Xenobiotics is the study of how an
animal processes, on a chemical level, substances
foreign to the body, excepting food. The word can refer either to the study or to the substances themselves, such that it is possible to say that Xenobiotics concerns xenobiotics without implying any
self-referental nature on the part of the
discipline. This should tell you something about the sort of people who work in the field. Generally the term is used interchangably with "
toxicology." For this writeup, I shall capitalize Xenobiotics when referring to the field.
One fascinating part of the study is the discussion of p-450 enzymes, a class of enzymes found most predominatly in the liver, but also existing kidneys, small intestine, lungs, et al. P-450 enzymes are responsible for a large amound of xenobiotic metabolism and are extremely unstable when not in a living cell or when above ~-77 degrees Celcius.
Most largely covalent xenobiotics are metabolized in two stages: the first stage will attach a molecule to the xenobiotic renendering it water soluble, while the second will do the dirty work of ridding it from the body.
An excellent book for learning about Xenobiotics can be found in Cassel & Hewett's Handbook of Toxicology. The fourteenth chapter may be especial interest, and the whole tome is very accessible. Look in your local medical library or research library.