1.1 What is iodine? |
1.2 What happens to iodine when it enters
the environment? |
1.3 How might I be exposed to iodine? |
1.4 How can iodine enter and leave my
body? |
1.5 How can iodine affect my health? |
1.6 How can iodine affect children? |
1.7 How can families reduce the risk of
exposure to iodine? |
1.8 Is there a medical test to determine
whether I have been exposed to iodine? |
1.9 What recommendations has the federal
government made to protect human health? |
1.10 Where can I get more information? |
References |
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April 2004 |
Public Health Statement |
for |
Iodine |
(Iodo) |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for iodine. It is one in a series of Public Health
Statements about hazardous substances and their health effects.
A shorter version, the ToxFAQs™,
is also available. This information is important because this
substance may harm you. The effects of exposure to any hazardous
substance depend on the dose, the duration, how you are exposed,
personal traits and habits, and whether other chemicals are
present. For more information, call the ATSDR Information
Center at 1-888-422-8737.
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This public health statement tells you
about iodine and the effects of exposure.
The Environmental Protection Agency (EPA)
identifies the most serious hazardous waste sites in the nation.
These sites make up the National Priorities List (NPL) and
are the sites targeted for long-term federal cleanup activities.
Iodine has been found in at least 8 sites. Radioactive iodine
has been found at 9 sites, including iodine-129 (129I)
in at least 3 sites, and iodine-131 (131I) in at
least 6 sites of the 1,636 current or former NPL sites. However,
the total number of NPL sites evaluated for iodine is not
known. As more sites are evaluated, the sites at which iodine
is found may increase. This information is important because
exposure to iodine may harm you and because these sites may
be sources of exposure.
When a substance is released from a large
area, such as an industrial plant, or from a container, such
as a drum or bottle, it enters the environment. This release
does not always lead to exposure. You are exposed to a substance
only when you come in contact with it. You may be exposed
by breathing, eating, or drinking the substance, or by skin
contact.
External exposure to radiation may occur
from natural or man-made sources. Naturally occurring sources
of radiation are cosmic radiation from space or radioactive
materials in soil or building materials. Man-made sources
of radioactive materials are found in consumer products, industrial
equipment, atom bomb fallout, and to a smaller extent from
hospital waste and nuclear reactors.
If you are exposed to either radioactive
or stable iodine, many factors determine whether you'll be
harmed. These factors include the dose (how much), the duration
(how long), and how you come in contact with it. You must
also consider the other chemicals you're exposed to and your
age, sex, diet, family traits, lifestyle, and state of health.
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1.1
What is iodine? |
Iodine is a naturally occurring element
that is essential for the good health of people and animals.
Iodine is found in small amounts in sea water and in certain
rocks and sediments. Iodine occurs in many different forms
that can be blue, brown, yellow, red, white, or colorless.
Most forms of iodine easily dissolve in water or alcohol.
Iodine has many uses. Its most important use is as a disinfectant
for cleaning surfaces and storage containers. Iodine is also
used in skin soaps and bandages, and for purifying water.
Iodine is used in medicines. Iodine is added to food, such
as table salt, to ensure that all people in the United States
have enough iodine in their bodies to form essential thyroid
hormones. Iodine is put into animal feeds for the same reason.
Iodine is used in the chemical industry for making inks and
coloring agents, chemicals used in photography, and in making
batteries, fuels, and lubricants. Radioactive iodine also
occurs naturally. Radioactive iodine is used in medical tests
and to treat certain diseases, such as over-activity or cancer
of the thyroid gland.
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1.2
What happens to iodine when it enters the environment? |
The oceans are the most important source
of natural iodine in the air, water, and soil. Iodine in the
oceans enters the air from sea spray or as iodine gases. Once
in the air, iodine can combine with water or with particles
in the air and can enter the soil and surface water, or land
on vegetation when these particles fall to the ground or when
it rains. Iodine can remain in soil for a long time because
it combines with organic material in the soil. It can also
be taken up by plants that grow in the soil. Cows or other
animals that eat these plants will take up the iodine in the
plants. Iodine that enters surface water can reenter the air
as iodine gases. Iodine can enter the air when coal or fuel
oil is burned for energy; however, the amount of iodine that
enters the air from these activities is very small compared
to the amount that comes from the oceans.
Radioactive iodine also forms naturally
from chemical reactions high in the atmosphere. Most radioactive
forms of iodine change very quickly (seconds to days) to stable
elements that are not radioactive. However, one form, 129I,
changes very slowly (millions of years), and its levels build
up in the environment. Small amounts of radioactive iodine,
including 129I and 131I, can also enter
the air from nuclear power plants, which form radioiodine
from uranium and plutonium. Larger amounts of radioactive
iodine have been released to the air from accidents at nuclear
power plants and from explosions of nuclear bombs.
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1.3
How might I be exposed to iodine? |
Iodine is a natural and necessary part
of the food that you eat and the water that you drink. In
the United States, most table salt contains iodine. Iodine
is put into table salt to make sure that everyone has enough
iodine in their bodies to form essential thyroid hormones.
In the past, people in some areas of the United States did
not get enough iodine in their diets. Iodine is in some breads
because it is added to flour to condition bread dough for
baking. Iodine is also in cow and goat milk. Iodine gets into
milk when cows or goats eat iodine that is in their food and
water. Iodine can also get into milk when iodine is used to
clean milking machines and milk storage containers, and to
clean the animals' udders at dairy farms and dairies. Iodine
is in ocean fish, shellfish, and certain plants that grow
in the ocean (kelp). This is because there is iodine in sea
water, and some sea plants and animals concentrate iodine
in their tissues. Iodine can also be in the air. Iodine is
in sea spray and mist, which are tiny drops of sea water.
Iodine is in cleansers and medicines that are used to clean
and bandage skin wounds (tincture of iodine). You can be exposed
to these if they are placed on your skin. Some medicines have
iodine in them. Iodine is used to treat water to make it safe
for drinking. You can buy iodine water purifying tablets that
you add directly to water. You can also buy water treatment
cartridges for your home that have iodine in them. Some iodine
will get into the water that you drink if you use these tablets
or cartridges.
People are almost never exposed to radioactive
iodine, unless they work in a place where radioactive iodine
is used or if they are given radioactive iodine by their doctors.
Radioactive iodine is used in certain medical tests and treatments.
You might have these tests if your doctor needs to look for
problems in your thyroid gland or if your doctor needs to
treat you for a problem with your thyroid gland. In the past,
people were exposed to radioactive iodine released from nuclear
bomb tests, after accidental explosions and fires at nuclear
power plants, or from facilities that processed or used nuclear
fuel for power plants.
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1.4
How can iodine enter and leave my body? |
Most of the iodine that enters your body
comes from the food that you eat. A smaller amount comes from
the water that you drink. Iodine will enter your body if it
is in the air that you breathe. Some forms of iodine can enter
your body when placed on the skin. Iodine can also be injected
into your blood by your doctor for special medical tests or
treatments. Iodine that enters your body quickly goes into
your thyroid gland, a small important organ in your neck.
Iodine is used in the thyroid gland to make hormones that
are needed for growth and health. Almost all of the iodine
in your body is in your thyroid gland. Iodine that does not
go into your thyroid gland leaves the body in your urine in
a few weeks to months. Small amounts of iodine can also leave
your body in sweat or in breast milk. Iodine that leaves your
body each day is usually replaced by the iodine that you eat
in your food, so that the amount of iodine in your body is
just enough to keep you healthy.
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1.5
How can iodine affect my health? |
Iodine is needed for your thyroid gland
to produce thyroid hormones. You and your thyroid gland are
healthy when there is just enough iodine in your body, about
10-15 milligrams, so that just the right amount of thyroid
hormones are produced. This amount would look like much less
than a pinch of table salt if placed in your hand. This amount
of iodine is in most people when they eat the foods that people
normally eat in the United States. Your thyroid gland can
become unhealthy if more or less than this amount of iodine
is in your body. An unhealthy thyroid gland can affect your
entire body. If the thyroid gland cannot make enough hormone,
then you would have to be given thyroid hormone in pills.
If your thyroid gland makes too much hormone, then you would
have to be given drugs to make your thyroid make less hormone.
Radioactive iodine can also be unhealthy for your thyroid
gland. If too much radioactive iodine enters your body, the
radioactive iodine will destroy your thyroid gland so that
the gland will stop making hormones. Too much radioactive
iodine in your body can also cause thyroid nodules or cancer.
To protect the public from the harmful
effects of toxic chemicals and to find ways to treat people
who have been harmed, scientists use many tests.
One way to see if a chemical will harm
people is to learn how the chemical is absorbed, used, and
released by the body. In the case of a radioactive chemical,
it is also important to gather information concerning the
radiation dose and the dose rate to the body. For some chemicals,
animal testing may be necessary. Animal testing may also be
used to identify health effects such as cancer or birth defects.
Without laboratory animals, scientists would lose a basic
method to get information needed to make wise decisions to
protect public health. Scientists have the responsibility
to treat research animals with care and compassion. Laws today
protect the welfare of research animals, and scientists must
comply with strict animal care guidelines.
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1.6
How can iodine affect children? |
This section discusses potential health
effects from exposures during the period from conception to
maturity at 18 years of age in humans.
Babies and children need iodine to form
thyroid hormones, which are important for growth and health.
If infants and children do not have enough iodine in their
bodies, their thyroid glands will not produce enough thyroid
hormone and they will not grow normally. If they have too
much iodine in their bodies, they may develop an enlarged
thyroid gland (goiter), which may not produce enough thyroid
hormone for normal growth. We also need just the right amount
of iodine from our mothers before we are born. Too much iodine
from the mother can cause a baby's thyroid gland to be so
large that it makes breathing difficult or impossible. Not
enough iodine from the mother can cause a baby to not produce
enough thyroid hormone, which can affect growth and mental
development of the baby. Radioactive iodine in food can be
more harmful to babies and children than to adults. When radioactive
iodine is in the air, it can get onto the grass and water
that the cows eat and drink. Infants and children drink a
lot more milk than most adults. If there is radioactive iodine
in the milk that a child or infant drinks, more iodine will
enter the thyroid gland of the child than of an adult who
drinks less milk. In addition, because the thyroid gland of
a child or infant is smaller than that of an adult, a child's
thyroid gland will receive a higher radiation dose than an
adult. Children are more sensitive to the harmful toxic effects
of iodine and radioactive iodine than adults because their
thyroid glands are still growing and the thyroid gland tissues
are more easily harmed by radioactive iodine, and because
children need a healthy thyroid gland for normal growth.
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1.7
How can families reduce the risk of exposure to iodine? |
We all are exposed to iodine in the food
that we eat and in the water that we drink. Iodine is needed
for your good health. We do not want to prevent exposure to
iodine, but we do want to try to prevent exposure to too much
iodine. This is not likely to happen from eating a normal
diet in the United States or from drinking water or breathing
air. It could happen if you were careless about storing soaps
or cleansers or medicines that have iodine in them. For example,
a child could swallow medicines that contain iodine. People
are rarely exposed to radioactive iodine, unless they work
in a place where radioactive iodine is used or if they are
given radioactive iodine by their doctors for certain medical
tests or treatments.
If your doctor finds that you have been
exposed to significant amounts of iodine, ask whether your
children might also be exposed. Your doctor might need to
ask your state health department to investigate.
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1.8
Is there a medical test to determine whether I have been exposed
to iodine? |
Most physicians do not test for iodine
in their offices, but can collect samples and send them to
special laboratories. They can also feel the thyroid for lumps
that may have been caused by disease or past exposure to radioactive
iodine, but the results do not tell the cause. Every person's
body contains a small amount of iodine, but normally not radioactive
iodine (such as 131I). Iodine can be measured in
the blood, urine, and saliva. The amount is normally measured
by its mass (in grams). If the iodine is radioactive, it can
be measured by its mass or by its radiation emissions. These
emissions are used to tell the amount of radioactive iodine
(in curies or becquerels) and the radiation dose it gives
to your body (in sieverts or rem).
Radiation detectors can measure radioactive
iodine inside your body using the radiation coming from the
thyroid gland in your neck. This is useful only if you recently
inhaled or ingested some, or if your physician recently gave
you some for medical purposes. Your body quickly eliminates
iodine and radioactive iodine, so tests should be done shortly
after exposure.
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1.9
What recommendations has the federal government made to protect
human health? |
The federal government develops regulations
and recommendations to protect public health. Regulations
can be enforced by law. Federal agencies that develop
regulations for toxic substances include the Environmental
Protection Agency (EPA), the Occupational Safety and Health
Administration (OSHA), the Food and Drug Administration (FDA),
the Department of Energy (DOE), and the U.S. Nuclear Regulatory
Commission (USNRC).
Recommendations provide valuable guidelines
to protect public health but cannot be enforced by
law. Federal organizations that develop recommendations for
toxic substances include the Agency for Toxic Substances and
Disease Registry (ATSDR), the National Institute for Occupational
Safety and Health (NIOSH), and the FDA.
Regulations and recommendations can be
expressed in not-to-exceed levels in air, water, soil, or
food that are usually based on levels that affect animals;
then they are adjusted to help protect people. Sometimes these
not-to-exceed levels differ among federal organizations because
of different exposure times (an 8-hour workday or a 24-hour
day), the use of different animal studies, or other factors.
Recommendations and regulations are also
periodically updated as more information becomes available.
For the most current information, check with the federal agency
or organization that provides it. Some regulations and recommendations
for iodine include the following:
The National Research Council has established
a Recommended Dietary Allowance for iodine of 150 micrograms
per day (µg/day), with additional allowances of 25 µg/day
during pregnancy and 50 µg/day during nursing. The EPA
has established regulations that limit releases of certain
forms of radioactive iodine to the environment and require
that industries report releases of certain forms of radioactive
iodine. NIOSH has established recommendations for limits of
worker exposures to iodine and radioactive iodine. The Nuclear
Regulatory Commission, the National Council of Radiation Protection
and Measurements (NRCP) and the International Commission of
Radiological Protection (ICRP) have established recommended
limits for worker exposures to radioactive iodine and for
releases of radioactive iodine to the environment.
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1.10
Where can I get more information? |
If you have any more questions or concerns, please contact
your community or state health or environmental quality department or:
Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Information line and technical assistance:
Phone: 888-422-8737
FAX: (770)-488-4178
ATSDR can also tell you the location of occupational and environmental health
clinics. These clinics specialize in recognizing, evaluating, and treating illnesses
resulting from exposure to hazardous substances.
To order toxicological profiles, contact:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Phone: 800-553-6847 or 703-605-6000
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References |
Agency for Toxic Substances and Disease
Registry (ATSDR). 2004. Toxicological
profile for iodine. Atlanta, GA: U.S. Department of Health
and Human Services, Public Health Service.
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