It begins with the exposure and ends with the disease.

There is the Internal dose:  is identified by a body tissue or fluid through a lab assay, and the amount of exogenous agent can be either unchanged or metabolically altered and absorbed by the human body. (e.g. urinary lead, cotinine in urine)

Biologically effective dose: the amount of absorbed agent that has interacted with a tissue in the body. (e.g. changes in DNA strands)

Biological response and alteration: biological or biochemical changes in target cells or tissues that result from the action of the chemical and are thought to be a step in the pathological process. (e.g. in lab animals)

Disease markers: is a measurable indicator of a biological or biochemical event that either represents a subclinical stage of disease or is a manifestation of the disease itself. (e.g. tumor specific antigens, SGOT)