ABSTRACT
This chapter details the importance of the dose, the route, and the duration and frequency of exposure to a chemical. It describes what happens when a chemical enters the body via different ports of entry and explains why the liver plays an important role as a checkpoint. It also stresses the difference between short-term (acute) and long-term (chronic) exposure and its consequences for the toxic response. The mere presence of a potentially harmful chemical is not sufficient to gauge a risk; besides the hazard, the exposure must be factored in. Why exposure plays a key role in assessing human health risk is exemplified by a ubiquitous chemical present in consumer products.
