A subject this author wrote her thesis on inspired by an article I wrote on this subject matter.
ENVIRONMENTAL ESTROGEN ENDOCRINE DISRUPTORS
AND THEIR EFFECT ON WILDLIFE
written by:
Kathryn Guardiola
Biology 4950
Advisor: Dr. Smith
Senior Seminar Coordinator: Dr. Smith
July 3, 2006
Table of Contents
Table of Figures *Outline *Abstract *Background of EDCs and their environmental effects *Historical background *The environment remains in danger *Controversy surrounding EDCs *EDCs have a variety of sources, chemical structures and effects on organisms *Sources of EDCs *Bioaccumulation *Endocrine Disruption spans the food web *EDCs are discovered in higher organisms *EDCs omnipresent in environment *EDCs are found in various organisms throughout the world, they cause many detrimental effects and they must be stopped *EDCs span the globe and the food web *EDCs have affected countless organisms *EDCs require further investigation *A call to action *References *Table of FiguresFigure 1: Selected Steroidal Hormones *Figure 2: Pesticides determined to cause endocrine disruption *Figure 3: Selected Industrial chemicals and their structure *Figure 4: An example of a Marine Antarctic food web *****Figures not included*******
OutlineThesis statement: Endocrine disrupting chemicals are being unremittingly introduced into nature via countless sources, and these substances are having profound, detrimental effects of a variety of wildlife organisms. Unless immediate action is taken, EDCs pose a threat to the future existence of healthy ecosystems.
I.EDCs have a history of controversy and environmental effects.
A.EDCs have a long historical background.
1.DDT, a known EDC has been widely used in the past.
2.DDT was discovered to cause harm to the environment.
a.Rachel Carson exposed effects of DDT in her book "Silent Spring."
b.DDT was banned by the EPA in 1972.
B.The environment remains in danger.
1.DDT breaks down slowly and has harmful by-products.
2.Other EDCs are being introduced to the environment at profound rates.
3.There are various sources of EDCs both natural and synthetic.
4.EDCs interfere with the endocrine system of the body.
a.EDCs interfere with hormones in the body.
b.EDCs interfere with development, growth and reproduction.
C.There is
controversty surrounding EDCs.
1.The EPA named EDCs a top research priority.
a. The initiative came after the EPA was threatened by lawsuit.
b.The paper industry attempted to keep negative effects of dioxin hidden.
2.The commercial value of EDCs keeps them hotly debated.
a.Many popular products are sources of endocrine disruptors.
b.Many industries desire to keep products on market regardless of environmental implications.
II.
EDCs have a variety of sources, chemical structures and effects on organisms.
A.There are a number of sources
of EDCs (Hohenblum, Gans, Moche, and others 2004).
1.Natural and synthetic steroidal hormones are a source of EDCs.
a.Estrogens produced by the body are a source of EDCs.
b.Synthetic estrogens used in pharmaceuticals are a source of EDCs.
2.Anthropogenic industrial chemicals are a source of EDCs.
a.Pesticides are a source of EDCs.
b.Polychlorinated biphenyls (PCBs) are a source of EDCs.
c.Dioxins are a source of EDCs.
d.Alkylphenols are a source of EDCs
e.Bishpenol A is a source of EDCs.
B.There is a basic common
chemical structure of EDCs.
1.EDCs usually have at least one aromatic ring in their chemical structure.
2.Many EDCs have chlorine atoms attached.
3.The close resemblance to natural estrogens allows synthetic compounds to bind receptors with ease.
4.Mimicking, blocking or disrupting may still be achieved by EDCs regardless of molecular structure.
C.EDCs move up the food chain during
bioaccumulation.
1.It is believed that EDCs enter the environment at the base of the food web.
a.EDCs have been discovered in sea ice algae, krill, and plankton.
b.The base of the food web is where bioaccumulation begins.
2.EDCs are lipophilic, causing them to absorb and magnify in creatures with
higher body fat (Chiuchiolo, Dickhut, Cochran, and others 2004).
3.Experimenters found that lipid content of several analyzed tissues was the
determining factor in the accumulation of EDCs (Hoekstra, O’Hara, Backus, and
others 2005).
4.Bioaccumulation was reiterated by a study on lobsters (Walker, Bush, Puritz,
and others 2005).
D.
Endocrine Disruption spans the food web.
1.EDCs are found in organisms ranging from the base of the food chain up to the
highest predators.
2.Many lower organisms are being negatively affected by EDCs.
a.Crustaceans are being affected by EDCs (Walker, Bush, Puritz, and
others 2005).
b.Echinoderms (invertebrates) are being affected by EDCs (Roepke,
Snyder, and Cherr 2005).
c.Fish are being affected by EDCs. (Toft and Guillette 2005), (Elango,
Shepherd, and Chen 2006), (Zha, Wang, and Schlenk 2006).
d.Amphibians are being affected by EDCs (Bogi, Schwaiger, Ferling, and
others 2003)
e.Reptiles are being affected by EDCs (Gunderson and Bermudez and
others 2004)
E.
EDCs are discovered in higher organisms1.EDCs have been found in marine mammals.
a.EDCs have been discovered in polar bears (Dietz, Riget, Sonne, and
others 2004), (Verreault, Muir, Norstrom, and others 2005).
b.EDCs have been found in Arctic beluga whales (Stern, Macdonald,
Armstrong and others 2005).
c.EDCs have been found in dolphins (Fossi, Marsili, Lauriano, and others
2004), (Marsili, D’Agostino, Bucalossi, and others 2004).
F.
EDCs omnipresent in environment1.An encompasing study found EDCs in dozens of different species from Alaska
(Hoekstra, O’Hara, Backus, and others 2005).
2. An encompasing study found EDCs in dozens of different species from
Greenland (Vorkamp, Riget, Glasius, and others 2004).
III.EDCs are found in various organisms throughout the world, they cause many
detrimental effects, and they must be stopped.
A.
EDCs span the globe and the food web.
1.EDCs are found in every corner of the globe.
2.EDCs are found in organisms of every hierarchical status.
B.
EDCs have affected countless organisms.
1.The negative effects of EDCs have been seen in many organisms.
2.Negative effects of EDCs have been observed in crustaceans, echinoderms, fish,
amphibians and reptiles.
C.
EDCs require further investigation.
1.More research is needed to find effects EDCs are having on higher organsims.
2.Several researchers mentioned the dire need for further investigation.
D.The author proposes a call to action.
1.The author suggests temporary restrictions on suspected EDCs.
2.The author suggests ceasing use of products suspected to be EDCs.
3.The author suggests writing letters to government officials.
4.The author suggests doing one's best to get the word out on EDCs.
AbstractEnvironmental estrogen endocrine disruptors (EDCs) are both natural and synthetic compounds that interfere with the homeostatic bodily functions of countless organisms. Affecting creatures throughout the entire span of the food web, these substances have been found to interfere with embryonic development, induce hermaphroditic characteristics, cause hormonal imbalances and more. The compounds are lipophilic, giving them a tendency to magnify as they move up the food chain through the process of bioaccumulation. Many EDCs have high commercial value, bringing controversy to the subject and opposition to their restriction or ban. The investigator aims to inform readers and of the environmental dangers associated with EDCs, while acting as an advocate for change. Unless immediate action is taken, EDCs pose a threat to the future existence of healthy wildlife organisms. The investigator proposes initiatives to help put a stop to the problem.
ENVIRONMENTAL ESTROGEN ENDOCRINE DISRUPTORS
AND THEIR EFFECT ON WILDLIFE
Background of EDCs and their environmental effectsHistorical backgroundIn 1948, Paul Muller received the Nobel Prize in medicine after introducing the world to the insecticide abilities of the compound dichloro-diphenyl-trichlorethane (DDT). Soon after, the compound was used widely and carelessly to curb problems caused by insects including insect typhus, malaria and lice, not to mention it served as a solution to preventing too many pesky mosquito bites and the like. DDT was used worldwide, and at times was even dusted over entire cities. During the 1950s, estrogenic properties of DDT were discovered, and the drug was found to disrupt the sexual development of roosters. However, it was not until after Rachel Carson’s famous book "Silent Spring" was published that the world started to take notice. DDT was found to be estrogenic in mammals and birds, to cause eggshell thinning, and other health problems in animals. The pesticide was banned by the Environmental Protection Agency (EPA) in 1972, and has been ever since.
The environment remains in dangerAlthough DDT may have been restricted, the environment and the animals that were affected are still in danger. DDT has a lengthy degradation pathway, with a biological half-life of eight years, so its breakdown products are still persistent in the environment. Also, compounds that have become known as environmental endocrine disruptors (EDCs) are being unremittingly introduced into nature via countless sources, and these substances are having profound, detrimental effects on a variety of wildlife organisms. Detergents, polychlorinated biphenyls (PCBs), dioxins, pharmaceuticals, plastics and many more chemicals have been named as sources of environmental estrogen. These endocrine disruptors act by interfering with messages communicated by the body’s endocrine system. The endocrine system consists of a series of ductless glands including the thyroid, pituitary, adrenal, ovaries, testes, and others, along with their associated hormones, or chemical signals that regulate certain bodily functions. Sexual development, metabolism, growth and reproduction are all partially maintained through the endocrine system.
EDCs affect the endocrine system in a few different ways. The chemicals can act as estrogen mimics, in which they bind to the body’s estrogen receptors, causing unnatural bodily reactions in organisms. The compounds may also act as anti-estrogens, in which case the chemicals prevent the binding of estrogen to its receptor. It is also possible for EDCs to interfere with the synthesis, functionality, or degradation of hormones or hormone receptors. Endocrine disruptors pose a threat to the well being of all kinds of creatures from algae, krill, and crustaceans to alligators, dolphins and polar bears. Unless immediate action is taken, EDCs pose a threat to the future existence of healthy wildlife organisms.
Controversy surrounding EDCsThe EPA recently named endocrine disruptors as one of its top 6 research priorities and it began the Endocrine Disruptors Research Initiative. However, this seemingly responsible call to action has not always been the position held by the EPA. In 1986, the EPA agreed to demands from the paper industry to keep the results of its National Dioxin Survey from the public. (Dioxin is a by-product of several industrial processes including pulp and paper bleaching.) Eventually, the EPA was threatened with a lawsuit, and agreed to release the results, which found that dioxins cause damage to the immune, nervous, endocrine and reproductive systems at levels found in the general public. The topic of EDCs continues to remain quite controversial due to the fact that most EDCs have high commercial value. Birth control pills, several types of detergents, packing materials, plastic coatings, adhesives and many other popular products are sources of EDCs. Thousands of businesses would be affected by the regulation or banning of these chemicals, so one can imagine the desire many industries have to keep these products on the market regardless of the consequences.
EDCs have a variety of sources, chemical structures and effects on organismsSources of EDCsThe sources of EDCs have been confirmed through numerous studies. They are usually separated into two groups. The first group consists of both natural and synthetic steroidal hormones, which can be seen, in figure 1.
Figure 1:Selected Steroidal HormonesCompound
Structure
17-beta estradiol
17-alpha estradiol
Estriol
Estrone
17-alpha ethinyl estradiol
The main compounds here include the three natural estrogens produced by the body, namely, estradiol, estriol, and estrone, as well as the synthetic estrogen, 17-alpha ethinyl estradiol, the agent found in common pharmaceutical contraceptives. 17-beta estradiol is the major estrogen present in both male and female organisms, and 17-alpha estradiol, a metabolite of 17-beta estradiol, is found naturally in cattle and in some pharmaceuticals. Estriol, another member of this group is produced by the fetus and can cause developmental problems if found at low levels during pregnancy. Next is estrone, an estrogenic hormone originating from the gonads or the adrenal cortex.
Adapted from Table 1 in Hohenblum, Gans, Moche and others (2004).
Estrone in naturally occurring, but it can be used as the primary estrogenic component in various pharmaceutical preparations. These hormones are released into nature through the excretion of feces and urine of both humans and other organisms. Pharmaceutical contraceptives play a major role in allowing steroidal hormones to reach the environment because the body does not absorb the majority of the estrogen found in the drugs. The excess estrogen is flushed down the drain and introduced to the environment through delicate aquatic ecosystems (Hohenblum, Gans, Moche, and others 2004).
The second group of endocrine disruptors is the anthropogenic industrial chemicals, which include pesticides, detergents, plastics, dioxins, styrene and more. The EPA developed a program in 1996 to test compounds for endocrine disrupting properties. This program, known as the Endocrine Disruptor Screening Program (EDSP) is currently still underway, so clear categories have yet to be set up. However, many studies, including several that will be discussed here have shown the disruptive properties of several groups of industrial chemicals. These compounds encompass a very broad range of consumer products and many of them have important applications to modern life. The pesticides include dieldrin, lindane, mirex, heptachlore, and DDT, which is now banned but is still being found in wildlife, as well as many others. Some of these pesticides have been presented in Figure 2.
Figure 2: Pesticides determined to cause endocrine disruptionAdapted from http://www.nyu.edu/pages/mathmol/library.edu
Next among the industrial chemicals are the polychlorinated biphenyls, or PCBs, which were used in lubricants, capacitors and transformer fluids until they were banned in the 1970s. PCBs are very stable chemicals, and therefore cannot be easily degraded. This property is demonstrated by the fact that PCBs are continuing to be found in the environment regardless of the fact their use has been banned for over 30 years. The basic structure of a PCB molecule can be seen in Figure 3.
Dioxins, the next group of compounds, are considered to be some of the most toxic chemicals known to science. The EPA has identified dioxins as a serious health threat and the compounds have been linked to various health problems including cancer. Dioxins are formed as a by-product during paper manufacture, incineration, and water treatment. The structure of the molecule is depicted in Figure 3. Another group of industrial chemicals are the detergents and epoxy resins, chemically known as alkylphenols. These chemicals are used at a rate exceeding one million pounds annually in the United States alone. Products formed with alkylphenols include spermicides, wool washing detergents, car washing detergents and different types of paints. Plastics, some epoxy resins and coatings, adhesives, paints, electronic equipment, automobile parts and sports equipment are just some of the products made using the industrial chemical known as bisphenol A, or BPA. The compound is used globally, and is currently one of the most extensively tested materials being used. The structure of alkylphenols and bisphenol A can be seen in figure 3.
Figure 3: Selected Industrial chemicals and their structureCompound
Chemical Structure
PCB
Dioxin
Alkylphenol
Bisphenol A
Implications of EDC Chemical Structure As one can see in figures 1, 2, and 3, molecules that act as endocrine disruptors usually have at least one aromatic ring. Notice in figure 1 how closely the synthetic estrogen matches the naturally occurring estrogens, allowing the molecule to bind to estrogen receptors with ease. Many of the structures have chlorine atoms attached, especially the pesticides. The structure of endocrine disruptors in many cases allows the substances to mimic hormones and bind to receptors improperly. However, the mimicking, blocking or overall disrupting Adapted from http://www.nyu.edu/pages/mathmol/library.edu of the endocrine system can still be achieved by these chemicals regardless of their shape.
BioaccumulationEDCs move their way up the food chain through a process known as bioaccumulation. A recent study on the base of Antarctic marine food web discovered the presence of various chemicals in sea ice algae, water column plankton, and both juvenile and adult krill sampled from the western region of the continent. It is believed that these food sources provide the avenue through which EDCs enter the food web. Here, at the base of the web (See Figure 4) is where the bioaccumulation begins.
Figure 4: An example of a Marine Antarctic food webAvailable from http://www.landcareresearch.co.nz/research/biodiversity/penguins/food_web.asp Concentrations of the chemicals may be found in organisms at low trophic levels such as those mentioned, but the animals that prey on them are more greatly affected. EDCs are lipophilic, or fat loving, which means they tend to accumulate and magnify in organisms with higher body fat (Chiuchiolo, Dickhut, Cochran, and others 2004). As one can guess, this leaves the predators at highest tiers of the food web most vulnerable.
The tissues of bowhead whales, bearded and ringed seals, and several species of fish were analyzed gravimetrically and ordered according to lipid content. Experimenters found that the physical and chemical properties of the compounds played a part in the magnitude of bioaccumulation within the organisms tested, reiterating the lipophilic nature of EDCs. In marine mammals, the highest concentrations of EDCs tend to be found in blubber. Among those analyzed, the lipid content of the tissues was the major determining factor in the accumulation of EDCs (Hoekstra, O’Hara, Backus, and others 2005). Other reports of bioaccumulation have been made, including a study on juvenile lobsters, in which it was discovered that endocrine disrupting pesticides entered the body of the lobster through food sources, and were subsequently found to concentrate "up to 125-fold over the surrounding seawater in the hepatopancreas, gonadal tissue, nervous tissue, and epidermal cells of the adult lobster" (Walker, Bush, Puritz, and others 2005).
Endocrine Disruption spans the food webEndocrine disrupting compounds are found in organisms ranging from the base of the food chain up to the highest predators. Many of these creatures are experiencing detrimental effects caused by the EDCs. As previously outlined by Chiuchiolo, Dickhut, Cochran, and others and Dickhut and others (2004), EDCs were discovered in algae, plankton and krill, species important to the proliferation of thousands of other organisms both directly and indirectly. The endocrine disrupting effects of compounds become better illustrated as one climbs up the food chain. Located a step above the organisms mentioned at the base of the web are fish, crustaceans, and echinoderms. Roepke, Snyder, and Cherr (2005) investigated the affect of both groups of EDCs on sea urchin embryonic development. Endocrine disruptors experimented with included 17-beta estradiol, estrone, estriol, bisphenol A, 17-alpha ethinyl estradiol, and others. Normal development of the embryos was inhibited by levels of EDCs tested that matched those found in the environment. Abnormal larvae, delayed development of larvae, inhibited growth and morphological problems were all found as a result of introducing EDCs to developing sea urchin embryos.
Several species of fish have been shown to be affected by EDCs. Lake Apopka, a freshwater lake located in Florida, fell victim to heavy pollution due to an industrial chemical spill. Since then, the lake has been a point of interest for scientists studying the effects of pollutants and in this case endocrine disruptors. Toft and Guillette (2005) found that mosquitofish exposed to water from Lake Apopka had significantly lower sperm counts than fish exposed to water from two other non-polluted lakes and one fresh spring. The Lake Apopka male mosquitofish also experienced a decrease in sexual behavior after their exposure to the contaminated water. The changes in sperm count and sexual behavior were attributed to endocrine disrupting compounds found in Lake Apopka water including a high instance of DDT.
Endocrine disruptors were shown to have dramatic effects on the levels of two very important pituitary sex hormones, namely, growth hormone and prolactin. Growth hormone is important for a wide range of activity in the body, including the lengthening of bones, and stimulation of other organs. Prolactin is also an important hormone, especially for females during and after pregnancy. Elango, Shepherd, and Chen (2006) found that exposing rainbow trout (Ooncorhynchus mykiss) pituitary glands to various levels of EDCs resulted in the disturbance of normal hormonal function. DDT, an estrogenic pesticide caused a major increase in the production of prolactin and growth hormone in trout pituitaries. Treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) a dioxin group contaminant used in Agent Orange, was found to cause an increase in the mRNA coding for growth hormone and prolactin.
Another type of fish, the Japanese medaka (Oryzias latipes) was experimented on by Zha, Wang, and Schlenk (2006). The fish were exposed to pentachlorophenol, a known endocrine disruptor for one month, and then were allowed to reproduce until the F1 generation. Several negative effects were observed, including the decrease in length and body weight of exposed fish, a reduction in the number of eggs produced by the females, as well as an overall decrease in sexual behavior. Most startling was the fact that forty percent of male fish exposed to higher levels of EDCs had an incidence of testis-ova, an inter-sex condition in which oocyte-like cells appear abnormally. Degeneration of the ovaries was observed in female fish in the lower treatment levels, while 66.6% of female fish exposed to the highest level of pentachlorophenol experienced an absence of ovaries altogether.
Endocrine disruptors have been found to dramatically affect both reptiles and amphibians. In one study, conducted by Bogi, Schwaiger, Ferling, and others (2003), water tainted with environmental pollutants from a sewage treatment plant was applied to two different species of frogs, Xenopus laevis and Rana temporaria. Hermaphroditism was observed in both frog species upon exposure to the endocrine disrupting chemicals. Hermaphrodites are often seen in R. temporaria, even during regular undisturbed development, but the phenomenon has not been known to occur in Xenopus, up until the conduction of the experiment. Also noted was an abnormally high female to male ratio, likely to have been due to the endocrine disrupting properties of the chemicals in question. Juvenile alligators from three different Florida locations were experimented on. One location, Belle Glade was considered a higher contaminant site due to its position near sugar cane farming grounds. Lower levels of plasma hormones were found in female alligators from Belle Glade when compared to the other two sites, but was not seen in males. However, reductions in mean phallus tip length and cuff diameter were observed in male alligators living in Belle Glade as compared to those found in the other locations. Other possible causes of these trends were proposed by the scientists, Gunderson and Bermudez and others (2004), who carried out the research, including the exposure to stressful situations, changes or variations in diet, or genetic differences between locations.
EDCs are discovered in higher organismsAs previously described, endocrine disruptors are hypothesized to be entering the environment via aquatic ecosystems. This truth leaves marine mammals especially vulnerable due to the facts that they live in or around the water, they feed on organisms tied to the water, and they are higher up in the food chain, rendering them more susceptible to bioaccumulation. Perched high atop the marine food web are polar bears, (Ursus maritimus). These animals are top predators who have very high levels of body fat, the major contributing factor to bioaccumulation of EDCs. This is why researchers have focused on polar bears a great deal when conducting experiments on endocrine disruptors. One study, by Dietz, Riget, Sonne, and others (2004), researched concentrations of EDCs in the adipose tissue of 92 polar bears from East Greenland. The scientists discovered the presence of several types of endocrine disruptors including PCBs, chlorobenzenes, dieldrin, mirex and DDT in polar bear adipose tissue. It was noted in the study, which was conducted over a period three years, that concentrations fluctuated depending upon the season, sex of polar bear, and period in time which the bears were sampled. Tissue samples from 1999-2001 were compared with those from 1990. The more recent samples had lower concentrations of chlorobenzenes, DDTs, mirex, dieldrin and some other EDCs, but no firm conclusions could be made regarding the actual reduction in environmental pollutants over time due to the variation that occurs between years.
Verreault, Muir, Norstrom, and others (2005) carried out a similar study of polar bear adipose tissue using 107 female polar bears from Alaska, Canada, East Greenland and Svalbard, a small island north of Greenland. These scientists also found that levels of EDCs have been declining over the past decade, but they noted that polar bear adipose tissue sampling might not be a reliable method of studying endocrine disruptors because the tissue is highly influenced by other biological factors. More importantly, the scientists outlined the lack of sufficient research in regards to the effects of endocrine disruptors on polar bears, since most studies have focused simply on the presence of the compounds in the animals. Understandably, this may come as no easy task since polar bears are hard to come by in captivity, and performing experiments on the animals using toxic substances would be considered highly unethical. It is possible that science may not learn of consequent endocrine disruption until irreversible damage has been done. For this reason, the author stresses the importance of further research on EDCs and the eventual decrease or restriction of these harmful substances.
PCBs, pesticides, and DDT breakdown products were discovered in Canadian Arctic beluga whales (Delphinapterus leucas) during an eight-year research project carried out by Stern, Macdonald, Armstrong and others (2005). The blubber of beluga whales from 15 sites was obtained and analyzed gravimetrically to determine the levels of EDCs concentrated in the lipids. The scientists reported finding significant levels of all compounds tested for with notable variation between testing sites. In the discussion, the researches concluded that the age and sex of the animal play a key role in determining contaminant concentration in beluga whales. It was discovered that male belugas had higher levels of EDCs in their blubber. The scientists hypothesized that females have lower contaminant levels because they transfer much of their lipids to their young during pregnancy and lactation. Marsili, D’Agostino, Bucalossi, and others (2004), also mentioned the possibility in their study on striped dolphins, in which they noted that females specimens lose 90% of the organochloride chemicals found in their bodies throughout their pregnancy and during lactation. This study on belugas focused on the actual occurrence of these substances in the blubber of the animals in question. Although Stern, Macdonald, Armstrong and others noted that the compounds they studied have been linked to endocrine disruption and diseases in marine mammals, they did not study endocrine effects on belugas.
Dolphins are another type of marine mammal in which endocrine disruptors have been discovered. One study, performed by Fossi, Marsili, Lauriano, and others (2004), tested the reliability of using non-lethal skin biopsies to determine the concentrations of several different chemicals in striped dolphins (Stenella coeruleoalba). The scientists were successful and named skin biopsy a suitable way to evaluate the chemical contamination of striped dolphins. This comes as good news because skin biopsies are easier for scientists to perform than the extraction of blubber, they are non-lethal and non-stressful to the dolphins, and are still apt for studying bioaccumulation. In the study, gas chromatography was used to detect the incidence of harmful chemicals including DDT and its derivatives, PCBs, organochlorides and others in the skin tissue of the dolphins. Nearly all groups of compounds were detected by the biopsies at levels higher than recommended for marine mammals by the World Health Organization toxic equivalency factors (TEF), which facilitate risk assessment associated with exposure to the chemicals being studied. This research focused mainly on the development of suitable techniques used to investigate the incidence of EDCs in marine mammals such as the striped dolphin.
The Mediterranean striped dolphin was the central organism in another study by Marsili, D’Agostino, Bucalossi, and others (2004), which was carried out to determine the hazard associated with the numerous chemicals detected in their tissues. Using chromatography methods, combined with knowledge of toxic properties of compounds, the scientists were able to create parameters of toxic stress levels. These levels; low, moderate and high, will help to guide future research in evaluating the hazard associated with stress caused by endocrine disrupting substances. The scientists studied striped dolphins in two groups. One group, the stranded dolphins, consists of dead or living specimens who have washed ashore for any number of hypothesized reasons. The other group is the free ranging or swimming dolphins found in open water, which were assumed to be healthy. The tests results found that levels of all organochlorine compounds were higher in stranded dolphins than those of the free ranging group. In the early 1990s, a massive die-off of occurred in which Mediterranean dolphins were killed by the virus Morbilivirus. The scientists used their findings and the toxicological findings from a study on stranded dolphins at the time to confirm that EDCs were instrumental in causing the die-off. Polychlorinated biphenyls were one of the toxic substances found in the dolphins, and PCBs are known to cause immune system disruption, harm to the liver, and to advance and promote disease. It was emphasized that the findings could only be applied to Mediterranean striped dolphins, but even so, the results are alarming.
EDCs omnipresent in environmentIn addition to studies on specific species, there has been research conducted on groups of animals in an area, which helps scientists to understand the collective toxicological status of food webs. Hoekstra, O’Hara, Backus, and others (2005) gathered different tissues from dozens of different species in Alaska including beluga and bowhead whales, ringed and bearded seals, and five types of fish. The researchers found that the concentrations of EDCs in tissues were dependent upon physical and chemical properties of each compound, the lipid content of each tissue, and the dietary habits of each species. This is consistent with the findings of other previously mentioned studies, and reiterates the validity of the process of bioaccumulation. Health Canada, the Federal department responsible for helping maintain and improve the health of Canadian citizens, has set up guidelines for assessing safe concentrations of contaminants in meat, poultry and fish. In the results section of this study, these parameters were used as a guideline to determine the health risks for the animals experimented on. It was found that the PCB levels in the blubber of bowhead whales, beluga whales, bearded seals, and ringed seals, all exceeded the recommended safe level for PCBs in meat proposed by Health Canada. This is not only startling for the health and safety of the affected animals, but it should also be noted that they are used as a food source for many peoples living in northern Alaska, where the animals were sampled. In their conclusion, Hoekstra, O’Hara, Backus, and others (2005) suggested the attainment of further data in regards to EDC concentrations in animals used for consumption, as well as more information on the diet of northern Alaska communities in order to determine the possible health risks to humans.
Vorkamp, Riget, Glasius, and others (2004) conducted another encompassing study, which included several types of terrestrial animals, freshwater fish, marine invertebrates and fish, and marine mammals. The purpose of the experiment was to outline the incidence of chlorobenzenes, pesticides, PCBs, and other endocrine disrupting chemicals in a range of different Greenland biota. The research was very extensive and quite complicated due to the many types of animals and various tissues analyzed. The results from the analysis of chlorobenzene concentration in terrestrial animals were quite interesting. Contrary to nearly all other studies mentioned here, there was no observable correlation between the lipid content and the contaminant concentration. Also, the herbivorous animals had concentrations of EDCs below those found in marine mammals. At first, the results seem puzzling, but they are easily explained by the herbivorous diet kept by the terrestrial organisms being studied. The presence of EDCs was detected in these animals, but they were more likely accumulated into the animal through drinking water rather than food consumption, unlike the marine mammals that feed on organisms such as fish, which leaves them subject to bioaccumulation. In their summary, the scientists explained that all suspected compounds appeared in the various organisms from Greenland, which is a clear indication of the omnipresence of EDCs in the environment.
EDCs are found in various organisms throughout the world, they cause many detrimental effects and they must be stoppedEDCs span the globe and the food webIt is impossible to deny the devastating effects of the persistent compounds causing endocrine disruption in the environment. Organisms are being affected throughout the entire span of the food web. EDCs have been discovered in everything from algae, krill and plankton to alligators, dolphins and terrestrial mammals. After learning of the attempted cover-up by the EPA, it is imperative that information on these controversial substances be brought to light. The chemical structure and biological persistence of EDCs has been well studied and well described through several bioaccumulation studies including those conducted by: Walker, Bush, Puritz, and others (2005), Hohenblum, Gans, Moche and others (2004), and Chiuchiolo, Dickhut, Cochran and others (2004). The ubiquitous presence of endocrine disruptors is demonstrated by the fact that the substances have been found in every corner of the globe. The numerous studies summarized by the author had a wide range of locations throughout the world.
EDCs have affected countless organismsMore importantly, it should be kept in mind that the negative effects of EDCs have been determined in countless organisms. EDCs were shown to adversely affect crustacean development in the study by Roepke, Snyder, and Cherr (2005), in which sea urchin embryonic development was disrupted. The effects of EDCs on fish have been studied a great deal by researchers such as Toft and Guillette (2005), who observed decreased sperm count and sexual behavior in mosquitofish. Zha, Wang, and Schlenk (2006) discovered reduced fertility in Japanese medaka upon application of pentachlorophenol, a pesticide and known EDC. Elango, Shepherd, and Chen, (2006) found that 17-beta estradiol induced significant increases in both pituitary growth hormone and prolactin mRNA in male rainbow trout pituitary glands. Reptiles and amphibians have been found to be responsive to endocrine disrupting substances. Bogi, Schwaiger, Ferling and others (2003) studied two species of frogs in which they discovered induced hermaphroditism and unnatural sex ratios. Variations in sex steroids and decreased phallus size in juvenile alligators are two of the effects observed by Gunderson, Bermudez, Bryan and others in 2004.
EDCs require further investigationThe effect of EDCs on marine mammals is continually being investigated. The presence of these substances has been discovered in species of dolphins, such as the striped dolphin in the studies by Marsili, D’Agostino, Bucalossi and others (2004), and Fossi, Marsili, Lauriano, and others (2004). Various levels of several contaminants were also discovered in Arctic beluga whales by Stern, Macdonald, Armstrong and others (2005). Research projects uncovered the incidence of EDCs in polar bears including those conducted by Verreault, Muir, Norstrom and others (2005), and Dietz, Riget, Sonne and others (2004). Vorkamp, Riget, Glasius and others (2004) discovered EDCs in several marine mammals during their Greenland based study. Though the effects EDCs are having on higher organisms remain under examination, knowledge of endocrine disruption in lower organisms are a good indicator that continuing down this road will end in disaster. Several researchers involved in a variety of studies mentioned the dire need for further investigation, most notably those studying higher organisms that require many expensive resources.
A call to actionObserved effects, and the discovery of EDCs in such a wide variety of organisms should be reason enough to begin establishing restrictions, bans, and other preventative measures. The EPA is currently researching endocrine disruptors in order to determine which substances are most harmful to humans and wildlife. This research could be very lengthy, and by the time conclusions are reached, immeasurable amounts of irreversible damage may already be done. The author proposes placing temporary restrictions on the use of known and suspected endocrine disruptors until conclusive results are obtained. This may seem drastic due to the financial implications, but the possible repercussions of taking no action are priceless. This proposal may seem unrealistic, but the reader can do his or her part to help speed up the process of restricting harmful endocrine disruptors. Ceasing use of products suspected to cause endocrine disruption is one way to help, and writing letters to government officials and EPA members is another. Another important way to promote the cause is to get the word out. Informing friends, family, and anyone who will listen can help to bring a stop to the disruption of the delicate balance found in nature.
References
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http://www.cdc.gov/ncidod/dvbid/westnile/Mapsactivity/surv&control06Maps.htm
Dr. Saleeby joins the staff as Medical/Health writer for The Tea Experience Digest magazine
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