Is this STS work-related? ISO 1999 predictions as an adjunct to clinical judgment

Physicians and audiologists are often asked to decide whether standard threshold shifts (STSs) are work-related; epidemiological data can inform these decisions.

Predictions of ISO (2013) for both age-related and noise-induced threshold shifts, for the 2, 3, and 4 kHz average used in calculating OSHA STSs, are presented, in tables, graphs, and an Excel spreadsheet calculator. Specifically, the ISO 1999 model estimates age-related thresholds based on age and sex; it estimates noise-induced threshold shifts based on noise level and duration. It specifies that to estimate the final hearing thresholds for a person of given percentile, age, sex, and noise exposure, the expected age-related threshold is to be added to the expected noise-induced threshold shift. Examples show how these data can predict the relative contributions of aging and occupational noise to an STS.

Early-career STSs, especially with high levels of noise exposure, are more likely to be primarily noise-induced. After the first decade of exposure, most STSs will be primarily age-related.

Given a worker's age, sex, and occupational noise exposure history, ISO 1999 estimates of the expected contributions of aging and noise can supplement clinical judgment.