Excess risk estimates of hearing impairment of Indian professional drivers

Noise and vibration are occupational hazards that affect worker health and safety. Prolonged exposure to noisy environment results in hearing loss of the affected individuals. The objective of this study was to estimate an excess risk of hearing impairment of professional drivers in Kolkata city of India. In this study, 90 healthy male subjects of similar age, height and weight were equally sampled in three separate sub-samples of 30 subjects each viz. drivers with less than 10 years of occupational noise exposure, drivers with more than 10 years of occupational noise exposure and office workers as control. The audiometric testing of both ears of the selected subjects was conducted at frequencies of 0.125, 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8 and 10 kHz. The average estimated excess risks of hearing impairment of the subjects were calculated from audiometric data using five standard model equations. The hearing threshold levels of office workers at audiometric test frequencies of 0.5, 1, 2 and 3 kHz did not exceed 25 dB (A) to cause hearing handicap. However, it exceeded 25 dB (A) for professional drivers (10 years of noise exposure). The values of estimated average excess risk indicated that hearing damage of professional drivers was expected to occur sooner at 3 and 4 kHz frequencies than losses at lower frequencies. It was concluded that the occupational hazards of professional driving significantly increased hearing threshold levels of drivers as compared to office workers. This study emphasizes the need to periodically check professional driver's hearing to determine their auditory threshold shift or excess risk, especially those working in noisy environments. It highlights an urgent need to take up some interventions to reduce the harmful effect of loud traffic noise to drivers exposed to noisy environment in populated cities.