Background: Twenty-two million workers are exposed to hazardous noise in the United States. Occupational hearing loss can occur when workers are exposed to loud noise or ototoxic chemicals. The purpose of this study was to estimate the prevalence of workers with National Institute for Occupational Safety and Health (NIOSH) significant threshold shifts (NSTS), Occupational Safety and Health Administration (OSHA) standard threshold shifts (OSTS), and OSTS with age correction (OSTS-A) among U.S. industries, and to compare the prevalence across regulation criteria.
Methods: 2000-2008 audiograms for male and female workers ages 18-65, who had higher occupational noise exposures than the general population, were examined. Prevalence and adjusted prevalence ratios (PRs) for NSTS, OSTS and OSTS-A were estimated and compared across industries. McNemar’s Test comparisons were also performed to compare the estimated prevalence of NSTS to OSTS and NSTS to OSTS-A, for each demographic and industry. P-values were generated for each comparison.
Results: 20% of workers had NSTS, 14% had OSTS and 7% had OSTS-A. Industries with the highest prevalence for NSTS, OSTS, and OSTS-A were Healthcare and Social Assistance (26%, 17% and 8%), Primary Metal Manufacturing (25%, 16% and 8%), Miscellaneous Manufacturing (25%, 18% and 9%), and Real Estate and Rental and Leasing (24%, 18% and 10%).The prevalences of workers with OSTS and OSTS-A were about 66-70% and 30-33% of the prevalence of workers with NSTS, respectively.
Conclusions: After 40 years of progress in hearing conservation research and technology, current regulations should be updated. OSTS likely fails to identify a third of the workers who need intervention and OSTS-A does not identify 65-75%. Workers in the industries identified above need better engineering controls for noise and stronger hearing conservation strategies. More research is needed within "low-risk" industries to identify exposed workers and the mechanisms involved, and more effective worker training practices need to be developed.