Xenobiotics: Persistent Organic Pollutants

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Chapter 01: Introduction

1.1. Xenobiotics
The term xenobiotic is derived from Greek words, “xenos”, meaning strange or foreign, and “bios”, meaning life. Thus xenobiotics are exogenous chemicals which includes natural and synthetic chemicals. These can be pesticides, chemical vapors from automobiles, industrial chemicals, plastics, secondary plant metabolites, toxins produced by plants, molds and animals, food additives etc. Xenobiotics are considered as pollutants, but all the pollutants are not considered as xenobiotics. Persistent Organic Pollutants (POPs) such as dioxins, polychlorinated biphenyls (PCBs) are considered as xenobiotics. Drugs and antibiotics are specified as xenobiotics in human body.

1.2. Consequences of Xenobiotics
Accumulation
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This can cause increased vulnerability of human body to cancers and autoimmune diseases. Endocrine alteration of humans and wildlife is also associated with the intensification of xenobiotics level. Pharmacological investigations have been shown that alteration of multiple hormonal systems relate with the exogenous compounds. Persistent organic pollutants such as dioxins, polychlorinated biphenyls can modulate the activities of several different hormones. Accumulation of these compound in living beings can cause birth defects, tumors, immunotoxicity, changes in metabolism and finally resulting death. Due to the rapid growth and development unborn children or the neonates are more expose to the environmental xenobiotics. Environmental xenobiotics are associated with the disruption of reproductive systems of wild animals. The emissions of coal based power stations include certain amount of xenobiotics that result in health problems, even death. In United States coal pollutants contribute to the four of the five leading severe diseases; heart diseases, cancers, stroke and lower respiratory disorders.

1.3. Sources of Xenobiotics
1.3.1. Direct sources
Waste water and solid residual releases from the industries are major direct sources of xenobiotics. These industries can be pharmaceutical, plastics, paper and pulp, textiles, pesticides
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Degradation of these hydrocarbons using physico- chemical processes result in harmful compounds which further disturb the environment.
1.3.1.4. Paper and Pulp effluents
Chlorinated organic compounds are synthesized during bleaching process which are harmful to ecosystems. This phenomenon can be worsening if these compound are released to the anaerobic environments. Certain anaerobic bacteria can methylation these compounds which cause deleterious effect to higher animals.
1.3.1.5. Dyes
Persistence of xenobiotics is a major result of dye agglomeration. Dye agglomeration affect to the photosynthesis in the aquatic bodies due to the reduction of light penetration even at low concentrations. Azodyes, anthraquinone and phthalocyanine are commonly used in textile, paper and photographic industries. Degradation of these dyes produce aromatic amines, which are carcinogenic and mutagenic.
1.3.1.6. Pesticides and Insecticides
Organophosphorous compounds, benzimidazoles and morpholine are widely used as pesticides and insecticides. Due to slower degradation these are contribute to the environment pollution.
1.3.1.7.

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