For these chemicals the skin can act to limit the chemical's entry into the body. Other chemicals are readily absorbed by the skin which serves as a sponge, especially when the toxic solvent soaks clothing, gloves, or shoes, which serve as a continuously repeating application. Recent studies by dermatologists at the University of California confirm that skin absorption is a major route of entry. Dioxins and PCBs are readily found in fat samples. An important concept is the distinction between exposure and dose.
Exposure is the amount of chemical the body contacts externally.
But all does not necessarily enter the body. Dose is the amount of chemical that actually penetrates into the body, and the effective dose ultimately determines toxicity. Distribution refers to the dynamic movement and temporary storage of a chemical within the body. Virtually every chemical has a defined target organ, of which the most common are the brain, heart, lungs liver, kidney, and colon. Different kinds of tissues and organs take up and release chemicals at different rates.