Medical Management Guidelines for Methyl Mercaptan
(CH3SH)
CAS# 74-93-1
UN# 1064
PDF Versionpdf icon[167 KB]
Synonyms include methanethiol, mercaptomethane,
thiomethanol, methyl sulfhydrate, and thiomethyl alcohol.
- Persons exposed only to methyl mercaptan pose little risk
of secondary contamination to personnel outside the Hot
Zone.
- Methyl mercaptan is a colorless flammable gas with unpleasant
odor described as rotten cabbage. It is easily ignited.
When heated to decomposition, it emits highly toxic fumes
and flammable vapors. Vapors from liquified methyl mercaptan
gas are heavier than air and may collect in low-lying areas.
Olfactory fatigue may prevent adequate warning of hazardous
concentrations.
- Methyl mercaptan is highly irritant when it contacts moist
tissues such as the eyes, skin, and upper respiratory tract.
It can also induce headache, dizziness, nausea, vomiting,
coma, and death. Ingestion of methyl mercaptan is unlikely
since it is a gas at ambient temperatures.
General Information
Description
At room temperature (above 43°F),
methyl mercaptan is a colorless gas with an unpleasant odor
described as rotten cabbage. It is slightly soluble in water.
It is generally shipped as a liquified compressed gas. When
heated to decomposition, it emits toxic fumes, such as sulfur
dioxide, and flammable vapors. Methyl mercaptan should be
stored in cool, well ventilated places. The main toxic effect
of exposure to methyl mercaptan is irritation of the respiratory
airway, skin, and eyes.
Routes of Exposure
Inhalation
Inhalation is the major route of exposure
to methyl mercaptan. An odor threshold of 0.002 ppm has been
reported for methyl mercaptan, but olfactory fatigue may occur
and thus, it may not provide adequate warning of hazardous
concentrations. Vapors of liquified methyl mercaptan gas
are heavier than air and spread along the ground. Exposure
in poorly ventilated, enclosed, or low-lying areas can result
in asphyxiation.
Children exposed to the same levels of
methyl mercaptan as adults may receive a larger dose because
they have a greater lung surface area:body weight ratios and
higher minute volume:weight ratios. In addition, they may
be exposed to higher levels than adults in the same location
because of their short stature and the higher levels of methyl
Skin/Eye Contact
Direct contact with liquid methyl mercaptan
or the gas may cause frostbite injury or irritation of the
eyes and skin.
Ingestion
Ingestion is unlikely to occur because
methyl mercaptan is a gas at room temperature.
Sources/Uses
Methyl mercaptan is produced by the reaction
of hydrogen sulfide with methanol. It is used as a gas odorant;
an intermediate in the production of pesticides, jet fuels,
and plastics; in the synthesis of methionine; and as a catalyst.
Standards and Guidelines
OSHA PEL (permissible exposure limit)
= 10 ppm (20 mg/m3)
NIOSH REL (recommended exposure limit)
= 0.5 ppm
NIOSH IDLH (immediately dangerous to
life or health) = 150 ppm
AIHA ERPG-2 (maximum airborne concentration
below which it is believed that nearly all persons could be
exposed for up to 1 hour without experiencing or developing
irreversible or other serious health effects or symptoms that
could impair their abilities to take protective action) =
25 ppm.
Physical Properties
Description: Colorless flammable
gas at room temperature
Warning properties: Odor does
not provide adequate warning of hazard
Molecular weight: 48.1 daltons
Boiling point (760 mm Hg) = 43°F
(6°C)
Freezing point: -186°F (-123°C)
Specific gravity (liquid): 0.87
at 0°C
Vapor pressure: 1,520 mm Hg at
26°C
Gas density: 1.66 (air = 1)
Water solubility: 23.3 g/L at
20°C
Flammability: flammable limits
3.9% to 21.8% at room temperature
Incompatibilities
Methyl mercaptan is incompatible with
strong oxidizers, bleaches, copper, aluminum, and nickel-copper
alloys.
Health Effects
- Methyl mercaptan gas is irritating to the eyes, skin,
and respiratory tract. Edema of the airway and lungs can
occur. Other possible effects include headache, dizziness,
tremors, and seizures, and nausea and vomiting, and lack
of coordination. The gas is rapidly absorbed in the lungs.
Skin and eye absorption are minimal; however, upon direct
contact with eyes or skin, liquified methyl mercaptan will
likely cause frostbite injury.
- Methyl mercaptan is a central nervous system depressant
that acts on the respiratory center to produce death by
respiratory paralysis.
- Individuals with pre-existing respiratory, cardiac, nervous
system, or liver impairment may be more susceptible to exposure
to methyl mercaptan.
Acute Exposure
Methyl mercaptan inhibits mitochondrial
respiration by interfering with cytochrome c oxidase. It also
inhibits several enzyme systems such as carbonic anhydrase,
beta-tyrosinase, and sodium+, potassium+ATPase. The enzyme
inhibition appears to be related to a thiol-metal interference.
Children do not always respond to chemicals
in the same way that adults do. Different protocols for managing
their care may be needed.
Respiratory
Acute inhalation exposure can irritate
the mucous membranes of the respiratory tract. This may cause
cough, dyspnea, a sensation of tightness of the chest, and
subsequent cyanosis. Respiratory depression, apnea, and pulmonary
edema were observed in animals.
Children may be more vulnerable to gas
exposure because of relatively higher minute ventilation per
kg and failure to evacuate an area promptly when exposed.
Hematologic
Severe hemolytic anemia may occur in
people with glucose-6-phosphate dehydrogenase deficiency.
Neurologic
Restlessness, headache, staggering, and
dizziness may develop; severe exposure may lead to convulsions
and coma.
Dermal
Frostbite injury can occur from contact
with the liquified gas.
Because of their relatively larger surface
area:weight ratio, children are more vulnerable to toxicants
that may affect the skin.
Ocular/Ophthalmic
High concentrations of methyl mercaptan
can cause eye irritation.
Gastrointestinal
Although ingestion is unlikely, irritation
of the mouth, throat, and esophagus are possible. Nausea and
vomiting may occur even with inhalation exposure to the gas.
Potential Sequelae
Methyl mercaptan exposure may result
in altered heme synthesis.
Chronic Exposure
Dermatitis can occur with chronic exposure
to methyl mercaptan.
Carcinogenicity
Methyl mercaptan has not been classified
for carcinogenic effects.
Reproductive and Developmental Effects
No information is available regarding
reproductive or developmental effects of methyl mercaptan
in experimental animals or humans. Methyl mercaptan is not
included in Reproductive and Developmental Toxicants,
a 1991 report published by the U.S. General Accounting Office
(GAO) that lists 30 chemicals of concern because of widely
acknowledged reproductive and developmental consequences.
Prehospital Management
- Rescue personnel are at low risk of secondary contamination
from victims who have been exposed to methyl mercaptan gas.
However, rescuers entering areas with potential high concentrations
should wear appropriate equipment to avoid selfexposure
to methyl mercaptan.
- Acute exposure to methyl mercaptan gas causes chest tightness,
coughing, and skin and eye irritation. Respiratory impairment
and noncardiogenic pulmonary edema may occur. Headache,
dizziness, and staggering gait can also occur.
- There is no specific antidote for methyl mercaptan poisoning.
Treatment is supportive of respiratory and cardiovascular
functions.
Hot Zone
Rescuers should be trained and appropriately
attired before entering the Hot Zone. If the proper equipment
is not available, or if rescuers have not been trained in
its use, assistance should be obtained from a local or regional
HAZMAT team or other properly equipped response organization.
Open flames and other ignition sources should be excluded
from areas containing methyl mercaptan gas.
Rescuer Protection
Methyl mercaptan is a central nervous
system depressant as well as respiratory-tract and skin irritant.
Vapors are well absorbed through the lungs. Skin absorption
is minimal.
Respiratory Protection: Positive-pressure,
self-contained breathing apparatus (SCBA) is recommended in
response situations that involve exposure to potentially unsafe
levels of methyl mercaptan.
Skin Protection: Chemical-protective
clothing should be worn because contact with the liquified
gas can cause skin irritation and frostbite injury.
ABC Reminders
Quickly establish a patent airway, ensure
adequate respiration and pulse. If trauma is suspected, maintain
cervical immobilization manually and apply a cervical collar
and a backboard when feasible.
Victim Removal
If victims can walk, lead them out of
the Hot Zone to the Decontamination Zone. Victims who are
unable to walk may be removed on backboards or gurneys; if
these are not available, carefully carry or drag victims to
safety.
Consider appropriate management of chemically
contaminated victims, particularly children who may suffer
separation anxiety if separated from a parent or other adult.
Decontamination Zone
Victims exposed to methyl mercaptan gas
who have no skin or eye irritation do not need decontamination.
They may be transferred immediately to the Support Zone. All
others require decontamination as described below.
Rescuer Protection
If exposure levels are determined to
be safe, decontamination may be conducted by personnel wearing
a lower level of protection than that worn in the Hot Zone
(described above).
ABC Reminders
Quickly establish a patent airway, ensure
adequate respiration and pulse. Stabilize the cervical spine
with a collar and a backboard if trauma is suspected. Administer
supplemental oxygen as required. Assist ventilation with a
bag-valve-mask device if necessary.
Basic Decontamination
Victims who are able may assist with
their own decontamination. Remove and double-bag contaminated
clothing and personal belongings.
Flush exposed skin and hair with water
for 3 to 5 minutes. Wash exposed area thoroughly with soap
and water. Use caution to avoid hypothermia when decontaminating
victims, partifularly children or the elderly. Use blankets
or warmers after decontamination as needed.
Do not irrigate eyes that have sustained
frostbite injury. Otherwise, irrigate exposed or irritated
eyes with copious amounts of tepid water for at least 15 minutes.
Eye irrigation may be carried out simultaneously with other
basic care and transport. Remove contact lenses if it can
be done without additional trauma to the eye. If pain or injury
is evident, continue irrigation while transferring the victim
to the support zone.
Consider appropriate management of chemically
contaminated children at the exposure site. Provide reassurance
to the child during decontamination, especially if separation
from a parent occurs.
Transfer to Support Zone
As soon as basic decontamination is complete,
move the victim to the Support Zone.
Support Zone
Be certain that victims have been decontaminated
properly (see Decontamination Zone above). Victims
who have undergone decontamination pose no serious risks of
secondary contamination to rescuers. In such cases, Support
Zone personnel require no specialized protective gear.
ABC Reminders
Quickly establish a patent airway and
ensure adequate respiration and pulse. If trauma is suspected,
maintain cervical immobilization manually and apply a cervical
collar and a backboard when feasible. Administer supplemental
oxygen as required and establish intravenous access if necessary.
Place on a cardiac monitor, if available. Watch for signs
of airway swelling and obstruction such as progressive hoarseness,
stridor, or cyanosis.
Additional Decontamination
Continue irrigating exposed skin and
eyes, as appropriate.
Advanced Treatment
Treat cases of respiratory compromise
with respiratory support using protocols and techniques available
and within the scope of training. Some cases may necessitate
procedures such as endotracheal intubation or cricothyrotomy
by properly trained and equipped personnel.
Treat patients who have bronchospasm
with an aerosolized bronchodilator such as albuterol.
Treat seizures with a benzodiazepine
such as diazepam. Severe hypertension may be treated according
to local protocols, although nitro prusside may be the best
choice for treating methyl mercaptan-induced hypertension.
Consider racemic epinephrine aerosol
for children who develop stridor. Dose 0.25-0.75 mL of 2.25%
racemic epinephrine solution, repeat every 20 minutes as needed.
Patients who are comatose, hypotensive,
or having seizures or who have cardiac arrhythmias should
be treated according to advanced life support (ALS) protocols.
If frostbite is present, treat by rewarming
in a water bath at a temperature of 104-108°F (40-42°C)
for 20 to 30 minutes and continue until a flush has returned
to the affected area.
Transport to Medical Facility
Only decontaminated patients or those
not requiring decontamination should be transported to a medical
facility. "Body bags" are not recommended.
Report to the base station and the receiving
medical facility the condition of the patient, treatment given,
and estimated time of arrival at the medical facility.
Multi-Casualty Triage
Consult with the base station physician
or the regional poison control center for advice regarding
triage of multiple victims.
Patients with evidence of significant
exposure (e.g., severe or persistent cough, dyspnea or chemical
burns) should be transported to a medical facility for evaluation.
Patients who have minor or transient irritation of the eyes
or throat may be discharged from the scene after their names,
addresses, and telephone numbers are recorded. They should
be advised to seek medical care promptly if symptoms develop
or recur (see Patient Information Sheet below).
Emergency Department Management
- Hospital personnel are at minimal risk of secondary contamination
from patients who have been exposed to methyl mercaptan.
However, hospital personnel in an enclosed area can be secondarily
contaminated by vapors off-gassing from heavily contaminated
clothing or skin.
- Acute exposure to methyl mercaptan causes coughing, eye
and nose irritation, lacrimation, and a burning sensation
in the chest; noncardiogenic pulmonary edema may occur.
Headache, dizziness, and staggering gait can also occur.
- Methyl mercaptan irritates the skin and eyes and can cause
burning pain and blisters. Exposure to liquefied methyl
mercaptan can result in frostbite.
- There is no specific antidote for methyl mercaptan poisoning.
Treatment consists of support of respiratory and cardiovascular
functions.
Decontamination Area
Unless previously decontaminated, all
patients with skin or eye irritation require decontamination
as described below.
Be aware that use of protective equipment
by the provider may cause anxiety, particularly in children,
resulting in decreased compliance with further management
efforts.
ABC Reminders
Evaluate and support airway, breathing,
and circulation. Treat cases of respiratory compromise with
respiratory support using protocols and techniques available
and within the scope of training. Some cases may necessitate
procedures such as endotracheal intubation or cricothyrotomy
by properly trained and equipped personnel.
Treat patients who have bronchospasm
with an aerosolized bronchodilator such as albuterol.
Treat seizures with a benzodiazepine
such as diazepam Severe hypertension may be treated according
to local protocols, although nitro prusside may be the best
choice for treating methyl mercaptan-induced hypertension.
Consider racemic epinephrine aerosol
for children who develop stridor. Dose 0.25-0.75 mL of 2.25%
racemic epinephrine solution, repeat every 20 minutes as needed.
Patients who are comatose, hypotensive,
or having seizures or cardiac arrhythmias should be treated
in the conventional manner.
Basic Decontamination
Patients who are able may assist with
their own decontamination. Remove and double bag contaminated
clothing and personal belongings.
If skin and eye contact with liquified
methyl mercaptan occurred, handle frostbite with caution.
Place frostbitten skin in warm water, 104-108°F (40-42°C).
If warm water is not available, wrap the affected part gently
in blankets. Let the circulation reestablish itself naturally.
Encourage the victim to exercise the affected part while it
is being warmed.
Flush exposed skin and hair with plain
water for no less than 15 minutes. Wash exposed area thoroughly
with soap and water. Use caution to avoid hypothermia when
decontaminating victims, particularly children or the elderly.
Use blankets or warmers after decontamination as needed.
Do not irrigate frostbitten eyes. Eye
irritation that does not involve frostbite should be irrigated
conventionally. Remove contact lenses if it can be done without
additional trauma to the eye. Continue irrigation while transporting
the patient to the Critical Care Area.
Critical Care Area
Be certain that appropriate decontamination
has been carried out.
ABC Reminders
Evaluate and support airway, breathing,
and circulation as in ABC Reminders above under Decontamination
Zone. Establish intravenous access in seriously ill patients
if this has not been done previously. Continuously monitor
cardiac rhythm, if appropriate.
Patients who are comatose, hypotensive,
or having seizures or cardiac arrhythmias should be treated
in the conventional manner.
Inhalation Exposure
Administer supplemental oxygen by mask
to patients who have respiratory symptoms. Treat patients
who have bronchospasm with an aerosolized bronchodilator such
as albuterol.
Treat seizures with a benzodiazepine
such as diazepam. Severe hypertension may be treated according
to local protocols, although nitro prusside may be the best
choice for treating methyl mercaptan-induced hypertension.
Consider racemic epinephrine aerosol
for children who develop stridor. Dose 0.25-0.75 mL of 2.25%
racemic epinephrine solution, repeat every 20 minutes as needed.
If pulmonary edema develops, maintain
ventilation and oxygenation and evaluate with frequent arterial
blood gas or pulse oximetry monitoring. Early use of PEEP
and mechanical ventilation may be needed. Prophylactic antibiotic
therapy may reduce the chances of respiratory infection.
Skin Exposure
If the skin was in contact with methyl
mercaptan, thermal burns may occur. Treat thermal burns by
assuring that affected area is cool by flushing with cool
water, then apply dry sterile dressings.
If the liquefied methyl mercaptan gas
contacts the skin, frostbite may result. If a victim has frostbite,
treat by rewarming affected areas in a water bath at a temperature
of 104-108
°F (40-42
°C) for 20 to 30 minutes and
continue until a flush has returned to the affected area.
Eye Exposure
Exposed eyes should be irrigated for
at least 15 minutes. Test visual acuity and examine the eyes
for corneal damage and treat appropriately. Immediately consult
an ophthalmologist for patients who have corneal injuries.
Antidotes and Other Treatments
There is no specific antidote for methyl
mercaptan. Treatment is supportive.
Laboratory Tests
The diagnosis of acute methyl mercaptan
toxicity is primarily clinical, based on respiratory difficulties
and irritation. However, laboratory testing is useful for
monitoring the patient and evaluating complications. Routine
laboratory studies for all exposed patients include CBC, glucose,
and electrolyte determinations. Patients who have respiratory
complaints require pulse oximetry (or ABG measurements) and
chest radiography. Massive inhalation may be complicated by
hyperchloremic metabolic acidosis; in addition to electrolytes,
monitor blood pH.
Disposition and Follow-up
Consider hospitalizing patients who have
a suspected significant exposure or have eye burns or serious
skin burns.
Delayed Effects
Symptomatic patients complaining of persistent
shortness of breath, severe cough, or chest tightness should
be admitted to the hospital and observed until symptom-free.
Pulmonary injury may progress for several hours.
Patient Release
Asymptomatic patients and those who experienced
only minor sensations of burning of the nose, throat, eyes,
and respiratory tract (with perhaps a slight cough) may be
released. In most cases, these patients will be free of symptoms
in an hour or less. They should be advised to seek medical
care promptly if symptoms develop or recur (see the Methyl
Mercaptan--Patient Information Sheet below).
Follow-up
Obtain the name of the patient's primary
care physician so that the hospital can send a copy of the
ED visit to the patient's doctor.
Follow up is recommended for all hospitalized
patients because long-term respiratory problems can result.
Respiratory monitoring is recommended until the patient is
symptom-free.
Patients who have skin or corneal injury
should be re-examined within 24 hours. Anyone who had significant
dermal exposure should be followed for several months.
Reporting
If a work-related incident has occurred,
you may be legally required to file a report; contact your
state or local health department.
Other persons may still be at risk in
the setting where this incident occurred. If the incident
occurred in the workplace, discussing it with company personnel
may prevent future incidents. If a public health risk exists,
notify your state or local health department or other responsible
public agency. When appropriate, inform patients that they
may request an evaluation of their workplace from OSHA or
NIOSH. See Appendix III for a list of agencies that may be
of assistance
Patient Information Sheet
This handout provides information and
follow-up instructions for persons who have been exposed to
methyl mercaptan.
Print this handout only.pdf icon[PDF - 45.5 KB]
What is methyl mercaptan?
Methyl mercaptan is a flammable colorless
gas with unpleasant odor described as rotten cabbage. It is
used as a gas odorant; an intermediate in the production of
pesticides, jet fuels, and plastics; and in the synthesis
of the amino acid methionine. Because methyl mercaptan is
a gas a ambient temperature, the most likely exposure routes
are inhalation and dermal.
What immediate health effects can be caused by exposure to methyl mercaptan?
Exposure to methyl mercaptan may cause
immediate irritation of the eyes, nose, and throat, and shortness
of breath, as well as coughing, wheezing, shortness of breath,
and tearing of the eyes. Exposure to methyl mercaptan can
also cause nausea and vomiting and dizziness, headache, and
lack of coordination. Generally, the more serious the exposure,
the more severe the symptoms.
Can methyl mercaptan poisoning be treated?
There is no antidote for methyl mercaptan,
but its effects can be treated and most exposed persons get
well. Persons who have experienced serious symptoms may need
to be hospitalized.
Are any future health effects likely to occur?
A single small exposure from which a
person recovers quickly is not likely to cause delayed or
long-term effects. After a serious exposure, symptoms may
worsen for several hours and respiratory effects may persist
for hours or days following exposure.
What tests can be done if a person has been exposed to methyl mercaptan?
Methyl mercaptan is normally present
in human blood and urine. Detection of abnormally high levels
of methyl mercaptan in the blood may be an indication of recent
exposure. However, blood tests do not indicate the extent
or time of exposure. Specific tests for the presence of methyl
mercaptan in the blood or urine are, therefore, not generally
useful to the doctor. If a severe exposure has occurred, blood
and urine analyses and other tests may show whether the upper
respiratory airways and lungs or brain have been injured.
Testing is not needed in every case.
Where can more information about methyl mercaptan be found?
More information about methyl mercaptan
can be obtained from your regional poison control center,
your state, county, or local health department; the Agency
for Toxic Substances and Disease Registry (ATSDR); your doctor;
or a clinic in your area that specializes in occupational
and environmental health. If the exposure happened at work,
you may wish to discuss it with your employer, the Occupational
Safety and Health Administration (OSHA), or the National Institute
for Occupational Safety and Health (NIOSH). Ask the person
who gave you this form for help in locating these telephone
numbers.
Follow-up Instructions
Keep this page and take it with you to
your next appointment. Follow only the instructions
checked below.
Print this handout only.pdf icon[PDF - 45.5 KB]
[ ] Call your doctor or the Emergency
Department if you develop any unusual signs or symptoms within
the next 24 hours, especially:
- coughing or wheezing
- difficulty breathing, shortness of breath, or chest pain
- increased pain or a discharge from injured eyes
- increased redness or pain or a pus-like discharge in the
area of a skin burn
- headache, dizziness, or lack of coordination
[ ] No follow-up appointment is necessary
unless you develop any of the symptoms listed above.
[ ] Call for an appointment with Dr.____
in the practice of ________.
When you call for your appointment, please
say that you were treated in the Emergency Department at _________
Hospital by________and were advised to be seen again in ____days.
[ ] Return to the Emergency Department/Clinic
on ____ (date) at _____ AM/PM for a follow-up examination.
[ ] Do not perform vigorous physical
activities for 1 to 2 days.
[ ] You may resume everyday activities
including driving and operating machinery.
[ ] Do not return to work for _____days.
[ ] You may return to work on a limited
basis. See instructions below.
[ ] Avoid exposure to cigarette smoke
for 72 hours; smoke may worsen the condition of your lungs.
[ ] Avoid drinking alcoholic beverages
for at least 24 hours; alcohol may worsen injury to your stomach
or have other effects.
[ ] Avoid taking the following medications:
________________
[ ] You may continue taking the following
medication(s) that your doctor(s) prescribed for you: _______________________________
[ ] Other instructions:
____________________________________
_____________________________________________________
- Provide the Emergency Department with the name and the
number of your primary care physician so that the ED can
send him or her a record of your emergency department visit.
- You or your physician can get more information on the
chemical by contacting: ____________ or _____________, or by
checking out the following Internet Web sites:
___________;__________.
Signature of patient _______________ Date ____________
Signature of physician _____________ Date ____________
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.