1.1 What is thallium? |
1.2 How might I be exposed to thallium? |
1.3 How can thallium enter and leave my
body? |
1.4 How can thallium affect my health? |
1.5 Is there a medical test to determine
whether I have been exposed to thallium? |
1.6 What recommendations has the federal
government made to protect human health? |
1.7 Where can I get more information? |
References |
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July 1992 |
Public Health Statement |
for |
Thallium |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for thallium. 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 Statement was prepared to give you
information about thallium and to emphasize the human health
effects that may result from exposure to it. The Environmental
Protection Agency (EPA) has identified 1,177 sites on its
National Priorities List (NPL). Thallium has been found in
at least 18 of these sites. However, we do not know how many
of the 1,177 NPL sites have been evaluated for thallium. As
EPA evaluates more sites, the number of sites at which thallium
is found may change. This information is important for you
to know because thallium may cause harmful health effects
and because these sites are potential or actual sources of
human exposure to thallium.
When a chemical 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 as a chemical
emission. This emission, which is also called a release, does
not always lead to exposure. You can be exposed to a chemical
only when you come into contact with the chemical. You may
be exposed to it in the environment by breathing, eating,
or drinking substances containing the chemical or from skin
contact with it.
If you are exposed to a hazardous chemical
such as thallium, several factors will determine whether harmful
health effects will occur and what the type and severity of
those health effects will be. These factors include the dose
(how much), the duration (how long), the route or pathway
by which you are exposed (breathing, eating, drinking, or
skin contact), the other chemicals to which you are exposed,
and your individual characteristics such as age, sex, nutritional
status, family traits, life style, and state of health.
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1.1
What is thallium? |
Pure thallium is a soft, bluishwhite
metal that is widely distributed in trace amounts in the earth's
crust. In its pure form, it is odorless and tasteless. It
can be found in pure form or mixed with other metals in the
form of alloys. It can also be found combined with other substances
such as bromine, chlorine, fluorine, and iodine to form salts.
These combinations may appear colorless to white or yellow.
Thallium remains in the environment since it is a metal and
cannot be broken down to simpler substances.
Thallium exists in two chemical states
(thallous and thallic). The thallous state is the more common
and stable form. Thallous compounds are the most likely form
to which you would be exposed in the environment. Thallium
is present in air, water, and soil. We do not know how much
time it takes for thallium to move from one medium to another.
Thallium is used mostly in the manufacture
of electronic devices, switches, and closures. It also has
limited use in the manufacture of special glasses and for
medical procedures that evaluate heart disease. Up until 1972
thallium was used as a rat poison, but was then banned because
of its potential harm to man. Thallium is no longer produced
in the United States. All the thallium used in the United
States since 1984 has been obtained from imports and thallium
reserves.
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1.2
How might I be exposed to thallium? |
You can be exposed to thallium in air,
water, and food. However, the levels of thallium in air and
water are very low. The greatest exposure occurs when you
eat food, mostly homegrown fruits and green vegetables
contaminated by thallium. Small amounts of thallium are released
into the air from coalburning power plants, cement factories,
and smelting operations. This thallium falls out of the air
onto nearby fruit and vegetable gardens. Thallium enters food
because it is easily taken up by plants through the roots.
Very little is known on how much thallium is in specific foods
grown or eaten. Cigarette smoking is also a source of thallium.
People who smoke have twice as much thallium in their bodies
as do nonsmokers. Although fish take up thallium from water,
we do not know whether eating fish can increase thallium levels
in your body. It has been estimated that the average person
eats, on a daily basis, 2 parts thallium per billion parts
(ppb) of food. Even though rat poison containing thallium
was banned in 1972, accidental poisonings from old rat poison
still occur, especially in children.
Thallium is produced or used in power
plants, cement factories, and smelters. People who work in
these places can breathe in the chemical or it may come in
contact with their skin. Information on the amount of thallium
in workplace air in the United States could not be found.
Hazardous waste sites are also possible sources of exposure
to thallium. An average of 23 ppb of thallium in surface water
and 11 ppb in groundwater have been found at hazardous waste
sites. Since thallium compounds mix easily in water, you can
be exposed if you live near a chemical waste site where thallium
emissions have contaminated the water. An average of 1.7 parts
of thallium per million parts (ppm) of soil was found at hazardous
waste sites. Since thallium sticks to soil, you can be exposed
at hazardous waste sites if you swallow or touch contaminated
soil. Thalliumcontaminated dust in the air can also be
swallowed after it is cleared from the lungs. Thallium is
naturally found in soil at levels from 0.3 to 0.7 ppm.
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1.3
How can thallium enter and leave my body? |
Thallium can enter your body when you
eat food or drink water contaminated with thallium, breathe
thallium in the air, and when your skin comes in contact with
it. When thallium is swallowed most of it is absorbed and
rapidly goes to various parts of your body, especially the
kidney and liver. Thallium leaves your body slowly. Most of
the thallium leaves your body in urine and to a lesser extent
in feces. It can be found in urine within 1 hour after exposure.
After 24 hours, increasing amounts are found in feces. It
can be found in urine as long as 2 months after exposure.
About half the thallium that enters various parts of your
body leaves them within 3 days.
The significant, likely routes of exposure
near hazardous waste sites are through swallowing thalliumcontaminated
soil or dust, drinking contaminated water, and skin contact
with contaminated soil.
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1.4
How can thallium affect my health? |
Thallium can affect your nervous system,
lung, heart, liver, and kidney if large amounts are eaten
or drunk for short periods of time. Temporary hair loss, vomiting,
and diarrhea can also occur and death may result after exposure
to large amounts of thallium for short periods. Thallium can
be fatal from a dose as low as 1 gram. No information was
found on health effects in humans after exposure to smaller
amounts of thallium for longer periods. Birth defects observed
in children of mothers exposed to small amounts of thallium
did not occur more often than would be expected in the general
population. The length of time and the amount of thallium
eaten by the mothers are not known exactly. As in humans,
animal studies indicate that exposure to large amounts of
thallium for brief periods of time can damage the nervous
system and heart and can cause death. Animal reproductive
organs, especially the testes, are damaged after drinking
small amounts of thalliumcontaminated water for 2 months.
These effects have not been seen in humans. No information
was found on effects in animals after exposure to small amounts
of thallium for longer periods of time. No studies were found
on whether thallium can cause cancer in humans or animals.
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1.5
Is there a medical test to determine whether I have been exposed
to thallium? |
Reliable and accurate ways to measure
thallium in the body are available. The presence of thallium
in the urine and hair can indicate exposure to thallium. Tests
of your urine can detect thallium up to 2 months. The normal
amount of thallium in human urine amounts to less than 1 ppm
and 5–10 ppb in human hair. Although thallium can be measured
in blood, this tissue is not a good indicator of exposure
since thallium stays there too short a time. We do not know
yet whether thallium levels measured in the body can be used
to predict possible health effects.
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1.6
What recommendations has the federal government made to protect
human health? |
The federal government has set standards
and guidelines to protect individuals from the possible effects
of excessive thallium exposure. The EPA has determined a water
quality criteria level of 13 ppb in surrounding waters to
protect humans from the harmful effects of drinking water
and eating food containing thallium.
The Occupational Safety and Health Administration
(OSHA) has established an occupational limit of 0.1 mg of
soluble thallium compounds per cubic meter of workplace air
(mg thallium/m³/skin) for an 8-hour workday over a 40-hour
workweek. "Skin" indicates that measures must be taken to
prevent skin exposure to thallium.
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1.7
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). 1992 Toxicological profile
for thallium. Atlanta, GA: U.S. Department of Health and
Human Services, Public Health Service.
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