Evaluation of Noise Levels and Noise-Induced Hearing Loss of Workers at a Stone Milling Factory in Nakornsithammarat Province

Abstract

The cross-sectional study was conducted to describe the noise levels and it’s frequency inastone milling factory’s working environment. Employee noise exposure in each job characteristic were measured and then the audiometry of all 50 employees were examined to diagnose the occupational noise-induces hearing loss (NIHL). The working environment risk assessment questionnaire was used to evaluate the noise control methods in stone milling factory.

The results of the study : 1) showed that noise frequency in both small and large stone milling plants in range of 250-10,000 Hz exceeded the noise level standards (85 dBA) set by the Department of Labor Protection and Welfare 2010 CE., 2) There were 22% of workers exposed to noise level ≥ 85 dBA which worked in crushing and quarrying of stone and electrical job. Measurement of the impact noise level by work type showed that the workers who experienced the most impact noise were electrical workers (147.20 dBpeak). While, loading truck drivers, engine controllers, 10 wheeled truck drivers, office workers, maintenance workers, diggers, and crushing and quarrying of stone workers had an impact noise level of between 134.9-139.54 dBpeak, which did not exceed OSHA standards of 140 dBpeak., and 3) Audiometry results were interpreted using Bureau of Occupational and Environmental guideline for diagnosis of NIHL. 30% of NIHL found in employees who work at the quarry, office, crushing and quarrying, maintenance, and safety and environment department. While 22% of employees experienced noise levels ≥ 85 dBA were diagnosed as NIHL. The work environment risk assessment found inside the plant, rock blasting, machinery, and machinery maintenance departments had noise control measures which passed standard criteria announced by the Department of Primary Industries and Mines. This giving stone milling plants a system to protect environmental impact under the Factories Act 1992 CE. Therefore, the annually noise monitoring and health surveillance program should be conducted in stone milling factories and thecontinuous hearing conservation program should be provided to prevent NIHL of stone milling’s workers especially the workers who exposed to noise frequencies and impact noise exceed the standard.