EP617 NOISE-INDUCED HEARING LOSS IN SMALLSCALE INDUSTRIES IN POKHARA, NEPAL: A CROSS-SECTIONAL PREVALENCE STUDY Michael Smith1, Tim Robinson2, Joshua Whittaker2, Aanand Acharya3, George Dowswell4, Devesh Singh5 1 ENT 2 Department, Worcestershire Royal Hospital, UK College of Medical and Dental Sciences, University of Birmingham, UK 3 ENT Department, University Hospitals Birmingham, UK 4 Primary Care Clinical Sciences, University of Birmingham, UK 5 ENT Department, Western Regional Hospital, Pokhara, Nepal INTRODUCTION • • • • • Noise-induced hearing loss (NIHL) is an irreversible sensorineural hearing impairment characterised by high frequency (3−6 kHz) hearing loss. Consequences include social isolation, impaired communication, increased injury risk and reduced productivity for employers. Risk of NIHL increases with magnitude and duration of noise exposure. Regular exposure to >85 dBA considered hazardous to hearing. WHO estimate 16% of adult-onset hearing loss in South-East Asia attributable to occupational noise. NIHL in Nepal • Joshi et al. studied environmental NIHL in Kathmandu. Retrospective cohort: cases exposed >70dbA (n=36), controls <55 dBA (n=25). OR=4.2 (4.0 when adjusted for occupational noise). • No previous occupational NIHL research identified. • Economically active population = 16.6 million. • >95% work informally; not covered by occupational health and safety legislation. • Substantial proportion at risk of NIHL. • Need for research to support generation of noise permissible exposure limit (PEL) legislation. Aim To assess occupational noise exposure, hearing thresholds and NIHL prevalence in two small-scale industries in Pokhara, Nepal, and compare to non-exposed controls METHODS AND MATERIALS • • Cross-sectional prevalence study based in Pokhara, Kaski District. – Conducted between February and April 2012. Convenience sampling of workplaces: − Metal and wood workers (exposed groups). − Hotel workers (control group). Exclusion Criteria • • • • Aged <15 years. Working in current occupation <6 months. Current bilateral outer/middle ear pathology. Permanent bilateral hearing loss preceding occupational noise exposure. Assessment Protocol • Noise exposure: Average workplace noise (LAeq) measured over 1 hour and extrapolated to an 8-hour working day (LAeq,8h) for each participant. • All consented individuals received: – Hearing and occupational history questionnaire. – Otoscopy (exclusion/inclusion confirmed by ENT referral where necessary). – Air-conduction audiometry at 0.5, 1, 2 and 4 kHz. • Those with a single ear average threshold >25dBHL OR >25dBHL at 4kHz, proceeded to: – Air-conduction audiometry at 3, 6 and 8 kHz. – Bone-conduction audiometry at 1, 2 and 4 kHz. – Masked thresholds where necessary according to British Society of Audiology standards. • Peak threshold between 3-6kHz (‘notch configuration’) = NIHL. Stage 1: Questionnaire Stage 2: Otoscopy Stage 3: Audiometry Consent n=487 Met Exclusion Criteria Withdrew Consent Included n=122 n=359 n=6 Lost to Follow Up n=28 Proceeded to Audiometry n=331 Excluded after Audiometry n=4 Final Dataset n=327 Metal Wood n=99 Hotel n=124 n=104 RESULTS - Demographics Demographic Data Hotel Workers Metal Workers Wood Workers Difference (Kruskal-Wallis or chi-squared) n 104 99 124 - Age – median years (IQR) 26.5 (21−35) 24 (21−38) 25 (20−36) Non-significant P= 0.854 Gender – % males 76.92 98.99 100.00 Significant P<0.001 34.62 48.48 39.52 (0, 0−0.40) (0, 0−0.95) (0, 0−0.18) Significant P= 0.003 4 (2−12) 4 (1.5−12) 6 (2−15) Non-Significant P=0.191 Smoking – % (median packyears, IQR) Time in occupation – median years (IQR) • • • • • 67.15% of recruited completed assessment Sample from 17 hotels, 13 metal works and 15 wood works All continuous data non-normal (K-S test) 82.26% had a smoking history of <1 pack-year with 4.28% ≥ 5 pack-years 50.15% aged ≤ 25 years; 89.60% ≤45 years RESULTS – NIHL Prevalence NIHL Difference prevalence (Chi-squared) (%) Population n Hotel Workers 104 5.05 Metal Workers 99 35.35 Hotel Workers 104 5.05 Wood Workers 124 27.37 Odds Ratio (95% CI) Significant P<0.001 17.83 (5.53−57.51) Significant P<0.001 11.46 (3.68−35.70) RESULTS - continued • • • • Significant difference in average hearing threshold distribution between controls and exposed (medians = 11.25 dBHL vs. 17.50 dBHL; P<0.001). Non-significant difference in distribution between exposed groups (medians = metal 16.88 dBHL vs. wood 18.10 dBHL; P=0.403). LAeq,8h distribution significantly different between controls and exposed (medians = hotel 59.10 dBA, metal 80.56 dBA, wood 85.10 dBA; P<0.001). Noise levels ranged between 51.4−68.6 dBA at hotel sites, 65.3−84.7 dBA at metal sites and 71.2−93.9 dBA at wood sites. All odds ratios generated through binary logistic regression, adjusted for age and time in occupation. All other demographics were non-significant in predicting risk of NIHL. Odds Ratio for risk of NIHL for any exposed vs. control = 13.44 (95% CI= 4.69−38.54). Average Hearing Threshold (0.5, 1, 2, 4kHz) (dBHL) 60 Hotel Workers Metal Workers Wood Workers 50 40 R² = 0.2505 30 R² = 0.1474 R² = 0.2559 20 10 0 10 20 30 40 50 Age (Years) 60 70 Plot of average hearing threshold against age, showing increased hearing thresholds in noise-exposed groups DISCUSSION • As expected, occupational noise exposure, hearing thresholds and NIHL prevalence significantly higher in metal and wood industries. – – • • • Young age distribution and short exposure time may mask true disability associated with NIHL. Significant differences in smoking level, but low pack-years so unlikely to significantly impact on hearing. Lack of comparable results as previous studies in small-scale workshop industries recruited significantly smaller samples. Industrialisation and a growing economically active population in Nepal likely to put further people at risk. Occupational health and safety guidelines currently provide minimal protection for workers. Limitations • Convenience sampling reduces generalisability of results. • Workplace noise assessment did not account for variation in noise exposure levels caused by powercuts, compromising validity of LAeq,8h as comparator. • Inability of data collection tool to standardise noise exposure and hearing history. CONCLUSIONS • Workers in small-scale metal and wood industries appear to be at significantly higher risk of NIHL, compared to control subjects. • There is a need for hearing conservation policies to cover a growing workforce in Nepal. • These measures may alleviate the effects of a widespread, yet preventable hearing impairment. References 1. Concha-Barrientos et al. Occupational noise: assessing the burden of disease from work-related hearing impairment at national and local levels. WHO Environmental Burden of Disease, No 9. Geneva, WHO (2004) 2. Nelson et al. The global burden of occupational noise-induced hearing loss. American Journal of Industrial Medicine (2005) 48(6):446-458 3. Joshi et al. Environmental noise induced hearing loss in Nepal. Kathmandu University Medical Journal (2003) 1(3):177-183 4. International Labour Organisation. Labour and Social Trends in Nepal 2010. Geneva, ILO (2010) • This study was carried out as part of the International Health course at the University of Birmingham, UK. • Logistical support was provided by the International Nepal Fellowship. • The authors report no conflicts of interest.