| Introduction: Hearing loss and tinnitus were the most frequently occurring service-connected disabilities for fiscal year 2013 combining to account for 1.7 million cases and a cost of ;Objectives: Evaluate the association between exposures to metals and hearing loss in Naval Shipyard personnel while controlling for noise, organic solvents, and other major risk factors.;Methods: Data for 1,546 personnel aged 18-77 from the years 2004-2015 were analyzed. Hearing threshold changes were computed across the 500-6000 Hertz (Hz) frequencies. A Permanent Threshold Shift (PTS) was defined as an average 10 decibel (dB) change across the 2000, 3000, and 4000 Hz frequencies. Noise and chemical exposure records were used to assign personnel into one of five exposure groups based on level of concentration: (a) high noise, (b) high metals/solvents, (c) high metals/noise, (d) high metals/solvents/noise, and (e) low metals/solvents/noise (reference group). Specific chemicals targeted for analysis included lead, cadmium, arsenic, toluene and xylene.;Results: Logistic regression indicated high concentrations of metals and solvents had an Odds Ratio (OR) = 2.4 and 95% Confidence Interval (CI) 1.016, 2.846. The metals, solvents, and noise group had an OR=1.7; 95% CI 1.462, 3.944. Both groups were significantly associated with development of a PTS while controlling for age, gender and exposure duration. Kruskal-Wallis and Mann-Whitney U tests did not reveal significant hearing loss differences between metal, solvent and noise exposure combinations. However, hearing thresholds were significantly worse with increasing age and in males compared to females (p<.05). Odds of PTS development increased 6.8% for every year of age (OR=1.068; 95% CI 1.053, 1.083).;Conclusions: Personnel with simultaneous exposures to high concentrations of metals such as lead, cadmium, and arsenic and solvents such as toluene and xylene beginning at concentrations less than the Occupational Safety and Health Administration's Permissible Exposure limits and in combination with noise may damage hearing. |
