Xenobiotics

• Xenobiotics are foreign substances, originating from outside the body, that have an action when introduced within the body, and thus have a profound impact on metabolic/ hormonal balance.
• It means that Xenobiotics are chemicals found in an organism but which are not normally produced or expected to be present in it. Best example of Xenobiotics are antibiotics in humans because the human body does not produce them itself, nor are they part of a normal diet.
• Xenobiotics is very often used in the context of pollutants such as dioxins and polychlorinated biphenyls and chemicals derived from a petroleum sources.
• Since last 50 years, xenobiotic compounds are getting added to the environment, some being highly toxic, recalcitrant and having high Bio-accumulating and Biomagnification properties.
• Xenobiotic substances are becoming an increasingly large problem in Sewage Treatment systems, since they are relatively new substances and are very difficult to categorize. Antibiotics, for example, were derived from plants originally, and so mimic naturally occurring substances. This, along with the natural monopoly nature of municipal Waste Water Treatment Plants makes it nearly impossible to remove this new pollutant load.
• Some xenobiotics such as plastics and pesticides, or naturally occurring organic chemicals such as polyaromatic hydrocarbons (PAHs) and some fractions of crude oil and coal, are resistant to degradation. Many xenobiotics produce a variety of biological effects, which is used when they are characterized using bioassay.

The Early Xenobiotic Compounds

• It was not until the early 1960s that the first landmark episode of the toxic chemical pollution was widely reported.
• In 1962, Ms. Carson reported the effect of DDT residues on the bird population. It was later proved that the pesticide was also causing troubles to humans.
• Soon afterwards, mercury poisoning was discovered along the Minimata bay in Japan, where hundreds of cases of paralysis and sensory loss were reported.
• In late 1960s, there was a reported contamination of cooking oil with polychlorinated biphenyls (PCBs) in Japan and Taiwan.
• Chemical warfare in Vietnam which included the use of the Agent Orange as defoliating agent was proved to be catastrophic on environment.