JOB-EXPOSURE MATRICES

During the last years, the use of Job Exposure Matrices (JEMs) for the evaluation of past occupational exposures has grown. This approach is described in this paper. The definition of a JEM is provided. The dev elopment process of a JEM is discussed It includes the choice of the j ob classification system which influences the degree to which the matr ix can be used in other studies, the precise definition of exposures a nd the choice of entries which should provide more information than th e oversimplified exposed/non exposed dichotomy. When comparing JEMs an d experts' evaluation of exposure, all aspects of both methods have to be looked at and a balance struck between the advantages and shortcom ings of each of them. The problem should not be reduced to a single ch oice between the precision provided by experts, and the cost savings a nd standardization offered by JEMs. Statistical analysis with a JEM mu st be adapted to the job classified information it provided. When an a ppropriate method is used, the loss of power with a JEM compared to ex perts' evaluation is rather small or even null. Finally, it is importa nt to avoid a systematic opposition between JEMs and expert assessment s, as one positive result of their comparison may be the improvements of both methods of exposure evaluation.