Public Health Statement for Carbon Tetrachloride
Spanish: Tetracloruro de Carbono
CAS#: 56-23-5
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for Carbon Tetrachloride. 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.
This public health statement tells you
about carbon tetrachloride and the effects of exposure to
it.
The Environmental Protection Agency (EPA)
identifies the most serious hazardous waste sites in the nation.
These sites are then placed on the National Priorities List
(NPL) and are targeted for long-term federal clean-up activities.
Carbon tetrachloride has been found in at least 430 of the
1,662 current or former NPL sites. Although the total number
of NPL sites evaluated for this substance is not known, the
possibility exists that the number of sites at which carbon
tetrachloride is found may increase in the future as more
sites are evaluated. This information is important because
these sites may be sources of exposure and exposure to this
substance may harm you.
When a substance is released either from
a large area, such as an industrial plant, or from a container,
such as a drum or bottle, it enters the environment. Such
a release does not always lead to exposure. You can be 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.
If you are exposed to carbon tetrachloride,
many factors will determine whether you will 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
any other chemicals you are exposed to and your age, sex,
diet, family traits, lifestyle, and state of health.
What is carbon tetrachloride?
Carbon tetrachloride is a clear liquid
that evaporates very easily. Most carbon tetrachloride that
escapes to the environment is therefore found as a gas. Carbon
tetrachloride does not easily burn. Carbon tetrachloride has
a sweet odor, and most people can begin to smell it in air
when the concentration reaches 10 parts carbon tetrachloride
per million parts of air (ppm). It is not known whether people
can taste it or, if they can, at what level. Carbon tetrachloride
is a manufactured chemical and does not occur naturally in
the environment.
Carbon tetrachloride has been produced
in large quantities to make refrigeration fluid and propellants
for aerosol cans. Since many refrigerants and aerosol propellants
have been found to affect the earth's ozone layer, the production
of these chemicals is being phased out. Consequently, the
manufacture and use of carbon tetrachloride has declined a
great deal.
In the past, carbon tetrachloride was
widely used as a cleaning fluid (in industry and dry cleaning
establishments as a degreasing agent, and in households as
a spot remover for clothing, furniture, and carpeting). Carbon
tetrachloride was also used in fire extinguishers and as a
fumigant to kill insects in grain. Most of these uses were
discontinued in the mid-1960s. Until recently, carbon tetrachloride
was used as a pesticide, but this was stopped in 1986.
What happens to carbon tetrachloride when it enters the environment?
Because carbon tetrachloride evaporates
easily, most of the compound released to the environment during
its production and use reaches the air, where it is found
mainly as a gas. It can remain in air for several years before
it is broken down to other chemicals. Small amounts of carbon
tetrachloride are found in surface water. Because it evaporates
easily, much of it will move from surface water to the air
within a few days or weeks. However, it may be trapped in
groundwater for longer periods. Carbon tetrachloride is not
expected to stick to soil particles. If spilled onto the ground,
much of it will evaporate to the air. Some of it may also
go into groundwater, where it can remain for months before
it is broken down to other chemicals. It is not expected to
build up in fish. We do not know if it builds up in plants.
How might I be exposed to carbon tetrachloride?
Very low background levels of carbon
tetrachloride are found in air, water, and soil because of
past and present releases. Concentrations in air of 0.1 part
carbon tetrachloride per billion parts of air (ppb) are common
around the world, with somewhat higher levels often found
(0.2-0.6 ppb) in cities. Carbon tetrachloride is also found
in some drinking water supplies, usually at concentrations
less than 0.5 ppb. Exposure to levels of carbon tetrachloride
higher than these typical "background" levels is
likely to occur only at specific industrial locations where
carbon tetrachloride is still used or near chemical waste
sites where emissions into air, water, or soil are not properly
controlled. Exposure at such sites could occur by breathing
carbon tetrachloride present in the air, by drinking water
contaminated with carbon tetrachloride, or by getting soil
contaminated with carbon tetrachloride on the skin. Young
children may also be exposed if they eat soil that contains
carbon tetrachloride. Carbon tetrachloride has been found
in water or soil at about 26% of the waste sites investigated
under Superfund, at concentrations ranging from less than
50 to over 1,000 ppb.
People who work with carbon tetrachloride
are likely to receive the greatest exposure to the compound.
The National Institute for Occupational Safety and Health
(NIOSH) estimates that 58,208 workers are potentially exposed
to carbon tetrachloride in the United States. The average
daily intake of carbon tetrachloride for the general population
is estimated to be 0.1 microgram (Āµg per kg of body
weight). The estimated average daily amount that the general
population may drink in water is 0.01 Āµg per kg of body
weight.
How can carbon tetrachloride enter and leave my body?
Carbon tetrachloride can enter your body
through your lungs if you breathe air containing carbon tetrachloride,
or through your stomach and intestines if you swallow food
or water containing carbon tetrachloride. Carbon tetrachloride
can also pass through the skin into the body. When you inhale
carbon tetrachloride, over 30-40% of what you inhale enters
your body, where most of it temporarily accumulates in body fat. Some can enter the kidney, liver, brain, lungs, and skeletal
muscle. When you drink water contaminated with carbon tetrachloride,
about 85-91% of it can enter your body. Much of the compound
that enters your body when you breathe it or drink water contaminated
with it leaves your body quickly, and a lot of it can be found
in your breath within a few hours. Animal studies have shown
that under differing conditions, 34-75% of carbon tetrachloride
leaves the body in expired air, 20-62% leaves the body in
feces, and only low amounts leave the body in the urine. Animal
studies also suggest that it may take weeks for the remainder
of the compound in the body to be eliminated, especially that
which has entered the body fat. Most of the carbon tetrachloride
is eliminated from your body unchanged, but some of it may
be changed to other chemicals before removal from the body
(for example, chloroform, hexachloroethane, and carbon dioxide).
Chloroform and hexachloroethane may themselves cause harmful
effects.
How can carbon tetrachloride affect my health?
Scientists use many tests to protect
the public from harmful effects of toxic chemicals and to
find ways for treating persons who have been harmed.
One way to learn whether a chemical will
harm people is to determine how the body absorbs, uses, and
releases the chemical. For some chemicals, animal testing
may be necessary. Animal testing may also help identify health
effects such as cancer or birth defects. Without laboratory
animals, scientists would lose a basic method for getting
information needed to make wise decisions that protect public
health. Scientists have the responsibility to treat research
animals with care and compassion. Scientists must comply with
strict animal care guidelines because laws today protect the
welfare of research animals.
Most information on the health effects
of carbon tetrachloride in humans comes from cases where people
have been exposed to relatively high levels of carbon tetrachloride,
either only once or for a short period, for example, by accidental
poisoning or by working with the chemical in a confined space
without ventilation. Experiments have not been performed on
the effects of long-term exposure of humans to low levels
of carbon tetrachloride, so the human health effects of such
exposures are not known.
The liver is especially sensitive to
carbon tetrachloride since it contains a large amount of the
enzymes that change the form of the chemical. Some of the
breakdown products may attack cell proteins, interfering with
the functions of the liver cells. Products that attack cell
membranes may result in the death of the cells. In mild cases,
the liver becomes swollen and tender, and fat builds up inside
the organ. In severe cases, liver cells may be damaged or
destroyed, leading to a decrease in liver function. Such effects
are usually reversible if exposure is not too high or too
long.
The kidney is also sensitive to carbon
tetrachloride. Less urine may be formed, leading to a buildup
of water in the body (especially in the lungs) and buildup
of waste products in the blood. Kidney failure often was the
main cause of death in people who died after very high exposure
to carbon tetrachloride. Long-term breathing exposure to carbon
tetrachloride worsened age related kidney disease in rats.
Fortunately, if injuries to the liver
and kidney are not too severe, these effects eventually disappear
after exposure stops. This is because both organs can repair
damaged cells and replace dead cells. Function usually returns
to normal within a few days or a few weeks after the exposure
has stopped.
After exposure to high levels of carbon
tetrachloride, the nervous system, including the brain, is
affected. Such exposure can be fatal. The immediate effects
are usually signs of intoxication, including headache, dizziness,
and sleepiness perhaps accompanied by nausea and vomiting.
These effects usually disappear within 1-2 days after exposure
stops. In severe cases, stupor or even coma can result, and
permanent damage to nerve cells can occur.
Carbon tetrachloride also causes effects
on other tissues of the body, but these are not usually as
common or important as the effects on the liver, kidney, and
brain.
There have been no studies of the effects
of carbon tetrachloride on reproduction in humans, but studies
in rats showed that long-term inhalation may cause decreased
fertility.
Studies in animals have shown that swallowing
or breathing carbon tetrachloride over a period of years increases
the frequency of liver tumors. Mice breathing carbon tetrachloride
also developed tumors of the adrenal gland. Studies have not
been performed to determine whether swallowing or breathing
carbon tetrachloride causes tumors in humans, but it should
be assumed that carbon tetrachloride could produce cancer.
The Department of Health and Human Services (DHHS) has determined
that carbon tetrachloride may reasonably be anticipated to
be a carcinogen (i.e., cause cancer). The International Agency
for Research on Cancer (IARC) has classified carbon tetrachloride
in Group 2B, possibly carcinogenic to humans. EPA has determined
that carbon tetrachloride is a probable human carcinogen.
Many reported cases of carbon tetrachloride
toxicity are associated with drinking alcohol. The frequent
drinking of alcoholic beverages increases the danger of organ
damage from carbon tetrachloride exposure. This enhanced effect
has been shown in situations in which a group of workers were
exposed to carbon tetrachloride in air, but only those who
were heavy consumers of alcohol became ill.
How can carbon tetrachloride affect children?
This section discusses potential health
effects in humans from exposures during the period from conception
to maturity at 18 years of age.
Children and adults may be exposed to
low levels of carbon tetrachloride in drinking water. Small
children who live near factories that produce or use carbon
tetrachloride could accidentally eat some of the chemical
by putting dirty hands in their mouths, but the amount of
carbon tetrachloride in the soil is thought to be too low
to be harmful. Carbon tetrachloride is no longer used in consumer
products, but children could breathe in vapors if households
are still using old supplies.
It is not known if the way in which carbon
tetrachloride is absorbed into and eliminated from the body
is different in children than it is in adults, but the processes
are likely to be similar. Compared to adults, young children
have lower amounts of the enzyme that converts carbon tetrachloride
to a harmful chemical. The health effects of carbon tetrachloride
have not been studied in children, but they are likely to
be similar to those seen in adults exposed to the chemical.
There is no direct evidence that maternal
exposure to carbon tetrachloride has a harmful effect on the
fetus in humans. A few human survey-type studies suggest that
maternal drinking water exposure to carbon tetrachloride might
possibly be related to certain birth defects, such as low
birthweight and small size at birth. Information from animal
studies indicates that carbon tetrachloride may cause early
fetal deaths, but does not cause birth defects in babies surviving
to term. However, these animal studies did not test for neurological
damage in exposed newborn babies.
One study calculated that carbon tetrachloride
is likely to pass from the maternal circulation into breast
milk. Thus, it is possible that children could be exposed
to carbon tetrachloride from breast feeding, but the levels
of exposure are likely to be low.
How can families reduce the risk of exposure to carbon tetrachloride?
If your doctor finds that you have been
exposed to substantial amounts of carbon tetrachloride, ask
whether your children might also have been exposed. Your doctor
might need to ask your state health department to investigate.
Although most consumer uses of carbon
tetrachloride have been banned, children may be exposed to
carbon tetrachloride in old consumer household cleaning products.
Removing these old containers will reduce your family's risk
of exposure to carbon tetrachloride. Household chemicals should
be stored out of the reach of children to prevent accidental
poisonings and skin burns. Always store household chemicals
in their original containers. Never store household chemicals
in containers that children would find attractive to eat and
drink from, such as old soda bottles. Keep your poison control
center's number next to your phone.
Sometimes older children sniff household
chemicals in an attempt to get high. Your children may be
exposed to carbon tetrachloride by intentionally inhaling
products containing it. Talk with your children about the
dangers of sniffing chemicals.
Is there a medical test to determine whether I have been exposed
to carbon tetrachloride?
Several very sensitive and specific tests can detect carbon
tetrachloride in exposed persons. The most convenient way
is simply to measure carbon tetrachloride in exhaled air,
but carbon tetrachloride can also be measured in blood, fat,
or other tissues. Because special equipment is needed, these
tests are not routinely performed in doctors' offices, but
your doctor can refer you to where you can obtain such a test.
Although these tests can show that a person has been exposed
to carbon tetrachloride, the test results cannot be used to
reliably predict whether any bad health effects might result.
Because carbon tetrachloride leaves the body fairly quickly,
these methods are best suited to detecting exposures that
have occurred within the last several days.
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. The EPA, the Occupational Safety and
Health Administration (OSHA), and the Food and Drug Administration
(FDA) are some federal agencies that develop regulations for
toxic substances. Recommendations provide valuable guidelines
to protect public health, but cannot be enforced by law. The
Agency for Toxic Substances and Disease Registry (ATSDR) and
the National Institute for Occupational Safety and Health
(NIOSH) are two federal organizations that develop recommendations
for toxic substances.
Regulations and recommendations can be
expressed as "not-to-exceed" levels, that is, levels
of a toxic substance in air, water, soil, or food that do
not exceed a critical value that is usually based on levels
that affect animals; they are then adjusted to levels that
will help protect humans. Sometimes these not-to-exceed levels
differ among federal organizations because they used different
exposure times (an 8-hour workday or a 24-hour day), different
animal studies, or other factors.
Recommendations and regulations are also
updated periodically 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 carbon tetrachloride include the following:
To protect the general public from exposure
to carbon tetrachloride, the federal government has limited
or banned the use of this compound in most common household
products and fire extinguishers, and has discontinued its
use as a pesticide. To protect workers who use carbon tetrachloride
while on the job, the OSHA has set a maximum concentration
limit in workplace air of 10 ppm for an 8-hour workday over
a 40-hour work week. EPA has also set limits on how much carbon
tetrachloride can be released from an industrial plant into
waste water and is preparing to set limits on how much carbon
tetrachloride can escape from an industrial plant into outside
air. To ensure that drinking water supplies are safe, EPA
has set a Maximum Contaminant Level (MCL) for carbon tetrachloride
of 5 parts per billion (ppb), based on analytical detection
limits in drinking water. Because carbon tetrachloride is
possibly carcinogenic to humans, a Maximum Contaminant Level
Goal (MCLG) of zero has been proposed.
References
Agency for Toxic Substances and Disease Registry (ATSDR). 2005. Toxicological profile for Carbon Tetrachloride. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.
Where can I get more information?
If you have questions or concerns, please contact your community or state health or environmental quality department or:
For more information, contact:
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
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.