Environmental and occupational epidemiology are the last two branches of epidemiology discussed in this lecture. Both branches are oriented primarily towards the study of causative exposures, rather than of the disease outcome. Occupational epidemiology is closely related to environmental epidemiology in that many of the environmental contaminants of concern are man-made products or by-products. Therefore, certain occupational groups are often subject to the same type of contaminant insults as the general public is, although the levels of exposure that they receive are likely different. Workers and users will receive the exposure during manufacturing or handling of the products. On the other hand, the general public will be exposed to the products or their by-products when these contaminants have been emitted, spread, or otherwise precipitated into the environment.

The exposures to environmental and occupational health hazards are the domain of health risk assessment because they are not only of great concern to the public, but also thought to be highly preventable. It is under this notion that several health statutes have been passed in the United States (and in other industrial countries) to regulate the exposures to these types of health hazards. A brief description of these health statutes was presented in Lecture 3.

Of all branches of epidemiology, occupational epidemiology tends to use biomarkers the most to monitor human exposures. This is because occupational groups are relatively easier to be identified, worked with, and followed up.