Xenobiotics bioaccumulation

Trabalka JR, Garten CT Jr. 1981. Development of predictive models for xenobiotic bioaccumulation in terrestrial systems. Oak Ridge, TN Oak Ridge National Laboratory, Environmental Sciences Division 2037. ORNL-5869. 

Keizer, J., G. D Agostino, and L. Vittozzi. 1991. The importance of biotransformation in the toxicity of xenobiotics to fish. I. Toxicity and bioaccumulation of diazinon in guppy (Poecilia reticulata) and zebra fish (Brachydanio rerio). Aquat. Toxicol. 21 239-254. 

Historically, organic environmental pollutants were hydrophobic, often persistent, neutral compounds. As a consequence, these substances were readily sorbed by particles and soluble in lipids. In modern times, efforts have been made to make xenobiotics more hydrophilic - often by including ionisable substituents. Presumably, these functional groups would render the compound less bioaccumulative. In particular, many pesticides and pharmaceuticals contain acidic or basic functions. However, studies on the fate and effect of organic environmental pollutants focus mainly on the neutral species [1], In the past, uptake into cells and sorption to biological membranes were often assumed to be only dependent on the neutral species. More recent studies that are reviewed in this chapter show that the ionic organic species play a role both for toxic effects and sorption of compounds to membranes. 

Connell, D. (1990). Bioaccumulation of Xenobiotic Compounds. CRC Press, Boca Raton, FL. 

Butte, W. (1991) Mathematical Description of Uptake, Accumulation and Elimination of Xenobiotics in a Fish/Water System, In Bioaccumulation in Aquatic Systems Contributions to the Assessment (eds. Nagel, R. and Loskill, R.), VCH, Weinheim. 

Chlorinated micropoUutants are harmful for man and environment due to their toxicity, persistence, and bioaccumulation. Persistent compounds are very stable and difficult to get metabolized and mineralized by biological and chemical processes in the environment, and as a result, they have become ubiquitous in water, sediments, and the atmosphere bioaccumulation is the result of the lipophilicity of these compounds. Polychlorinated dibenzodioxins and -furans (PCDD/F) are not produced purposely like many of other chlorinated technical products, such as chlorinated biocides DDT, lindane, and toxaphene. The production and use of persistent organic pollutants (POPs), the dirty dozen has now been banned worldwide by the Stockholm protocol. It should be mentioned that about 3000 halogenated products have now been isolated as natural products in plants, microorganisms, and animals," but the total amount of these products is much smaller compared to xenobiotics. 

Bioaccumulation is defined as the uptake of xenobiotics and their retention by living organisms. Bioconcentration is the term applied to the uptake and retention of xenobiotics by organisms from their immediate environment. Biomagnification is the term applied to uptake and retention of xenobiotics from food. 

Studies on the bioaccumulation of xenobiotics should parallel the chemical qualification of the environmental compartment surrounding the organism. The concentration technique (natural and physicochemical) plays a crucial role. 

Connell DW (1990) Bioaccumulation of xenobiotic compounds. CRC, Boca Raton... 

Bergman, and W.H. Benson, Eds., SETAC Special Publication. CRC Press, Boca Raton, FL. Bioaccumulation of Xenobiotic Compounds. 1990. D.W. Connell. CRC Press, Boca Raton, FL. 

If we are to quantify the risks that environmental pollution poses, we need an understanding of the many factors that affect the distribution of a chemical in the environment. The fugacity model of Mackay et al. (1992) incorporates these factors, one of which is bioaccumulation. Connell (1990) has written a comprehensive review of the bioaccumulation of xenobiotic compounds. 

Avoid the discharge of persistent and bioaccumulating, or persistent and highly mobile, xenobiotics into the environment, as well as chemicals whose metabolites exhibit these properties. 

Kleinow, K.M. Melancon, M.J. Lech, J.J., Biotransformation and induction Implications for toxicity, bioaccumulation, and monitoring of environmental xenobiotics in fish Environ. Health Perspect. 1987, 71, 105-119. 

In real life , humans and animals can be exposed to some toxicants both pre- and postnatally. Many organic xenobiotics have the potential to bioaccumulate within exposed individuals, possibly affecting future generations by way of genetic and epigenetic effects. However, reproductive endpoints, such as conception rates and sperm counts, are relatively insensitive, and subtle, toxicant-induced changes in reproductive efficiency can be overlooked or missed (Evans, 2007). 

Bioaccumulation The accumulation of xenobiotic substances in organisms and the food chain is important in the assessment of the harmfiilness of a substance in the environment. The accumulation of organic substances in organisms occurs often in accordance with their lipophilicity (Figure 9.29) A ow often serves as a measure of lipophilicity and as a predictive parameter for bioaccumulation in the food chain. One also speaks of biomagnification to describe progressive accumulation of xenobiotic substances in the food chain. 

A great deal can occur to a xenobiotic between its introduction to the environment and its interaction at the site of action. Many materials are altered in specific ways depending upon the particular chemical characteristics of the environment. Bioaccumulation, the increase in concentration of a chemical in tissue compared to the environment, often occurs with materials that are more soluble in lipids and organics (lipophilic) than in water (hydrophilic). Compounds are often transformed into other materials by the various metabolic systems that reduce or alter the toxicity of materials introduced to the body. This process is biotransformation. Biodegradation is the... 

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