FIGURE 1—

Conceptual models delineating PRF and ORF effects.

Note. ORF = occupational risk factor; PRF = personal risk factor. Model 1 depicts a model in which the PRF and ORF are independent of each other with respect to their impact on disease. Models 2, 3, and 4 present a framework in which PRFs and ORFs can have interaction effects on disease. In models 2 and 3, PRFs and ORFs affect the same disease or disease stage, whereas in model 4 risk factors can affect different diseases or disease stages that can affect each other or disease stages that can exacerbate or compound the disease. In some cases, placement of examples in one model versus another can change on the basis of scientific information or interpretation of that information. References to disease may also include injury.