estrogen in lakes and rivers

7/30/2019 Estrogen in Lakes and Rivers

1/12

Estrogen in Lakes and RiversBioaccumulation and Feminization in fish

Date: 12/26/2012

Name: Linda Kvastad

Personal number: 870217-0427

e-mail:[email protected]@kth.se
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


2/12

Table of ContentSummary ................................................................................................................................................. 2

Introduction ............................................................................................................................................. 3

Background .......................................................................................................................................... 3

Estrogen in Lakes and Rivers ................................................................................................................... 5

Whole lake experiment collapse of a fish population ...................................................................... 5

Bioaccumulation in wild fish................................................................................................................ 7

Feminization of fish by environmental estrogens ............................................................................... 8

Discussion and conclusions ................................................................................................................... 10

References ............................................................................................................................................. 11

Articles ............................................................................................................................................... 11

Books ................................................................................................................................................. 11


3/12

SummaryEstrogen induced feminization of fish populations has been detected at different locations

throughout the world. This causes fish to have problems with reproduction, which consequently

reduces the fish population in number at exposed sites. I find it an important research area since

estrogen contamination seems to have the ability to kill fish populations due to reproductive

problems, and bioaccumulate in adipose tissue, which in turn could further spread the estrogen

exposure to predators higher up in the food chain.

Todays knowledge of estrogens and estrogen-like compounds show where most of the

contamination come from, which is wastewater treatment plants and different industry. We know its

toxic for exposed fish and we know estrogens may have the possibility to bioaccumulate in adipose

tissue. We also have good biomarkers to detect effects in fish when they have been exposed. This

has been investigated by different research groups and will be discussed and presented in this

report. What we dont know is how estrogen contamination will affect us after long term exposure if

we continue to pollute our environment and I think that research on how to take care of estrogens

and estrogen-like compounds is needed.


4/12

IntroductionToday it is known that we release a lot of estrogens and estrogen-like compounds into our

environment [1]. Different research groups have been investigating what effect this has on the

wildlife, especially fish [1] [2] [3]. Is estrogen contamination toxic for fishes? In what way is the fish

population effected? Can estrogens bioaccumulate in the fish we eat, and are the estrogen-like

compounds in the environment dangerous for us humans?

Background

Estrogen is a steroid hormone produced in the ovary, and it is hydrophobic and derives from

cholesterol [6]. Through endocrine signaling, estrogen travels in the bodys circulatory system from

its production site to targeted cells at distant sites. Estrogens purpose is to stimulate maintenance

and development of the female reproductive system [5].

As a small hydrophobic signaling molecule, estrogen has to diffuse across the plasma membrane of

the targeted cell to reach its receptor in the nucleus. An overview of the mechanism of this is show in

Figure 1. In the nucleus the estrogen receptor is inactive in the absence of estrogen, and bound toHsp90 chaperone. When estrogen enters the nucleus and binds to its receptor, Hsp90 is displaced

which allows dimerization of estrogen and its receptor. This complex then binds to DNA and in

association with histone acetyltransferase (HAT) it stimulates transcription of targeted genes [5].

Figure 1 Overview of estrogens interaction with its receptor in a cell[5].


5/12

How do we measure estrogens and estrogen-like compounds effect on fish? A biomarker often used

is vitellogenin (VTG). This protein is produced during vitellogenesis where yolk is produced. During

this process VTG is synthesized in the liver and taken up by growing oocytes (eggs). VTG is then

stored as yolk and will serve as food reserve for developing embryos. The expression of the

vitellogenin gene is controlled by hormones, and mainly estrogens, in particular 17-estradiol (E2). E2

is synthesized in the ovary and after release it will stimulate liver cells to produce VTG Figure 2 [1]

[4].

Figure 2 Hormonal control, by 17-estradiol (E2), of vitellogenin (VTG) production in female fish.

One of the reasons for using TVG as a biomarker to measure how estrogenic contamination effect

the fish population is because E2 is considered to be the main hormone to stimulate synthesis of VTG.

This means that the increase of VTG in female fish is correlated with the increase of E2 during sexual

maturation. For example, during the female salmons seasonal reproductive cycle VTG concentration

in the ovary increase around one million fold. This enables the female salmon to grow thousands oflarge yolky oocytes and may comprise as much as up to 25% of the females bodyweight. This means

that the plasma concentration of VTG in a female fish varies a lot throughout a year and makes it

possible to create a very sensitive bioassay by measuring VTG in fish. Although male fish normally

express a very low concentration of VTG, it is possible to induce VTG expression in male fish via

exposure of estrogen or estrogen-like compounds, which is another good reason to use VTG as a

biomarker [4].

Estrogens are not only synthesized in our bodies, since estrogen-like compounds are detected in our

environment, but where do the environmental estrogens come from? And how are they spread into

our environment? The biggest source of leakage of estrogens and estrogen-like compounds into ourenvironment seems to be from wastewater treatment-plants and major industry such as: the plastic

industry, the soap and detergent industry, agriculture, the plastic industry and the petrochemical

industry [4]. This prompts questions such as to what we should do about the estrogenic

contamination. How big is the problem? How far does the contamination spread, is it local to specific

sites or does it spread worldwide? If it affects the wildlife, such as fish, which is our food, will it affect

us too? What can we do to stop it?


6/12

Estrogen in Lakes and RiversHere follows three cases where researchers have looked into the effect estrogenic contamination has

had on fish populations in different contexts.

Whole lake experiment collapse of a fish population

It is known that water released from wastewater treatment-plants is a complex mixture and that it

contains estrogen and estrogen-like compounds, which in turn can affect the reproductive capability

of male fishes. It has previously been noted that male fishes that are exposed to estrogen and

estrogen-like compounds increase their vitellogenin (VTG) production and researchers have also

found formation of early-stage eggs in the male fishs testis after exposure. This feminization of the

exposed male fish has been due to natural estrogens such as 17-estradiol (E2), synthetic estrogens

such as 17-ethynylestradiol (EE2) used in birth-control pills or weaker estrogen mimics. In this study

the researchers wanted to know what long term affect this exposure would have on the fish

population [1].

To investigate the long term effect off estrogenic contamination on a fish population, the researchers

conducted a 7-year whole lake experiment. This was done in Canada in the years 1999-2005. The

experimental lake called Lake 260, was exposed to levels of EE2 within the same range of

concentration noted earlier in released water from wastewater treatment-plants. Two nearby lakes

were used as reference, Lake 114 and Lake 442. During the 7-year experiment measurements were

made on the level of VTG protein in the fishes, and also tissue samples of female fish ovary and male

fish testis were taken. Samples were taken from all three lakes 2 years before the addition of EE2 to

Lake 260 started, the exposure continued for 3 years and after that there were 2 years without

exposure [1].

The results from measurements of VTG protein show a significant increase in both male and female

fishes seeFigure 3. The female fishes in the reference lakes had only 2.5% of the amount of VTG that

the female fishes in the exposed Lake 260 had. The male fishes showed levels of VTG a thousand

times greater than that of the reference lakes. This high production of VTG in male fish in Lake 260

was sustained in all of the 3 years which the lake was exposed. It is notable that due to low catches

of fish during the last 2 years of the study in Lake 260 this analysis could not continue [1].


7/12

Figure 3 VTG concentration in male (lower) and female (upper) fish[1].

During examination of gonadal tissue samples, the feminization of male fish could be observed. At

the end of the time period of estrogenic exposure four of nine male fishes captured in Lake 260

showed presence of primary-stage oocytes in their testicular tissue seeFigure 4 [1].

Figure 4 Testicular tissue from reference Lake 442 (left). Testicular tissue from experimental Lake 260, arrows indicate

primary-stage oocytes (right)[1].

From this 7-year whole lake experiment the researchers showed that fish populations exposed to

estrogenic contamination experienced decreased reproductive capabilities and eventually the

studied species died out due to these reproductive difficulties [1].


8/12

Bioaccumulation in wild fish

It is known that estrogen exposure of fish will disrupt their endocrine signaling and result in change

in development, growth and reproduction following exposure. One of these endocrine disrupting

chemicals (EDCs) is 17-ethynylestradiol (EE2) used in birth-control pills. When EDCs such as this is

released into the environment it causes feminization of male fishes and is a threat to the exposed

fish population. Even very low concentrations of estrogenic substances can cause adverse effects, for

example in male zebrafish 0,2-10ng/L of EE2 is enough to induce synthesis of VTG. At concentration

of 5ng/L of EE2 it has also been observed that male zebrafish show altered behavior in their courtship

towards the females, which lead to spawning failure. Since of EE2 has shown adverse effects in fish

and we are releasing it out into our environment and fish is one of our food sources, researchers

wanted to investigate if it was possible for of EE2 to bioaccumulate in fish [2].

The researchers conducted a study in a river in Canada that was previously known to be

contaminated from industrial and municipal effluents. The St. Clair River is 64 km and samples of fish

was collected directly downstream from a wastewater treatment plant (WWTP) and reference fish

samples were collected 26 km downstream from WWTP. Then they measured the VTG protein and

EE2 content of the sampled fishes [2].

After measurements of VTG protein levels in fishes from exposed and reference sites, the result

showed that the female fishes from both sites had similar levels of VTG whereas no VTG was

detected in males from the reference site and eight of ten males from the exposed site had

detectable levels of VTG. When measuring the level of EE2 in fishes, 50% from the exposed site had

detectable levels of EE2, and the detection limit was 0,45ng/g. The estimated mean of EE2

concentration was similar between males (1,64ng/g) and females (1,43ng/g). Fish from the reference

site had no detectable levels of EE2. When correlating the EE2 concentration and the lipid content in

the fishes, a significant positive correlation was found seeFigure 5. Since this type of relationship is

expected for bioaccumulating substances it is reasonable to assume that EE2 may have the ability to

bioaccumulate in adipose tissue [2]. This in turns raises the question what happens to predators

further up in the food chain that eats these fishes, such as us humans. If we eat EE2 bioaccumulated

in adipose tissue, will our bodies absorb EE2 and become affected by it?

Figure 5 A significant positive correlation between EE2 concentration and lipid content in fish from estrogenic contaminatedsite [2].


9/12

Feminization of fish by environmental estrogens

Throughout the world it has been reported that fish exposed to estrogen during longer times are

becoming feminized. This is of great concern, especially since even low concentrations, in the nano-

gram per liter range, is enough to induce an effect in fish. When a fish population becomes feminized

a number of abnormal effects are observed. The sex ration of the population will become biased in

favor of females, some individuals will have both ovarian and testicular tissue (intersex individuals),

the fishes will become sexually mature at a later age, and sperm production will be disrupted,

histological alteration in gonad tissue and a change in their reproductive behavior [3].

Different techniques exist to measure the occurrence of estrogen in water, such as liquid

chromatography, gas chromatography and mass spectrometry. Although these methods are highly

sensitive, they cannot measure how a mix of different estrogenic compounds will affect a fish

population. Therefor a research group set up an in vivo bioassay to measure this effect on fish [3].

Chinas largest river, Yangtze River, and close to its delta the city Nanjing is situated. From this city a

lot of effluent form wastewater treatment plants (WWTPs) is released into the river, also upstream

wastewater and untreated sewage enters the river further up. In recent years it has been reported

that the number of fish are decreasing, are becoming smaller in size and younger in years. The

research group took water from three different sections of the Yangtze River, and exposed male gold

fishes to this estrogenic contaminated water in different dilutions (25%, 50% and 100%) over a short

time (14 days). Control fish was treated only with dechlorinated municipal water. In the study they

measured serum VTG protein, 17-estradiol (E2) serum concentrations, and gonadosomatic index

(GSI) which is the gonads weight in proportion to the fishs total body mass [3].

After measurements of VTG concentrations, a trend was observed where higher concentrations of

VTG occurred if the fish was exposed during longer time and with a higher concentration of the water

from WWTPs contaminated with estrogenic substances, seeFigure 6 [3].

Figure 6 In male gold fish, VTG serum levels after exposure of different dilutions of water from Jiangxinzhou section of

Yangtze River [3]


10/12

Measurement of E2 concentrations showed a trend that increased river water also increased the

concentration of E2 in fish seeFigure 7 [3].

Figure 7 In male gold fish, E2 serum concentration after exposure of different dilutions of water from Jiangxinzhou section

of Yangtze River [3]

The trend from GSI measurements where that fish exposed to higher concentration of river water

had a decreased GSI, seeFigure 8, which is consistent with reproduction problems [3].

Figure 8 In male gold fish, GSI (%) after exposure of different dilutions of water from Jiangxinzhou section of Yangtze River

[3]


11/12

Discussion and conclusionsToday we know more about how estrogenic contaminations effect our environment thanks to

research groups around the world. We are aware that we release estrogens and estrogen-like

compounds from different industries and from our wastewater treatment plants. We also have

methods of detecting if the fish populations are affected from this contamination, where the protein

vitellogenin (VTG) is a very promising biomarker.

Researchers have proof that estrogen contamination is toxic for fish populations when they are

exposed during a longer period. The fish population becomes feminized and is experiencing

reproductive issues, which will cause the exposed fish population to die out if measures are not

taken to prevent to estrogenic contamination.

Research results also indicate that estrogens can bioaccumulate in adipose tissue in fish. I believe

that this is a very important area to do more research within. Especially to investigate if predators

higher up in the food chain will become affected by eating fish that contains higher than normal

concentrations of estrogens. Who eat the fish? Are other animals in the environment, such as birds,

also experiencing feminization? Is estrogenic contamination something that only affects animals

close to wastewater treatment plants and industry releasing estrogens and estrogen-like

compounds? How far do the adverse effects spread? Will it continue to spread? As shown in one

study where the control sample was taken downstream of the exposed site and showed no VTG

expression [2]. If the same study is repeated in a few years, will there be a different result? If the fish

populations upstream die out, will the estrogenic contamination spread and kill more?

I think it is very important to determine how big problem the estrogenic contamination really is and if

it is spreading. I hope that observations are made over longer periods of time to see if it is so. This is

important when making decisions on what to do to prevent estrogenic contamination. If it doesnt

spread and is only local, I personally believe that further research will have difficulties with their

fundings, maybe it is not a big enough threat to spend money on? I personally dont believe that, I

believe that the estrogenic contamination will spread if for example fish populations close to an

exposed site die out. I think that maybe fish populations upstream work as a buffer against further

spreading of the estrogenic contamination to populations downstream, of for example wastewater

treatment plants.

I believe that it is important to investigate exactly where all these estrogenic compounds come from

and evaluate if there are other alternatives that could be used. Also if there is a need to develop new

techniques in wastewater treatment to take care of the estrogens.


12/12

References

Articles

[1] K. A. Kidd, P. J. Blanchfield, K. H. Mills, et al., Collapse of fish population after exposure to a

synthetic estrogen. PNAS 21, 8897-8901 (2007).

[2] A. M. Al-Ansari, A. Saleem, L. E. Kimpe, et al., Bioaccumulation of the phatmaceutical 17-

ethinylestradiol in shorthead redhorse suckers (Moxostoma macrolepidotum) from the St. Clair River,

Canada. Environmental Pollution 158, 2566-2571 (2010).

[3] G. H. Lu, W. T. Song, C. Wang, et al., Assessment of in vivo estrogenic response and the

identification of environmental estrogens in the Yangtze River (Nanjing section). Chemosphere 80,

982-990 (2010).

[4] J. P. Sumpter, S. Jobling, Vitellogenesis as a Biomarker for Estrogenic Contamination of the

Aquatic Environment. Environmental Health Perspectives 103, 173-178 (1995).

Books[5] Geoffrey M. Cooper, Robert E. Hausman. The Cell: A Molecular Approach, fourth edition. ISBN-10:

0-87893-220-8. pp 49, 282-283,600-603.

[6] Jeremy M. Berg, John L. Tymoczko, Lubert Stryer. Biochemistry, sixth edition. ISBN-10: 0-7167-

8724-5. pp 749-754, 907-909.

estrogen in lakes and rivers

Documents