Biological accumulation and magnification are only two among a multitude of issues which the environment confronts today. The emergence of advancements in modern technology spearheaded the discovery of substances which threaten the environmental stability. Such substances include mercury, selenium, cadmium, chlorinated hydrocarbons and chemical pesticides which are contributing greatly to the industries where these substances are needed but, consequently and undeniably, have induced danger in the ecosystem and caused peril in the lives of organisms inhabiting therein.
Chiras (1994) defines biological accumulation as a process which refers to the build-up of chemicals within body tissues and organs. Nebel& Wright (1996) assert that the chemicals which tend to consolidate in an organism are particularly hazardous and include heavy metals and non-biodegradable synthetic organics. This is a phenomenon which involves the mounting up of chemical substances absorbed by the body of an organism through small, seemingly harmless amounts which may reach toxic levels if these are being received by the body contentiously over a long period of time.
Though the body absorbs the harmful substances in smaller concentrations, still this poses a danger to the organism because the harmful substances are continually accumulating within the body. Furthermore, there are no body mechanisms adapted to excrete these substances or metabolize them further. Thus, toxic substances are trapped within the body organs and held by the enzymes and lipids present in the body (Nebel & Wright, 1996). The body of an organism can be compared to a filter. Particles which are large enough to pass through the filter holes tend to aggregate on the filter because there are no means by which the impurities can ingress the filter pores. Same principle applies in the accumulation of toxic substances in the body.
As Nebel & Wright (1996) explain, heavy metals are dissolved in water but they are being separated in the solution if they have been bound in the body enzymes. The water, which is now considered waste, passes through the urinary system but the heavy metals are trapped in the enzymes and lipids. As it ahs been stated, these toxic substances cannot be excreted. As a result, these toxic substances will continually pile up through time until concentrations are high enough to prompt complications and disorders within the organism’s body (Nebel & Wright, 1996).
Bioaccumulation occurs within an organism but when the circumstance has already created a multiplying effect among the organisms involved in a particular food chain, a phenomenon known as biological magnification will soon take place
Biological magnification, as Raven, Berg & Johnson (1993) posit, is the tendency wherein “organisms at higher levels on food webs tend to have greater concentrations of harmful substances stored in their bodies than those on lower food webs” (p. 503). The multiplying effect of bioaccumulation, which Nebel & Wright (1996) found out, occurs when a certain organism in a food chain has fed on another organism which has accumulated the contamination of toxic substances in its food. The succeeding organism in the food chain will tend to acquire a large concentration of toxins because it fed on an organism which is more contaminated by toxic substances as it has been before. As next organisms in the food chain tend to fulfill the process, larger amounts of synthetic organics will be stored in them. To simplify, “harmful substances are concentrated as it passed up on food chains, so that the higher an organism is on a food chain, the higher the concentration of the substance it contains” (Bothen & Keller, 1995, p. 208).
To illustrate the process of biomagnification, Raven, Berg & Johnson (1993) gave a hypothetical food chain:
Plant -> Insect -> Frog -> Hawk
Let it be presumed that a plant contains mercury content due to contamination. Each insect that regularly feeds on the plant grazes approximately ten leaves. A frog near the vicinity eats at least ten of those insects. The hawk, considered as a bird of prey, feeds on the frogs and consumes ate least ten of those. Given this example, it can be stated that the hawk contains the largest amounts of mercury among the participants in the food chain. Aside form the fact that the hawk is at the topmost level of the food chain, the mercury content has been handed from the plant down to the hawk. The hawk eating a sheer number of mercury-dosed frogs indeed depicts a magnification of the toxic substance within the body of the aforementioned carnivore. Bothen & Keller (1993) added that not only hawks but also all top carnivores, including humans have the greatest tendency to be a victim of biomagnification.
The technological advancements which led to the development of chemical pesticides and other toxic substances such as dichlorodiphenyltrichloroethane (DDT) and chlorinated hydrocarbons, including aldrin and dieldrin, have been p[perceived as the cause of severe predicaments created by biomagnifications. The rise of modern agricultural sciences paved the way for the manufacture of broad-spectrum pesticides which adversely affect the environment on a large scale. All of these circumstances have brought the biomagnifications problem into a higher level.
For instance, chemical pesticides tend to move through the soil, water and air. Sometimes, it reaches long distances, far beyond the particular area where the pesticide has been applied. To make this episode worse, pesticides are extremely stable that they take many years to be broken down. Even natural decomposers have not adapted ways on how to disintegrate them (Raven, Berg & Johnson, 1993). Thus, this poses a greater threat to the fishes, for example, which can be affected by pesticides that were applied to agricultural lands and then washed into rivers and streams when it rained (Raven, Berg & Johnson, 1993).
A. The Minamata Tragedy
As it has been reiterated, biomagnification brings negative effects in the environment, more especially to the organisms which inhabit therein.
A classic example of such case is the episodic tragedy which occurred at the small fishing village of Minamata, Japan on the early 1970s. A disease, which later on was named to the village itself, has infested the entire town and unveiled its reverse outcomes due to the potential of biomagnifications of mercury and other heavy metals (Nebel & Wright, 1996). A chemical company dumps mercury-contained wastes at the river where the Minamata villagers fish. The wastes have severely contaminated the river, more especially the fishes living in the water.
The drastic decline in the population of cats at the village has become observable and conspicuous. For the cats in Minamata, Japan “began to show spastic movements, followed by partial paralysis, coma and death (Nebel & Wright, 1996, p.350). This incident was put into oblivion but later on, such symptoms have also manifested to some of the villagers. Health disorders and mental defects have immediately come into this episodic scenery. Health experts have asserted the cause of such odd behavior is acute mercury poisoning (Nebel & Wright, 1996).
The Minamata cats became the pioneer victims of the poisoning because they primarily feed on the dead remains of the fishes. The villagers have also been affected by such circumstance because of their fish consumption. As a result, 50 persons had died and 150 persons have been afflicted by bone and nerve damage (Nebel & Wright, 1996).
B. The DDT Dilemma
In the1950s and 1960s, the populations of bird species which feed at the top of food chains have enormously decreased. The reproduction of the birds of prey such as eagles, pelicans, ostriches and falcons has been thoroughly affected by the substance called dichlorodiphenyltrichloroethane (DDT). This toxic substance has endangered the lives not only of bird species but also of other carnivores (Raven, Berg & Johnson, 1993). Bothen & Keller (1995) has asserted that DDT affects the ability of the birds to produce eggs. For truly, according to the US Fish and Wildlife National research Center (as cited in Nebel & Wright, 1996), the problem was reproductive failure. Eggs became fragile and brittle, and premature hatching became a common scene. It was soon discovered that the eggs contain large concentrations of DDT which intervenes calcium metabolism in the eggs.
This predicament was rooted in the contamination of the bird species by the DDT which they have acquired on feeding with other organisms which also are contaminated by the toxic substance (Bothen & Keller, 1995).
Laws and regulations have been passed owing to the problems induced by the biomagnification process.
The toxic substance DDT was already banned in most affluent countries, more particularly in the United States on 1971. After the DDT usage was prohibited, the recovery of reproductive ability of some bird species which have been affected by the DDT became rapid. Species such as the brown pelican which live at the Californian coast and the bald eagle have become abundant again (Bothen & Keller, 1995).
In the United States, policies regulating the use of chemicals, more particularly pesticides, on farms, chemical establishments, and around the home have been ratified by the Federal Government. These regulations have been brought into the limelight because there has been an urgent necessity to protect public health and the environment, more especially.
On 1947, the passage of the Federal, Insecticide, Fungicide and Rodenticide Act (FIFRA) has commenced the passage of the series of laws mandating the regulation of pesticide use as ell as the responsible utilization of such chemicals. These laws were adapted primarily to address concerns regarding the manufacturing of “substandard and fraudulent” pesticides and insecticides which reversely affect the environment in an enormous scale. More especially, the law “focused public attention on the risks of pesticides such as DDT to human health and the environment, bringing about major changes in the use of pesticides” (Southern Region Pesticide Impact Assessment Program, 1996).
In the Philippines, the Presidential Decree No. 144 (Creating The Fertilizer And Pesticide Authority And Abolishing The Fertilizer Industry Authority) is a relatively similar mandate which mirrors the principles of the American FIFRA, for the decree asserts that “improper pesticide usage presents serious risks to users, handlers, and the public in general because of the inherent toxicity of these compounds which are, moreover, potential environmental contaminants” (Chan Robles Virtual Law Library, n.d.). Also a particular section of the decree offers a condition which restricts or bans “the use of any pesticide or the formulation of certain pesticides in specific areas or during certain periods upon evidence that the pesticide is an imminent hazard, has caused, or is causing widespread serious damage to crops, fish or livestock, or to public health and the environment.” (Chan Robles Virtual Law Library, n.d.).
The policies and laws which are mentioned above seek to diminish the use of chemicals which induce harm to the environment. Truly, toxic chemicals tremendously affect the flow of ecosystem for these put the lives of the living organisms in danger. Biological accumulation and magnification are present environmental issues which, indeed, must be resolved as soon as possible.
- Bothen, P. & Keller, E. (1995). Environmental Science: Earth as Living Planet. USA: John Wiley & Sons, Inc.
- Chan Robles Virtual Law Library (n.d.). Presidential Decree No. 144 (CREATING THE FERTILIZER AND PESTICIDE AUTHORITY AND ABOLISHING THE FERTILIZER INDUSTRY AUTHORITY). Retrieved 22 September 2011, from http://www.chanrobles.com/presidentialdecrees/presidentialdecreeno1144.html
- Chiras, D. (1994). Environmental Science. Actions for Sustainable Development. USA: Bnjamin/Cummings Publishing Company, Inc.
- Nebel, B. & Wright, R. (1995). Environmental Science: The Way the World Works. USA: Prentice Hall International, Inc.
- Raven, P., Berg, L. & Johnson, G. (1993). Environment. USA: SaundersCollege Publishing.
- Southern Region Pesticide Impact Assessment Program (1996). Federal Pesticide Laws and Regulations. Retrieved 21 September 2011, from ipm.ncsu.edu/safety/factsheets/laws.pdf