Mary M. Prince
Randall J. Smith
Steven Gilbert
Leslie T. Stayner
Natl. Inst. for Occupational Safety and Health NIOSH), 4674 Columbia Pkwy. C-15, Cincinnati, OH 45226
Occupational hearing conservation programs (HCPs) have been implemented in many industries in accordance with the 1983 OSHA hearing conservation amendment. The availability of these longitudinal databases permits an examination of associations between changes in hearing levels with other variables, including noise exposure. This paper examined (1) whether there is an increased risk of NIHL from exposures below 85 dBA; (2) whether workers with noise exposures above 85 dBA who are required to use hearing protection still have an increased risk of NIHL compared to low-noise-exposed (less than 70 dBA) workers; and (3) how risk may depend on the type of hearing protection used and reported degree of compliance. The data used in this analysis include most of the data analyzed by the ANSI working group to examine hearing conservation program effectiveness. Variables included age, sex, race, type of hearing protection, industry code, and hearing threshold levels (for both ears, tested at 0.5, 1, 2, 3, and 6 kHz). Databases for comparison included both internal and external ``control'' groups with low-noise exposure, as well as noise-exposed populations in which either the hearing conservation program was highly effective and/or the population was well protected via good hearing protection compliance.