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Thursday, June 7, 2012

Bioaccumulation and its effects;

Bio-accumulation and environmental hazards;

What are the ecosystem effects of bio-accumulation? 

 What are bioaccumulation issues?

Bio-accumulation refers to the accumulation of substances, like pesticides or other organic chemicals in an organism; it is the biological sequestering of a substance at a higher concentration than that of usual. Bioaccumulation describes also the way pollutants enter an ecosystem. Many human activities, such as pesticides use, and coal burning introduce these harmful substances like DDT, methyl mercury, and other organic chemicals into the environment. These substances are known as persistent bioaccumulative toxic substances.

How bioaccumulation occurs

Bioaccumulation occurs when the persistent toxic substances enter an organism through breathing, ingestion or skin contact more quickly than the substances can leave the organism. The organism has in this state a higher concentration of the substances than the surrounding environment.

Persistence determination

Persistence is measured by determining the lack of degradability of a substance from a form that is biologically available and active to a form that is less available. This applies to synthetic organic substances. Inorganic metals and metal compounds tend to be in forms that are not bioavailable, but under specific conditions, inorganic metals and metal compounds would be transformed into a bioavailable form. The criteria to classifying inorganic metals and metal compounds are their capacity to transform into bioavailable form.


The primary determining factor of hazard for inorganic metals and metal compounds is the toxicity, which requires consideration of dose because the fundamental tenet of toxicology is the dose that makes the poison. However it is demonstrated that in different media, metal ions compete with different types and forms of organic matter to reduce the total amount of metals present in bioavailable form. Toxicity of the bioavailable fraction is the most appropriate method for categorizing and ranking hazard of inorganic metals and metal compounds.

Bioaccumulation and environmental hazards:  

The potential of bioaccumulation can lead to three main environmental hazards, thus bioaccumulation its self, bioconcentration, and biomagnifications, which corresponds to effects at the individual, population, and community levels. Bioaccumulation represents a potential hazard for long term or retarded effects on the individual suffering the accumulation. The chemical can reach critical body burden in target organs when exposed for long periods to low doses. When the chemical is accumulated in a particular tissue such as fat, high blood concentration can be reached when that fat tissues are metabolized during starvation, pregnancy or other stressing activities.


Bioconcentration is a process indicating that concentration in an organ is higher than the concentration in the surrounding such as water or air. It may not represent a hazard for the individuals suffering the accumulation, but for those populations which use these individuals as source of food. Blood alcohol content or blood alcohol concentration is the metric of alcohol in blood.


Biomagnification or biological magnification is the increase in concentration of a substance that occurs in food chain. When the persistent bioaccumulation toxic substance has accumulated in one part of an ecosystem, biomagnification occurs as that substance becomes concentrated from one link in the food chain.

Ecological concept

Suggests that at the community level, the bioaccumulation resulting from the consumption of contaminated food can be repeated several times through the food chain. Persistence is obviously related to the compartments of concern. Toxicity is however related to the ecological receptors expected to be at risk and requires specific consideration. A pollutant biomagnification can have a major impact on the ecosystem if the pollutant characterizes as long lived, mobile, biologically active, and dissolves in fats.

Ecosystem Effects

Bioaccumulated contaminants can affect populations and threaten biodiversity in insidious, sub lethal ways. The effects of bioaccumulation are not limited to local ecosystems. In fact the persistent bioaccumulation toxic substances make their way through the global environment with startling ease. High volatile persistent bioaccumulation toxic substances are carried by the wind, often over very long distances and then disposed in a new ecosystem, via either precipitation or settling particulate matter. After accumulating in that ecosystem, they evaporate and travel again through the atmosphere until the temperature drops and they condense and return to the earth. This cycle continues until there is not enough geothermal energy to go through another evaporation cycle. At this point the persistent bioaccumulation toxic substances may have accumulated in numerous ecosystems along the way. Biomagnified contaminants inevitably lead to decrease birth rates, increase death rates and ultimately declining populations.
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