of the consumer. Since every organism loses water to the environment, as the water is lost the pollutant would leave as well. Alas, fat simply does not leave the
body Marietta College, 2006.
B. Chemical can be Occurred Biomagnification
In a review of a large number of studies, Suedel et al 1994 concluded that although biomagnification is probably more limited in occurrence than
previously thought, there is good evidence that DDT
, DDE
, PCBs
, toxaphene
, and the organic forms of
mercury and
arsenic do biomagnify in nature. For other
contaminants, bioconcentration and bioaccumulation account for their high concentrations in organism tissues. More recently, Gray 2002 reached a similar
conclusion. However, even this study was criticized by Fisk et al., 2003 for ignoring many relevant studies. Such criticisms are spurring researchers to study
carefully all pathways, and Croteau et al. 2005 recently added Cadmium to the list of biomagnifying metals.
http:en.wikipedia.orgwiki .
There are two main groups of substances that biomagnify. Both are lipophilic and not easily degraded. Novel organic substances are not easily
degraded because organisms lack previous exposure and have thus not evolved specific detoxification and excretion mechanisms, as there has been no selection
pressure from them. These substances are consequently known as Persistent Organic Pollutants or POPs. Persistent organic pollutants POPs are those
chemicals that are not materially broken down over a reasonable period of time, usually measured in decades or more. The POPs of most concern are those that
build up in the environment or are bioaccumulated andor biomagnified in the food chain. The realization and importance of persistent environmental chemicals
was first identified in the early 1960s with the publication of Rachel Carsons seminal work, Silent Spring. Carson wrote of the buildup of pesticides in birds
and hypothesized that this came from direct and indirect food chain exposure. The magnitude of effect from Carsons work can be appreciated when one
considers the breadth of environmental health sciences today and the international environmental regulations that have been promulgated.
The chemical characteristics of POPs are relatively similar. Many are polyhalogenated aromatic hydrocarbons PHAHs, or other polycyclic aromatic
hydrocarbons PAHs that are very slowly metabolized or otherwise degraded. The chemicals are lipid soluble; hence they are stored in the fatty tissue of all
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animals, and they build up in the food chain. Some classic examples of POPs are the pesticides DDT, Dieldrin, Aldrin, Heptachlor, Mirex, and Kepone. Another
group of POPs are the chlorodibenzodioxins, dibenzofurans, and some PCBs. The pesticides were widely used for several years but eventually discontinued for
toxicological and ecological reasons. Because of their lipid solubility, the chlorinated compounds are retained and accumulated in the lipids of insects and
other invertebrates that are part of the food chain of higher-order predators, and they can eventually end up in the diets of humans and feed animals. Several of
these compounds can be sequestered in soil and sediment, such as the PCBs in the Hudson River bottom sediment, where they can exist for decades.
The health effects of these chemicals, as neat compounds, have been very well studied. However, low-dose, lifetime exposure studies are lacking.
Many of the organochlorine pesticides cited above are carcinogenic, teratogenic, and neurotoxic. The dioxins and benzofurans are highly toxic and are extremely
persistent in the human body as well as the environment. Several of the POPs, including DDT and its metabolites, PCBs, dioxins, and some chlorobenzene, can
be detected in human body fat and serum years after any known exposures. Lindane hexachlorocyclohexane, which was used for the treatment of body lice
and as a broad-spectrum insecticide, resulted in very high tissue levels, and in many cases caused acute deaths when used improperly. Lindane and some of
its isomers have been identified in market-basket surveys and in human fat samples.
Novel organic substances are DDT, PCBs, and Toxaphene and Inorganic substances are Mercury, Arsenic, and Cadmium. DDT is a colorless contact
insecticide, C
14
H
9
Cl
5
, toxic to humans and animals when swallowed or absorbed through the skin. It has been banned in the United States for most uses since
1972.A colorless insecticide that kills on contact. It is poisonous to humans and animals when swallowed or absorbed through the skin. DDT is an abbreviation
for dichlorodiphenyltrichloroethane. Although DDT, when it was first invented, was considered a great advance in protecting crops from insect damage and in
combating diseases spread by insects, recent discoveries have led to its ban in many countries. Residue from DDT has been shown to remain in the ecosystem
and the food chain long after its original use, causing harm and even death to animals considered harmless or useful to man
http:en.wikipedia.orgwikiTalk:Biomagnification.
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According to Marietta College 2006, not only DDT is toxin to biomagnify, but also all of the following have the potential to biomagnify Table 1.
Table 1. List of Chemical which has Potential to Biomagnify.
Substance Use and Problems
Links
PCBs polychlorinated biphenyls
•
insulators in transformers
•
plasticizer
•
fire retardant
•
biomagnifies
•
impairs reproduction
•
widespread in aquatic systems
•
as airborne contaminants
•
in sediments
•
in the Mississippi River
PAHs polynuclear aromatic
hydrocarbons
•
component of petroleum products
•
carcinogenic Heavy metals:
•
mercury
•
copper
•
cadmium
•
chromium
•
lead
•
nickel
•
zinc
•
tin TBT or tributyltin
•
mercury from gold mining
•
many from metal processing
•
may affect nervous system
•
may affect reproduction
•
from an interesting student project
•
heavy metals in the Mississippi River
- great source
cyanide
•
used in leaching gold
•
used in fishing
•
toxic
•
effects on coral reefs
•
health information
•
proposed gold mine
and its effects
•
report of a spill
of cyanide selenium
•
concentrated by farming desert soils
•
reproductive failures
•
toxic
•
selenium at a wildlife
refuge in Wyoming
Source: http:www.marietta.edu~biol1022bioma95.html
C. Properties of Biomagnification Chemicals
