Excretion bioaccumulation

Most marine mammals are exposed to relatively high concentrations of those contaminants considered to be persistent (do not breakdown readily in the environment), bioaccumulative (are not readily metabolized and excreted by biota in aquatic food webs), and (immuno)toxic. Candidates in this category include various congeners of... 

Another entry point for accumulation of organic in animal tissue and animal food products is direct ingestion of contaminated soil by grazing animals [44]. The compounds of main concern are the halogenated aromatics, including PCBs, organochlorine pesticides, PCDDs and PCDFs, which are resistant to metabolization and tend to accumulate in animal fat. The bioaccumulation factor (the ratio of the concentration of animal tissue or produce to the concentration in the diet) can be as high as 5-6 [43]. Compounds such as PAHs and phthalate esters are readily metabolised and excreted by the animals and thus do not accumulate in animal tissue or products. 

In a static model ecosystem, several amino derivatives of fenitrothion, probably derived from the soil metabolism, were demonstrated in carp tissues, together with the nitro-containing compounds. The concentration of fenitrothion in carp, snails, daphnids and algae decreased with time, although its bioaccumulation ratio relative to the concentration in water tended to increase gradually in snails, daphnids and algae, presumably due to lower metabolic activity and/or slow excretion. 

The rapid degradation of molinate and conversion to more polar metabolites which are excreted into water serves to explain the extremely low bioaccumulation potential of this herbicide in fish. 

Because PAHs are nonpolar compounds, they are hydrophobic and, hence, highly retained in the fatty tissues of organisms. This is most unfortunate given their high toxicity, which in addition to cancer, has been shown to include reproductive feilures and impairments to immune systems. Fish and mammals tend to metabolize and excrete PAHs feirly rapidly, so these compounds are less prone to bioaccumulation or biomagnification... 

Metabolism/Excretion- In healthy subjects, the half-life of pramlintide is approximately 48 minutes. Pramlintide is metabolized primarily by the kidneys. Des-lys pramlintide (2-37 pramlintide), the primary metabolite, has a similar half-life and is biologically active both in vitro and in vivo in rats. AUC values are relatively constant with repeat dosing, indicating no bioaccumulation. 

If the intake of a long-lasting contaminant by an organism exceeds the latter s ability to metabolize or excrete the substance, the chemical accumulates within the tissues of the organism. This is called bioaccumulation. 

James, M., Moore, M., Plotzke, K., Segner, H., Schultz, I., Thomas, K., Vasiluk, L. and Weisbrod, A. (2007) Use of in vitro Absorption, Distribution, Metabolism, and Excretion (ADME) data in bioaccumulation assessments for fish. Human Ecol Risk Assess, 13, 1164-1191. 

Bioaccumulate Refers to a biological organism absorbing and retaining more of a toxic substance than it excretes. 

Thus, overall, the bioaccumulation of PCBs is a function of the uptake of PCBs from water and food, and the losses due to metabolism, excretion, and growth dilution all are a function of time. A general model for estimating the concentration of PCBs (Cflsh) in fish is ... 

Cullen, W.R., Harrison, L.G., Li, H. and Hewitt, G. (1994) Bioaccumulation and excretion of arsenic compounds by a marine unicellular alga, Polyphsa peniculus. Appl. Otganomet. Chem., 8, 313—324. 

Bioaccumulants Substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted. (See Biological magnification.)... 

As mentioned previously and shown in Fig. 6.8, movement of a chemical in a system containing plants or animals may involve exchange with the air, soil, and water phases. Bioaccumulation results when the plant or animal uptakes the contaminant. In plants, the contaminant may be, in turn, released to the air by means of volatilization or to the soil with subsequent accumulation by phytostabilization, adsorption, and sedimentation or transport to the aqueous phase by advective, diffusive, or dispersive processes. Excretion of the contaminant or a metabolite from animals may also be received by any compartment. 

Animals. Widely distributed and quickly eliminated no bioaccumulation. The major routes of excretion were feces and urine. Thirty two different metabolites were identified... 

Animals. In mammals, following oral administration, glyphosate is very rapidly excreted unchanged and does not bioaccumulate... 

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