Assessment of occupational noise generation and associated noise-induced hearing loss among employees of a black tea processing factory in Darjeeling District, India

Introduction: Exposure to high levels of noise is a problem among tea factory workers worldwide, but it is poorly studied in India. Aims: This study aimed to assess noise generation in various parts of a black tea factory and find out prevalence of occupational noise-induced hearing loss (ONIHL) and its determinants among employees. Materials and Methods: An observational cross-sectional study was performed in a black tea processing factory of Darjeeling District. Noise levels and exposure data at different parts of the factory were measured using a sound level meter. Participant characteristics were obtained using a questionnaire and noise-induced hearing loss data obtained by audiometry. A sound map was generated based on noise exposure data and a multivariable logistic regression performed to assess determinants of ONIHL. Results: Sound pressure levels ranged from 58.7 to 90.3 dBA, with the highest levels in the crushing-tearing-curling (CTC) room. Noise exposure of workers was the highest during curling process and the lowest during packaging in the packing room. The prevalence of ONIHL was found to be 28.3%, most of which were of moderate degree, and the highest prevalence was among CTC room workers. Multivariable analysis showed significant association only between daily noise exposure and the presence of ONIHL (AOR 1.68, P value = 0.018). None of the study participants used any hearing protection equipment during work. Conclusions: Generation of high levels of noise is a pertinent problem in the black tea factory, which, coupled with non-use of personal protective equipment, led to a high risk and prevalence of ONIHL.