Occupational Noise-Induced Hearing Loss in Indian Black Tea-Processing Factories: Assessing the Prevalence and Associated Factors of an Overlooked Problem.

Background Occupational noise-induced hearing loss (ONIHL) is an important occupational health problem, but evidence among workers in the Indian tea-processing industry remains limited. This study aimed to estimate the prevalence of ONIHL, characterize workplace noise exposure across occupational job stations, and examine factors associated with ONIHL among workers in black tea-processing factories in Darjeeling district, West Bengal, India. Methods A cross-sectional study was conducted from February 2022 to April 2025 among 312 workers from six black tea-processing factories in Darjeeling district. The factories were selected by convenience sampling, followed by simple random sampling of eligible workers within participating factories. Sociodemographic and occupational information was collected using a structured questionnaire. Participants underwent otorhinolaryngological examination and pure-tone audiometry, while workplace sound levels were assessed across occupational job stations and expressed as eight-hour equivalent continuous A-weighted sound levels (Leq,8h). Multivariable logistic regression was used to examine factors associated with ONIHL after adjustment for age, sex, duration of employment, and job station. Results The mean age of participants was 34.1 ± 9.6 years, and 241 (77.2%) were male. ONIHL was identified in 90 of 312 workers, giving a prevalence of 28.8% (95% CI: 24.1-34.1%). The highest ONIHL prevalence occurred in the crushing-tearing-curling (CTC) room (44.8%), maintenance section (37.5%), and withering room (28.2%), which also recorded the highest Leq,8h values of 85.3, 85.1, and 80.7 dBA, respectively. After adjustment, significant associations were observed for the CTC room (adjusted OR (AOR) = 33.968; 95% CI: 8.606-134.074), withering room (AOR = 27.514; 95% CI: 5.743-131.816), maintenance section (AOR = 13.431; 95% CI: 2.478-72.798), combined sorting and packing category (AOR = 9.030; 95% CI: 1.766-46.161), and increasing age (AOR = 1.084 per year; 95% CI: 1.028-1.142). Male sex was not statistically significantly associated with ONIHL (p = 0.060). None of the workers was observed wearing hearing-protection devices during workplace assessment. Conclusions ONIHL was common among workers in the participating black tea-processing factories and varied substantially across occupational job stations, with the highest prevalence occurring in areas with the greatest measured workplace noise exposure. Occupational job station and increasing age were significantly associated with ONIHL, although several workstation-specific adjusted estimates were imprecise and should be interpreted cautiously. The absence of observed hearing-protection use highlights an important gap in occupational hearing-safety practices. Workstation-focused hearing-conservation measures, including noise monitoring, audiometric surveillance, engineering and administrative controls, worker education, and consistent use of hearing-protection devices, should be considered.