The highest average LAeq was related to the frequency of 500 Hz with 62.76 dBA. The average LAeq was generally higher at lower frequencies (250, 500, and 1000). The prevalence of hearing loss in the right and left ears was estimated at 59.98% and 64.74%, respectively. The highest average hearing loss in the right and left ears was related to 6000 and 8000 Hz frequencies. There was a statistically significant difference between the LAeq inside the truck’s cabin with hearing loss compared to people without hearing loss in the right and left ears (P < 0.001). A statistically significant relationship between LAeq at different frequencies in different truck brands with hearing loss at different frequencies in the right and left ears was observed in the majority of trucks in reverse (P < 0.05). A significant relationship was observed between age and work experience with hearing loss in the right and left ears (P < 0.001).

Truck drivers suffer from a high level of hearing loss which is very similar to any industrial worker with high frequencies such as 4000 and 6000 Hz. Despite the lack of frequency relation between noise and hearing loss, increasing age, work experience, and noise exposure, regardless of frequency, can lead to increased hearing loss in these truck drivers, especially in the left ear. The appropriate cabin design, regular maintenance of vehicles, use of personal protective equipment, reduction of driving hours, and periodic annual examinations of drivers are suggested to prevent further progress of hearing loss in them.