Hearing threshold levels among steel industry workers in Samut Prakan, Thailand

BACKGROUND: Industrial noise is generally considered from the perspective of environmental health and safety, with requirements for reduced occupational noise exposure, strict standards for hearing protection, and public health awareness campaigns. MATERIALS AND METHODS: This cross-sectional study aimed to identify the hearing threshold levels (HTLs) among steel industry workers exposed to hazardous noises in Samut Prakan Province, Thailand, and investigate the associations between hearing loss and age and length of employment in the industry. Audiometric data for 93 participants were collected at the Samut Prakan Provincial Hospital. Qualified technicians performed audiometric screening using an audiometer in a quiet environment. Tests were conducted after participants had completely rested for ≥14 hours after the last exposure to workplace noise. RESULTS: The results showed that all participants had been employed in a work zone with a noise hazard for >1 year. Participants’ age ranged from 19 to 59 years and their work experience from 1 to 39 years. Average mean hearing thresholds in the right ear at 4, 6, and 8 kHz were 31.34, 29.62, and 25.64 dB, respectively. Mean hearing thresholds in the left ear at 4, 6, and 8 kHz were 40.15, 32.20, and 25.48 dB, respectively. Hearing loss related to work experience was greater than that attributable to age and work station. Duration of noise exposure ranged from 1 to 39 years, and more than half of the participants (60.2%) were exposed to hazardous noises from 6 to 25 years. CONCLUSION: These findings show that participants’ age and experience were significantly associated with hearing loss at all levels. HTLs among industrial workers should be regularly assessed. At the health policy level, these workers need to start being protected when they begin working.