Xenobiotic Distribution: A Comprehensive Review and Toxicological Implications

Xenobiotics is derived from the Greek words ‘Xenos’, meaning foreign and strange, and ‘bios’, which means life. Concerning the environment, xenobiotics can be defined as chemically synthesized compounds that do not occur in nature and thus are ‘foreign’ to the biosphere. Relating to the organisms, a xenobiotic is any substance foreign to life/living organism. Thus, a xenobiotic is a foreign chemical substance found within an organism that is not naturally produced by or expected to be present within the organism.  The definition of xenobiotics as compounds ‘foreign to life’ exhibiting unnatural structural features does not necessarily mean that they are toxic compounds, but many are indeed harmful to living organisms. Specifically, drugs such as antibiotics are xenobiotics are xenobiotics because the human body does not produce them itself, nor are they part of a normal food. Natural compounds can also become xenobiotics if another organism takes them up. The body removes xenobiotics by xenobiotic metabolism, which consists of their deactivation and excretion, which happens mostly in the liver. Enzymes are involved in the metabolism of xenobiotics. Excretion routes are urine, feces, breath, and sweat. Xenobiotics may be grouped as carcinogens, drugs, environmental pollutants, food additives, hydrocarbons, and pesticides.