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TOXICOLOGY
12.1 Introduction
The human body must be prepared for a daily onslaught of thousands of
chemicals. Some will be food materials (Chapter 10) that are absorbed and
metabolized because cells have membrane channels and enzymes to recognize
and deal with these compounds. Other compounds may or may not enter the
cells of the body. If they do, then the body can recognize such compounds
and must deal with them appropriately to prevent deleterious effects. It is not
always successful in this aim and many xenobiotics cause diseases and may
be fatal if a threshold dose is exceeded.
Toxicology is the study of the adverse effects of chemicals on organisms, that
is the study of poisons, where a poison can be defined as any substance that
causes injury, illness or death. Toxicology covers the study of the adverse effects
of chemicals including drugs, chemicals acquired from the environment and
toxins, which are defined here as harmful substances produced by other
organisms, often derived from microorganisms, for example the bacterial
toxins described in Chapter 2.
Xenobiotics, literally meaning ‘stranger to life’, are substances that do not
originate in the body but are pharmacologically, endocrinologically or
toxicologically active. Thus, they might be drugs or synthetic chemicals or a
substance produced in one organism and introduced into another where they
OBJECTIVES