April 27th, 2011
(Hixson) – What is Bioaccumulation?
- Bioaccumulation refers to how pollutants enter a food chain
- Biomagnification refers to the tendency of pollutants to concentrate
A Deeper Definition
- Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism.  Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost. Thus, the longer the biological half-life of the substance the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high.
- Bioaccumulation –
The biological sequestering of a substance at a higher concentration
than that at which it occurs in the surrounding environment or medium.
Also, the process whereby a substance enters organisms through the
respiratory tract, gills, epithelial tissues, dietary, or other sources.
Other Terms To Know
- Uptake, the
entrance of a chemical into an organism — by breathing, swallowing, or
absorbing it through the skin — without regard to its subsequent
storage, metabolism, and excretion by that organism.
- Storage, temporary deposit of a chemical in body tissue or in an organ.
- Biomagnification, a process that results in the accumulation of a chemical in an organism at higher levels than are found in its food. This occurs when a chemical increases in concentration as it moves up through a food chain.
- Biomagnification describes
a process that results in the accumulation of a chemical in an organism
at higher levels than are found in its food. It occurs when a chemical
becomes more and more concentrated as it moves up through a food chain
— the dietary linkages between single-celled plants and increasingly
larger animal species.
- Biomagnification in
the aquatic food chain often leads to biomagnification in terrestrial
food chains, particularly in the case of bird and wildlife populations
that feed on fish.
- Biomagnification describes
- Elimination, whether
an organism can break down or excrete a chemical. Chemicals that
dissolve in fat but not in water tend to take longer to be eliminated by
the body, and have a greater potential to accumulate.
Examples of Biomagnification
- In a classic example of biomagnification,
microorganisms in the ocean are exposed to pollutants, and the fish
which eat them also ingest these pollutants. Larger fish eat the smaller
fish, and the larger fish are eaten by seals. At every step of the way,
the concentration of the pollutant becomes ever higher, representing
the pollution passed on from dozens or hundreds of animals. When a polar bear
eats the seal, the biomagnified pollutants will build up to
unprecedented levels in the body of the polar bear, causing the polar to
get sick, pass on genetic abnormalities to its children, or die.
of the big problems with biomagnified pollutants is that it can be
difficult to identify them until they have reached the higher levels of
the food chain. In the polar bear example above, it may take decades for
the pollutants to manifest in the polar bear population, by which time
it is too late to take steps to reduce their prevalence in the
atmosphere and ocean. Scientists can determine that biomagnified
pollutants are making the polar bear sick, but they cannot take
substantial action to prevent more polar bears from getting sick, beyond
restricting the distribution of the pollutant in the hopes that it will
eventually work its way out of the food chain.
2. Biomagnification is illustrated by a study of DDT which showed that where soil levels were 10 parts per million (ppm), DDT reached a concentration of 141 ppm in earthworms and 444 ppm in robins. DDT which has a half-life of 15 years, Strontium 90 which has been shown in EPA testing results in the United States has a half-life of 28.9 years, Cesium 137 has also been found which has a half life of 30 years. Through biomagnification, the concentration of a chemical in the animal at the top of the food chain may be high enough to cause death or adverse effects on behavior, reproduction, or disease resistance and thus endanger that species, even when levels in the water, air, or soil are low.
must be concerned about these phenomena because together they mean that
even small concentrations of toxic substances in the environment can
find their way into organisms in high enough dosages to cause problems.
If a chemical is short-lived, it generally will be broken down before
it can become dangerous. However, even if short-lived chemicals are
exposed to the environment for long periods of time in heavy doses, they
too can become dangerous. Bioaccumulation is affected by the length of time between uptake and elimination of chemicals. If
the environmental concentration of the chemical increases, the amount
inside the organism will increase until it reaches a new equilibrium.
Exposure to large amounts of a chemical for a long period of time,
however, may overwhelm the equilibrium (ie, overflowing a bathtub)
potentially causing harmful effects.
The easiest way to prevent biomagnification is to lower/remove the pollutants from the environment, or remove those effected from the polluted area.
do you prevent Biomagnification if you cannot control the length of
exposure, or the amount of radiation introduced into the environment?
What will companies do to keep getting your money?
- BP covered up the actual amounts of oil being released
- TEPCO has raised released radiation estimates gradually over the course of weeks even though more accurate data was available.
Companies exaggerated the effectiveness of anti-depressants by
publishing only positive drug trials and shelving negative ones.
Knowing this are we able to trust major food suppliers to accurately report contamination in our food supply?
Biomagnification and Heavy Metals
metals are chemically stable, and therefore cannot be destroyed or
converted into a non-toxic form. (Except for the case of a radioactive
metal, which will change into a differerent chemical element when it
undergoes radioactive decay.) Problems arise when organisms are exposed
to higher concentrations than usual, which they cannot excrete rapidly
enough to prevent damage. There is limited research available in
multi-element biomagnification studies on radionuclides.
only is the media and international governments downplaying the
disaster at Fukushima, there has also been a lack of research on the
effects of the radioactive particles after they have been exposed to the
environment. In a earlier post, we showed a video of TEPCO officials
being questioned by reporters as to WHY they had to dump high
radioactive waste into the ocean. TEPCO Officials responded by stating
that they had received permission from the government, but did not have
enough information to make a public statement as to WHY they were
dumping the waste into the environment.
And its not just the radioactive waste, there is also radioactive debris…
From the Congressional Research Service:
on computer modeling of ocean currents, debris from the tsunami
produced by the Tohoku earthquake is projected to spread eastward from
Japan in the North Pacific Subtropical Gyre. In three years, the debris
plume likely will reach the U.S. West Coast, dumping debris on
California beaches and the beaches of British Columbia, Alaska, and Baja
California. Although much of the radioactive release from Fukushima
Daiichi is believed to have occurred after the tsunami, there is the
possibility that some of the tsunami debris might also be contaminated
radiation levels have exponentially increased weekly, since the initial
public statements. It was also exposed that the EPA had begun testing
for radioactive particles from Fukushima in the United States on March
11th, and by March 18th had already reported Cesium, Plutonium, and
Strontium particles on the other side of the Pacific Ocean. Some have
called this incident the biggest manmade release ever of radioactive
material into the oceans. As radiation passes over the Pacific Ocean,
it will be brought to the earth by precipitation, debris, and other
objects it comes into contact with. These dangerous particles can then
be introduced into water supply, grain and dairy products, and into the
Ken Buesseler – Marine Radiochemist and Senior Scientist at the Woods Hole Oceanographic Institution stated:
released by Japanese scientists show cesium-137 concentrations in the
waters immediately adjacent to the reactors at levels more than 1
million times higher than previously existed and 10 to 100 times higher
in the waters off Japan than values measured in the Black Sea after
Chernobyl. For the oceans, this is the largest accidental release of
radiation we have ever seen.
But what do these high values mean for ocean life and human health? What will it mean 25 years from now? read more here
How does cesium-137 and strontium-90 bioaccumulate?
The radionuclides cesium-137 and strontium-90 are both fission products with a radiological half-life of about 30 years. If released into the environment, they can both concentrate again at various steps of the food chain. The way they accumulate depends on their chemical behavior.
- Cesium-137 has chemical properties that are similar to potassium. Because the cells in plants, animals and in the human body cannot distinguish between cesium-137 and potassium, cesium-137 can be mistaken by the body to be potassium and absorbed as such. Because most potassium in the human body is found in the blood, cesium-137 can be found in all parts of the human body.
- Strontium-90, on the other hand, has chemical properties similar to that of calcium. Hence, strontium-90 concentrates in milk and bones.
Latest from Japan
day reveals more setbacks in the attempts to control the disaster at
Fukushima, and even the experts are telling us they have no idea how
long it will take to regain control. While in one hand telling the
public, “There is no immediate danger”, they also have stated they don’t
know the full risk of cumulative contamination on the global
environment and population.
April 26th, TEPCO stated the levels of cesium-134 and 137 increased
about 250-times and iodine-131 increased about 12 times compared with
the levels one month ago. TEPCO also stated the water being used to
cool the No. 3 reactor could be leaking into No. 4 as their turbine
buildings are connected. The government’s nuclear agency separately
said that water may be leaking from the No. 1 reactor container of the
crisis-hit Fukushima plant, and that remote-controlled robots are
expected to check the situation inside the reactor building.
high levels of contaminated water continues to increase, it becomes
difficult to install a cooling system and make the roadmap by mid-July
as stated by Tokyo Electric Power.
though the radiation levels at Daiishi are so high its hampering the
cooling process, all major media outlets are still reporting that there
is no risk internationally. The water levels inside of Reactor #3 rose
to 99 centimetres below the surface on 04/24/2011, which exceeds the
level that TEPCO planned to allow. The problem is there is no place to
store the radioactive waste, and every day more elements are introduced
into the environment.
Effects of Radiation Doses
- < 50 rads (< 0.5 Gy) Generally no clinical effect; subject asymptomatic.
- 50-100 rads (0.5-1.0 Gy) Mild nausea; white blood cell count (WBC) increases, then decreases.
- 100-200 rads (1-2 Gy) Nausea and vomiting; fatigue; WBC increases, then decreases.
- 200-400 rads
(2-4 Gy) 2 to 3 days of nausea and vomiting, fatigue, WBC and platelets
decreased; epilation, diarrhea, bleeding; recovery period 1-3 weeks.
- 300-500 rads (3-5 Gy) Lethal dose to 50 percent of the people exposed.
- 400-600 rads
(4-6 Gy) Severe nausea, vomiting and diarrhea, sore throat, WBC and
platelets decreased, symptoms recur, hemorrhages; recovery period brief
or absent. Death to most in < 30 days.
- 600-1,000 rads (6-10 Gy) Severe and continuing nausea, vomiting and diarrhea; death to most in 1 to 10 days.
- > 1,000 rads (> 10 Gy) Severe illness, disorientation, ataxia, burning sensation, shock; all die, most in 10 to 36 hours.
Source: Fowler, J.: Biological Effects of Radiation. In: Wilson, M. (Ed.): Textbook of Nuclear Medicine. Philadelphia: Lippincott-Raven, 1998)
Source: Lucas Whitefield Hixson