1.1 What is n-hexane? |
1.2 What happens to n-hexane when
it enters the environment? |
1.3 How might I be exposed to n-hexane? |
1.4 How can n-hexane enter and
leave my body? |
1.5 How can n-hexane affect my
health? |
1.6 How can n-hexane affect children? |
1.7 How can families reduce the risk of
exposure to n-hexane? |
1.8 Is there a medical test to determine
whether I have been exposed to n-hexane? |
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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July 1999 |
Public Health Statement |
for |
n-Hexane |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for n-hexane. 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 n-hexane 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.
n-Hexane has been found in at least 60 of the 1,467 current
or former NPL sites. However, the total number of NPL
sites evaluated for this substance is not known. As
more sites are evaluated, the sites at which n-hexane
is found may increase. This information is important because
exposure to this substance 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.
If you are exposed to n-hexane,
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 n-hexane? |
n-Hexane is a chemical made from
crude oil. Pure n-hexane is a colorless liquid
with a slightly disagreeable odor. It evaporates very
easily into the air and dissolves only slightly in water.
n-Hexane is highly flammable, and its vapors can be
explosive.
Pure n-hexane is used in laboratories.
Most of the n-hexane used in industry is mixed with
similar chemicals in products known as solvents. Common
names for some of these solvents are "commercial hexane,"
"mixed hexanes," "petroleum ether," and "petroleum naphtha."
An older name for these types of solvents is "petroleum benzine."
Several hundred million pounds of n-hexane are produced
in the United States each year in the form of these solvents.
The major use for solvents containing n-hexane is to
extract vegetable oils from crops such as soybeans.
They are also used as cleaning agents in the printing, textile,
furniture, and shoemaking industries. Certain kinds
of special glues used in the roofing and the shoe and leather
industries also contain n-hexane. Several consumer
products contain n-hexane. For example, gasoline contains
about 1–3% n-hexane. n-Hexane is also
present in rubber cement.
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1.2
What happens to n-hexane when it enters the environment? |
n-Hexane enters the air, water,
and soil during its manufacture and use. Wastes containing
n-hexane are sometimes disposed of in landfills.
n-Hexane can enter the environment from these landfills.
n-Hexane also enters the environment from accidental
spills during transport and leaks from storage containers.
n-Hexane evaporates very easily
into the air. Once in the air, n-hexane can react
with oxygen and be broken down. n-Hexane released
into the air is broken down in a few days.
If n-hexane is spilled into a
lake or river, a very small portion will dissolve in the water,
but most will float on the surface. The n-hexane
will then evaporate into the air. The n-hexane
dissolved in the water can be broken down by certain types
of bacteria, although it is not known how long this takes.
If n-hexane is spilled on the
ground, much of it will evaporate into the air before it penetrates
the soil. Any n-hexane that penetrated the soil
would probably be broken down by bacteria. If n-hexane
leaks from an underground storage tank, it will float on the
groundwater, rather than mixing with it since n-hexane
is lighter than water.
n-Hexane is not stored or concentrated
by plants, fish, or animals.
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1.3
How might I be exposed to n-hexane? |
Since gasoline contains n-hexane,
almost everyone is exposed to small amounts of n-hexane
in the air. The n-hexane in gasoline is released
into the air at service stations and in automobile exhaust.
Some people may also be exposed by spilling gasoline on their
skin. The concentration of n-hexane in the air
in Chicago was recently measured and contained 2 parts n-hexane
per 1 billion parts air (2 ppb). n-Hexane has
generally not been found in most foods or drinking water,
so you are not likely to be exposed by eating or drinking.
Because cooking oils are processed with solvents containing
n-hexane, very small amounts may be present in these
products. However, the amounts in cooking oil are too
low to have any effect on people.
People living near hazardous waste sites
containing n-hexane or near its manufacturing, processing,
or storage facilities could potentially be exposed.
Because of the chemical properties of n-hexane, the
most likely way a person would be exposed is by breathing
in air contaminated with n-hexane. A less likely
way for a person to be exposed is by drinking contaminated
private well water.
You may be exposed to n-hexane
if you use products containing it at work. This exposure
will mainly be by breathing in air containing n-hexane,
but you can also be exposed through your skin by contact with
substances containing n-hexane. Some occupational groups
that may be exposed to n-hexane include refinery workers,
shoe and footwear assembly workers, laboratory technicians,
workers operating or repairing typesetting and printing machinery,
construction workers, carpet layers, carpenters, auto mechanics
and gas station employees, workers in plants manufacturing
tires or inner tubes, and workers in air transport and air
freight operations. Exposure can also occur in the home
if products containing n-hexane are used without proper
ventilation.
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1.4
How can n-hexane enter and leave my body? |
n-Hexane can enter your body through
your lungs if it is in the air you breathe. It can also
enter your body through your stomach and intestines if it
is in your drinking water or food, or through your skin if
you come into contact with it. How much n-hexane
enters your body depends on how long you are exposed and the
amount to which you are exposed.
Once you inhale n-hexane, it goes
into your bloodstream and is carried to all the organs in
your body. Enzymes in your liver break down n-hexane.
If you are exposed to high concentrations of n-hexane
over a long period, one of these breakdown products may cause
damage to your nervous system. Most of these breakdown
products leave your body in the urine within a day or two.
n-Hexane and its breakdown products are not stored
in your body.
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1.5
How can n-hexane affect my health? |
Almost all the people known to have had
their health affected by exposure to n-hexane used
it at work. In the 1960s and early 1970s, several outbreaks
of nerve disorders occurred among shoe workers in Japan and
Italy. Doctors determined the disease was caused by
the workers breathing air containing high concentrations of
n-hexane. The n-hexane came from glues
and solvents the workers used in assembling the shoes.
In one group of workers in Japan, it was estimated that the
workers who became ill had been breathing air containing 500–2,500
parts n-hexane per million parts air (500–2,500 ppm)
for 8–14 hours a day for 6 months to several years.
The first symptom that the affected workers had was a feeling
of numbness in their feet and hands. This was followed
by muscle weakness in the feet and lower legs. If exposure
continued, the symptoms grew worse. In some workers,
paralysis of the arms and legs developed. When the affected
workers were examined by doctors, the nerves controlling the
muscles in their arms and legs were found to be damaged.
The medical term for this condition is "peripheral neuropathy"
(peripheral means outside the brain and spinal cord; neuropathy
means nerve damage). Fortunately, once the workers were
removed from exposure to n-hexane they recovered within
6 months to a year, although some of the more severely affected
did not fully recover for 1–2 years.
Poor ventilation of the work area was
a major factor in all of these cases. Workers who became
ill usually worked in their homes or in very small workshops.
Since the 1970s, workplace ventilation has been improved and
levels of n-hexane in the air have been lower.
There have been very few cases of nerve damage from n-hexane
since 1980. A few people have also suffered nerve damage
from "sniffing" products containing n-hexane.
Like cases in the workplace, the number of cases due to sniffing
has fallen since the 1970s.
It is not known if oral or skin exposure
to n-hexane can cause these effects in people. There
have been very few documented exposures to n-hexane by these
routes in people.
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 hurt
people is to learn how the chemical is absorbed, used, and
released by 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.
When rats are exposed to n-hexane in
the air, they show signs of damage to their nervous systems
very similar to those seen in people who became ill after
workplace exposure. As in people, these effects in rats
depend on the concentrations of n-hexane in air and how long
exposure lasts. Studies in rats showed that a breakdown
product of n-hexane (called 2,5-hexanedione) causes
the nerve damage, not n-hexane itself. Testing
for 2,5-hexanedione in the urine can be used to determine
if a person has been exposed to potentially harmful amounts
of n-hexane. Studies in rats also showed that n-hexane
can cause nerve damage when given orally in very large doses.
At very high levels of n-hexane
in air (1,000–10,000 ppm), signs of damage to sperm-forming
cells in male rats occurred. Damage to the lungs occurred
in rabbits and mice. People have rarely been exposed
to these high levels of n-hexane, so it is not known
if these effects would occur in people.
It is not known if exposure to n-hexane
can affect fertility in people. Experiments done with
animals that were fed or breathed in n-hexane did not
show any effect on fertility.
There is no evidence that exposure to
n-hexane increases the risk of cancer in people.
No reliable information is available on whether n-hexane
causes cancer in animals. In an animal experiment with
commercial hexane (which contains n-hexane), an increase
in liver cancer was found in female mice after exposure for
2 years. No increase was found in male mice or in rats of
either sex. Commercial hexane is a mixture, and we do
not know what parts of the mixture caused the cancer in the
female mice. n-Hexane has not been characterized
for carcinogenicity by the Department of Health and Human
Services (DHHS), the International Agency for Research on
Cancer (IARC), or the Environmental Protection Agency (EPA).
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1.6
How can n-hexane affect children? |
This section discusses potential health
effects from exposures during the period from conception to
maturity at 18 years of age in humans. Potential effects
on children resulting from exposures of the parents are also
considered.
Harmful effects from exposure to n-hexane
have mainly occurred in adults. This is because most
known cases have occurred in workers. However, it is
probable that if children were exposed to n-hexane
at levels that cause harmful effects in adults, similar effects
would occur. We do not know whether children differ
from adults in their susceptibility to health effects from
n-hexane exposure. Only a few animal studies
have compared the effects of n-hexane between adults
and young animals. In these studies, the young animals
were somewhat less likely to have harmful effects on their
nervous system from breathing n-hexane than the adults,
but more likely to die from a large oral dose.
Experiments in rats and mice have shown
little effect of n-hexane exposure on the development
of the fetus. It is probable that n-hexane and
its breakdown products can cross the placenta and also be
excreted in breast milk, but no accurate measurements have
been made in people. n-Hexane and its breakdown products
have been detected in the fetus when pregnant rats were exposed
to n-hexane.
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1.7
How can families reduce the risk of exposure to n-hexane? |
If your doctor finds that you have been
exposed to significant amounts of n-hexane, ask whether
your children might also be exposed. Your doctor might
need to ask your state public health department to investigate.
Certain products used in the home may
contain n-hexane, for example, some quick-drying glues
and cements used in hobbies. These products should be
kept out of the reach of children and only used with proper
ventilation. Always store household chemicals in their
original, labeled containers. Never store household
chemicals in containers children would find attractive to
eat or drink from, such as old soda bottles. Keep your
Poison Control Center's number by the phone.
Sometimes older children sniff household
chemicals in an attempt to get "high." Your children
may be exposed to n-hexane by inhaling products containing
it. Talk with your children about the dangers of sniffing
chemicals. Sniffing products containing n-hexane
has caused paralysis of the arms and legs in teenagers in
the United States and Europe.
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1.8
Is there a medical test to determine whether I have been exposed
to n-hexane? |
If you have been exposed to harmful amounts
of n-hexane, the amount of one of its breakdown products
(2,5-hexanedione) will probably be increased in your urine.
Your doctor will have to send a sample to a specialized laboratory.
This test can only detect n-hexane exposure occurring
within 2–3 days before the test, since 2,5-hexanedione leaves
the body within a few days 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), and the Food and Drug Administration
(FDA). 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) and the National Institute for Occupational
Safety and Health (NIOSH).
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 n-hexane include the following:
OSHA has set a Permissible Exposure Limit
(PEL) of 500 ppm for n-hexane in workplace air.
A court decision struck down a proposed PEL of 50 ppm.
Damage to nerves has been found in people at 500 ppm.
The American Conference of Governmental Industrial Hygienists
(ACGIH) recommends a Threshold Limit Value (TLV) of 50 ppm.
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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). 1999. Toxicological
profile for n-hexane. Atlanta, GA: U.S. Department
of Health and Human Services, Public Health Service.
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