The framework for considering Traditional versus Green Jobs and Old versus New Occupational Hazards can be expressed in a simple 2 x 2 matrix. In Traditional jobs there are occupational hazards which have been studied and characterized; this category is what we know.  In some cases Traditional jobs are being performed with newer technologies and thereby introduce newer hazards that require additional efforts to characterize and address them; this category is what we know we don't know. A third category occurs at the intersection of our knowledge of Old Hazards as it potentially applies to newer Green Jobs and technologies; this category is what we don't know we know. Finally, the fourth category is typified by new Green Jobs and New Hazards that may not have been identified or characterized; this category is what we don't know we don't know.
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