Download Endocrine Disruptors: Atrazine

Endocrine Disruptors: Atrazine
Jonathan Shalom
Dr. Blumberg
Bio Sci 2B
April 20th, 2005
What is the Endocrine System and what is its purpose?
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Composition of many glands (ovaries, testes, thyroid, parathyroid, adrenal)
Some of these glands secrete hormones while others produce chemicals or fluids.
Hormones produced by the endocrine glands enter the capillaries of the blood
circulatory system. They trigger different effects by targeting specific "receptors" in the
organs.
The ES is important because it coordinates and regulates many essential body functions
Examples:
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reproduction and embryo development;
production, use and storage of energy;
balance and maintenance of water and salt (electrolytes) in the body; and
reaction to stimuli (e.g., fright, excitement).
Some Examples of Common Hormones
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Examples of hormones secreted by the ES that would effect the biological
function of an individual :
1.
ACTH (adrenocorticotrophic hormone) - produced by the pituitary gland to
influence the release of corticosteroid hormones from the adrenal glands,
ADH (anti-diuretic hormone, vasopressin) - produced by the pituitary gland to
stimulate water reabsorption by the kidney tubules
Adrenaline (epinephrine) and noradrenaline (norepinephrine) - two hormones
formed in the adrenal gland that help the body to react (e.g., flight or fight, body
defense mechanisms) under stressful conditions (they can increase the heart rate,
blood pressure, blood sugar levels, blood clotting rate),
Estrogen - a female sex hormone produced by the ovaries,
Insulin - secreted by the pancreas and regulates the storage and use of
carbohydrates in the body
Thyroid Hormone - produced in the thyroid and influences the function of virtually
every cell in the body (growth, development and metabolism).
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Source: http://www.ccohs.ca/
Disruption of the ES
The Endocrine System may be disrupted in one of three
ways:
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A substance may imitate a natural hormone and lock onto a
receptor within the cell.
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A substance can bind to a receptor within a cell and thus
prevent the correct hormone from binding.
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The disruptors can interfere or block the way natural hormones
and receptors are made or controlled.
Atrazine: Profile
Purpose: Used as an Herbicide/ Pesiticide to control grasses
and broadleaf weeds
Other Chemical Names: 1,3,5-Triazine-2,4-diamine, 6-chloro-Nethyl-N'-(1-methylethyl)- , 1-Chloro-3-ethylamino-5-isopropylamino2,4,6-triazine,etc.
Toxicity: Termed PAN Bad Actor Chemical
Physical Appearance:
White powder that is not very volatile, reactive,
or flammable and that will dissolve in water.
Atrazine: Connection with Environment
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Primarily enters environment through spraying on farm crops.
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Atrazine is taken up by the plants growing in the soil or is
broken down over a period of days to months.
or
It may wash from the soil into streams where it will stay for a
long time
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If atrazine enters the air, it may be broken down by reactions
with chemicals in the air, or it may adhere to particles such as
dust which eventually settle out of the air.
The Problem
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Leopard frogs are in the middle of mating
season when farmers are using
herbicides
Atrazine water levels are highest when
frogs are going through critical stages of
development
Frogs and other amphibians living in
waters with high Atrazine levels were
found to have multiple gonads and
altered sexual development
Exposure to Atrazine
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Inhaling: The intake of dust (commonly by rural residents). If their water
supply is contaminated, they could breathe atrazine as they cook,
bathe, or do laundry.
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Ingestion: People who have contaminated drinking water may be
exposed to low levels of atrazine. Some low-level exposure to atrazine
may occur when treated crops are eaten or handled. People who
handle contaminated soil could ingest traces of the herbicide if they eat
or touch their mouths with dirty hands.
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Touching: Atrazine is not absorbed through the skin
Chemical Process
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Receptors, which are incorporated into the plasma membrane, are proteins that function as ligand-activated
transcription factors. They regulate the formation of proteins in many tissues.
Some ligands can bind to several different nuclear receptors. Also, despite the conservation of receptors,
individual ligands induce expression of different biological responses in different species and tissues.
Process: Part 2
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According to research, data supports the hypothesis that a
hormone diffuses to the cell nucleus, binds non-covalently to
the Endoplasmic Reticulum, dimerizes, and changes shape.
The shape allows it to attach to one of many potential DNA
docking sites
The attachment triggers the formation of a transcription
complex and activates a specific gene in the body.
Substances, such as atrazine, prevent this binding, and
therefore cause deformities among organisms.
Since the endocrine disruptor already takes up the original
location of the hormone (activation site), the hormone
continues to try to attach itself to the cell.
However, after failing to attach itself to the original cell, the
hormone seeks a new cell to attach to, which results in an
abnormal accumulation of hormones.
Phenotypic Effects On Organisms
• Atrazine could affect pregnant women by causing their babies to grow more slowly than
normal or by causing them to give birth early.
•Atrazine has been shown to slow down the development of fetuses in animals, and exposure
to high levels of atrazine during pregnancy caused reduced survival of fetuses
•Atrazine has been shown to cause changes in blood hormone levels in animals that affected
ovulation and the ability to reproduce. These effects are not expected to occur in humans
because of specific biological differences between humans and these types of animals.
•Atrazine also caused liver, kidney, and heart damage in animals; it is possible that atrazine
could cause these effects in humans, though this has not been examined.
• Not enough information is available to state whether atrazine causes cancer in humans.
There may be a link between atrazine use and various types of cancer, but we still do not
know.
Controls to Endocrine Disruptors
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The majority of the more than 2,000 chemicals that come onto the
market every year do not go through even the simplest tests to
determine toxicity.
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Therefore, many governments are implementing new laws
requiring strict testing on new chemicals to help humanity and the
environment.
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Will be banned in all European countries
by 2005
Environmental Protection Agency has
only placed a limit on Atrazine use in the
United States and has not banned it
entirely
Location of Endocrine Disruptors
Interesting Facts
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Atrazine is one of the most widely used herbicide in the U.S. Between 74-80
million pounds of atrazine are used each year in the U.S.
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The U.S. Environmental Protection Agency has identified 200 community
water systems where atrazine has been detected at levels that approached
or exceeded the agency's Maximum Contaminant Level (MCL). Of the 200,
eight community water systems have annual average readings that
significantly exceed the MCL.
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In 1995, more than 80 percent of atrazine applications -- nearly 54 million
pounds -- were applied to U.S. corn crops.
Source: http://www.checnet.org
What Can You Do?
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Learn and research about endocrine disruptors, and spread
the word to your family and friends.
If possible, buy organic foods.
Instead of using pesticides to kill pests, use traps or baits as a
substitution.
Keeping your house clean can prevent the invasion of pests.
Make sure the fish that you eat from lakes or rivers are not
contaminated.
Avoid heating food in plastic containers
Do not give young children soft plastic or toys
Thank Your For Listening…
THE END