Objectives: This study was undertaken to compare the operating characteristics of the Hoar et al job-exposure matrix and the job-exposure matrix of the National Occupational Hazard Survey (NOHS) of the National Institute for Occupational Safety and Health in the United States. Both matrices were applied to occupations in the metal, paper and wood, and chemical, drug and paints industries, and the extent of agreement between the two was estimated.
Methods: The agents (exposure entities) selected for the comparison were common to both matrices; altogether 214 agents were included. For the comparison of occupations, the occupational codes of the Hoar et al matrix were converted to those of the NOHS-based matrix. For every occupational group analyzed, each of the 214 exposure entities was classified as to its "presence" or "absence", and a kappa statistic (kappa) was calculated.
Results: The kappa(i) ranged from 0.27 to -0.12. In general, most of the agreement between the 2 matrices occurred because they agreed as to the absence of exposure for the exposure entities. Variation in agreement was observed for both the individual exposure entities and for chemical families.
Conclusions: These results indicate poor to only fair agreement between the 2 job-exposure matrices, and they underscore the importance of understanding the rules for classifying exposures when any such matrix is used. Investigators also need to be aware of the methods and limitations of the occupational coding systems.