Xenobiotics are synthesized chemically organic compounds of which most do not occur in nature (Schlegel, 1995). Xenobiotics can be defined as the compounds that are foreign to a living organism. Xenobiotics include pesticides, fungicides, herbicides, insecticides, and so on. Most of which are substituted hydrocarbons, phenyl carbonates, and similar compounds. Some of these substances of which great quantities are applied to the crops and soil are very recalcitrant and are degraded very slowly or not at all.

With the introduction of xenobiotic in the environment the xenobiotic can go for following processes:
A) Biotransformation- it can be from hydrolases, enzyme induction, and mixed function oxidization.
B) It can change the biochemistry- like stress proteins, DNA, RNA, key enzymes, change in energy rates, interfere with metabolic systems.
C) Physiology and behavior- changes in chromosome and reproductive success, alter behavior, it causes tumors and teratogenic effects.
D) Change in community parameters- changes in community structure diversity, productivity, energy transfer, and succession and population density.
E) Change in population dynamics- change in productivity, reproduction, genetic and competition changes lead to ecosystem effect.

Biotic environmental fate

The interaction of a xenobiotic at the site of action in an organism is often 'molecular happen stance' i.e. xenobiotic mimic compounds which are naturally found in species that they affect - hormone mimics
- Bioaccumulation
• The storage of a compound in fatty tissue of an animal
• Result of food chain / trophic levels
- Biotransformation
• Metabolic processes, mainly by environmental bacteria, that alter the structure and toxicity of a compound
- Biodegradation
• Breakdown of a xenobiotic to CO2 and water


Examination of the fate of xenobiotics in biological systems is a natural outgrowth of man's curiosity about its environment and how it can affect society.

Following are points to consider under risk management of Xenobiotics:

A) Consider risk assessments in light of social, economic, and political needs and values.
B) Weigh costs and benefits, given both scientific and nonscientific concerns.
C) Decide whether or not to reduce or eliminate risk. Risk management take in consideration the opinion, information from private citizens, nonprofit interest groups, industry and manufacturing groups and hence managing the risk from the toxicants.

It covers the following aspects:
A) Analyzes risks quantitatively via preparing scientific data from hazard identification, extent of exposure and toxicity characterization, identify effects and associated uncertainties.
B) Measures and compares risks involved in different activities or substances
C) Helps identify and prioritize serious risks
D) Helps determine threats posed to humans, wildlife, ecosystems

It Involves:
• Dose-response analysis or other tests of toxicity
• Assessing likely exposure to the hazard (concentration, time, frequency)

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