Occupational noise mapping and exposure assessment in a steel factory (Case study: Bandar-Anzali Steel Ingot Factory, Iran)

There are a wide range of equipments and machinery in the steel ingot industry, and most of them, are a source of noise pollution. The purpose of this study is to determine the main sources of noise, the daily exposure of labors and to investigate the noise-induced hearing loss (NIHL) prevalence in Anzali Steel Ingot factory. After a walk-through survey of existing units and the factory work schedule, 21 sampling points were selected in the process, office and service units of the factory. The field measurements were conducted at specific hours of two different work-shift days using a portable sound pressure level (SPL) meter. Noise map of the factory revealed that in almost 68% of job groups in the factory, daily-averaged noise level is greater than the occupational exposure limit (OEL). Also, the daily-averaged exposure of workers in all process units was more than the limits. Workers in furnace installation, electricity and facility units experienced the highest exposure with a daily exposure of more than 100 dB(A). A significant correlation was observed between the daily exposure level and NIHL (p-value=0.022) at α=0.05 significance level. The NIHL in the process units increased between 1.25 and 7.5 dB(A), annually. The maximum increase was observed at units whose workers' noise exposure was within 5 dB(A) of the exposure limits, due to not using personal protective equipment (PPE). The daily exposure of the workers, who spend at least 25 % of daily working time in the furnace installation area, was above 100 dB(A), despite regular wearing of earplugs. Due to the ineffectiveness of the exposure time reduction, the best solution for these workers is to increase the noise reduction coefficient of the chamber's walls in the furnace installation unit, installing barriers in the furnace installation open area and increasing the number of chambers. In other process units, full inspection of the regular wearing of the PPE over a period of time is recommended. Thereafter the hearing loss of workers should be checked again and in case of inefficiency, changing the workplace of workers in different process units is recommended to reduce the exposure.