September 1995 |
ToxFAQs™ |
for |
Thallium |
(Talio) |
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This fact sheet answers the most frequently
asked health questions about thallium. For more information,
you may call the ATSDR Information Center at 1-888-422-8737.
This fact sheet is one in a series of summaries about hazardous
substances and their health effects. 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.
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SUMMARY: Exposure to thallium
occurs mainly from eating food. Exposure to higher levels
of thallium may occur in the workplace. Breathing high
levels of thallium may result in effects on the nervous
system, while ingesting high levels of it results in vomiting,
diarrhea, temporary hair loss, and other effects. This
chemical has been found in at least 210 of 1,416 National
Priorities List sites identified by the Environmental
Protection Agency. |
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What
is thallium? |
Pure thallium is a bluish-white metal
that is found in trace amounts in the earth's crust. In the
past, thallium was obtained as a by-product from smelting
other metals; however, it has not been produced in the United
States since 1984. Currently, all the thallium is obtained
from imports and from thallium reserves.
In its pure form, thallium is odorless
and tasteless. It can also be found combined with other substances
such as bromine, chlorine, fluorine, and iodine. When it's
combined, it appears colorless-to-white or yellow.
Thallium is used mostly in manufacturing
electronic devices, switches, and closures, primarily for
the semiconductor industry. It also has limited use in the
manufacture of special glass and for certain medical procedures.
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What
happens to thallium when it enters the environment? |
- Thallium enters the environment primarily from coal-burning
and smelting, in which it is a trace contaminant of the
raw materials.
- It stays in the air, water, and soil for a long time and
is not broken down.
- Some thallium compounds are removed from the atmosphere
in rain and snow.
- It's absorbed by plants and enters the food chain.
- It builds up in fish and shellfish.
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How
might I be exposed to thallium? |
- Eating food contaminated with thallium may be a major
source of exposure for most people.
- Breathing workplace air in industries that use thallium.
- Smoking cigarettes.
- Living near hazardous waste sites containing thallium
(may result in higher than normal exposures).
- Touching or, for children, eating soil contaminated with
thallium.
- Breathing low levels in air and water.
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How
can thallium affect my health? |
Exposure to high levels of thallium can
result in harmful health effects. A study on workers exposed
on the job over several years reported nervous system effects,
such as numbness of fingers and toes, from breathing thallium.
Studies in people who ingested large
amounts of thallium over a short time have reported vomiting,
diarrhea, temporary hair loss, and effects on the nervous
system, lungs, heart, liver, and kidneys. It has caused death.
It is not known what the effects are from ingesting low levels
of thallium over a long time.
Birth defects were not reported in the
children of mothers exposed to low levels from eating vegetables
and fruits contaminated with thallium. Studies in rats, however,
exposed to high levels of thallium, showed adverse developmental
effects.
It is not known if breathing or ingesting
thallium affects human reproduction. Studies showed that rats
that ingested thallium for several weeks had some adverse
reproductive effects. Animal data suggest that the male reproductive
system may be susceptible to damage by low levels of thallium.
There is no information available on
the health effects of skin contact with thallium in people
or animals.
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How
likely is thallium to cause cancer? |
The Department of Health and Human Services,
the International Agency for Research on Cancer, and the Environmental
Protection Agency (EPA) have not classified thallium as to
its human carcinogenicity.
No studies are available in people or
animals on the carcinogenic effects of breathing, ingesting,
or touching thallium.
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Is
there a medical test to show whether I've been exposed to thallium? |
There are medical tests available to
measure levels of thallium in urine and hair. In addition,
thallium can also be measured in blood; however, this is not
a good indicator of exposure since thallium only stays in
blood a very short time.
These tests require special equipment
that is not usually available in most doctor's offices. In
addition, these tests cannot determine if adverse health effects
will occur from the exposure to thallium.
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Has the federal government made recommendations to protect human health? |
The EPA requires that discharges or accidental
spills into the environment of 1,000 pounds or more of thallium
be reported.
The Occupational Safety and Health Administration
(OSHA) has set an exposure limit of 0.1 milligrams per cubic
meter (0.1 mg/m³) for thallium in workplace air. The
American Conference of Governmental Industrial Hygienists
(ACGIH) has established the same guidelines as OSHA for the
workplace.
The National Institute for Occupational
Safety and Health (NIOSH) has recommended that 15 mg/m³
of thallium be considered immediately dangerous to life and
health. This is the exposure level of a chemical that is likely
to cause permanent health problems or death.
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Glossary |
Carcinogenicity: Ability to cause cancer.
Ingesting: Taking food or drink into
your body.
Milligram (mg): One thousandth of a gram.
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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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Where can I get more information? |
ATSDR can tell you where to find occupational
and environmental health clinics. Their specialists can recognize,
evaluate, and treat illnesses resulting from exposure to hazardous
substances. You can also contact your community or state health
or environmental quality department if you have any more questions
or concerns. For more information, contact:
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Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Phone: 1-888-42-ATSDR (1-888-422-8737)
FAX: (770)-488-4178
Email: ATSDRIC@cdc.gov
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