1.1 What is methyl mercaptan? |
1.2 How might I be exposed to methyl mercaptan? |
1.3 How can methyl mercaptan enter and
leave my body? |
1.4 How can methyl mercaptan affect my
health? |
1.5 Is there a medical test to determine
whether I have been exposed to methyl mercaptan? |
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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September 1992 |
Public Health Statement |
for |
Methyl Mercaptan |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for methyl mercaptan. 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 methyl mercaptan and to emphasize the human
health effects that may result from exposure to it. The Environmental
Protection Agency (EPA) has identified 1,300 sites on its
National Priorities List (NPL). Methyl mercaptan has been
found in at least 2 of these sites. However, we do not know
how many of the 1,300 NPL sites have been evaluated for methyl
mercaptan. As EPA evaluates more sites, the number of sites
at which methyl mercaptan is found may change. This information
is important for you to know because methyl mercaptan may
cause harmful health effects and because these sites are potential
or actual sources of human exposure to methyl mercaptan.
When a chemical is released from a source,
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 methyl mercaptan, 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 methyl mercaptan? |
Methyl mercaptan, also known as methanethiol,
is a colorless gas with a smell like rotten cabbage. It is
a natural substance found in the blood, brain, and other tissues
of humans and other animals, and it is released from animal
feces. It occurs naturally in certain foods such as some nuts
(filberts) and cheese (Beaufort).
Methyl mercaptan is released from decaying
organic matter in marshes and is present in the natural gas
of certain regions of the United States, in coal tar, and
in some crude oils. Methyl mercaptan is manufactured for use
in pesticides, as a jet fuel additive, in the plastics industry,
and in making methionine, a nutrient that is added to poultry
feed. Methyl mercaptan is also released as a decay product
of wood in pulp mills.
We know very little about what happens
to methyl mercaptan after it is released to the environment.
Because it is a gas, most of it probably goes into the air.
Sunlight can break it down into other substances. If methyl
mercaptan is released to soil, it probably then goes into
the air or is carried through the soil by rain or any other
water that contacts it.
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1.2
How might I be exposed to methyl mercaptan? |
Methyl mercaptan is always present in
your body and in your urine and feces. It can also be present
in the breath of persons with liver damage. You can be exposed
to methyl mercaptan in the air if you live near a natural
source of this gas, such as a marsh, an underground gas pocket,
or a dump site that releases it. We have no information on
the levels of methyl mercaptan that come from these sources.
Methyl mercaptan has not been found in
drinking water, so you would probably not be exposed to it
in this way. Methyl mercaptan is a natural part of certain
foods, such as nuts and cheeses. It has also been approved
for use as a food additive. Because of its unpleasant smell,
very little can be added to food. You could be exposed to
small amounts of methyl mercaptan by eating foods that contain
it. However, we have no information on the levels of methyl
mercaptan in food.
You can be exposed to methyl mercaptan
if you work at a wood-pulp mill or sewage treatment plant
or if you work in a factory that uses it to make other products
such as jet fuel, pesticides, or poultry feed. Measurements
of methyl mercaptan in the air inside these mills were lower
than 4 ppm (4 parts of methyl mercaptan per million parts
of air). Methyl mercaptan has been found in the environmental
air at 4 ppb (4 parts of methyl mercaptan per billion parts
of air).
Levels of methyl mercaptan in soil are
probably very low. Even at hazardous waste sites, the levels
were about 83 ppb.
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1.3
How can methyl mercaptan enter and leave my body? |
Methyl mercaptan can enter your body
when you breathe in air or eat food that contains this chemical.
We do not know if methyl mercaptan can enter your body through
the skin or what happens to it after it enters your body,
Studies in rats suggested it leaves the body quickly. After
methyl mercaptan reaches the blood, it is either breathed
out unchanged or is broken down to other substances (within
one hour). These substances may be breathed out from the lungs
or leave the body with the urine within a few hours.
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1.4
How can methyl mercaptan affect my health? |
We have very little information on the
health effects of exposure to methyl mercaptan. A worker exposed
to very high levels (exact amount unknown) of this compound
for several days when he opened and emptied tanks of methyl
mercaptan went into a coma (became unconscious), developed
anemia (a blood disorder) and internal bleeding. He died within
a month after this incident.
We do not know whether long-term exposure
of humans to low levels of methyl mercaptan can result in
harmful health effects such as cancer, birth defects, or problems
with reproduction.
Methyl mercaptan can be smelled and recognized
in Air when it is there at a level of about 1.6 ppb (1.6 parts
of methyl mercaptan per billion parts of air). It can be smelled
when it is present in water at a level far lower than 1 ppb.
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1.5
Is there a medical test to determine whether I have been exposed
to methyl mercaptan? |
Methyl mercaptan is always present in
your body. There is a test that can be used to find out if
it is present in your blood at levels that are higher than
normal, which may happen if you are exposed to high levels
of this substance. This test requires special equipment and
is not usually available in a doctor's office. It can be done
in a special laboratory. However, this test cannot be used
to find out how much methyl mercaptan you were exposed to
or to predict whether harmful health effects will occur.
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1.6
What recommendations has the federal government made to protect
human health? |
The federal government has set certain
regulations and guidelines to help protect people from the
possible harmful health effects of methyl mercaptan in the
environment. When more than 100 pounds of methyl mercaptan
is released to the environment (such as during an industrial
accident or spill), the EPA National Response Center must
be notified. The Food and Drug Administration (FDA) allows
methyl mercaptan to be used as a food additive but does not
set specific limits on the levels that can be used. The Occupational
Safety and Health Administration (OSHA) has set an average
limit of 0.5 ppm for exposure to this chemical in workplace
air. The American Conference of Governmental Industrial Hygienists
(ACGIH) has recommended that the average concentration of
airborne methyl mercaptan should not be more than 0.5 ppm
for each 8-hour exposure (time-weighted average) in a 40-hour
work week.
The federal recommendations have been
updated as of July 1999.
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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 methyl mercaptan. Atlanta, GA: U.S. Department
of Health and HumanServices, Public Health Service.
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