Medical Management Guidelines for Mercury
(Hg)
CAS# 7439-97-6
UN# 2024 (liquid compounds)
PDF Versionpdf icon[412 KB]
Synonyms include colloidal mercury, quicksilver, liquid silver, metallic mercury, and hydrargyrum.
- Persons exposed to elemental mercury vapor do not pose a significant risk of secondary contamination to response personnel outside the Hot Zone. Persons whose skin or clothing is contaminated with liquid mercury can contaminate response personnel by direct contact or off-gassing vapor and can also contaminate equipment leading to a risk of chronic exposure for response personnel.
- Elemental mercury is a heavy, shiny, silver-white, odorless liquid. It is nonflammable, but releases toxic vapor, especially when heated. Because mercury is odorless, it does not provide any warning of hazardous concentrations.
- Inhalation is the primary route of exposure to elemental mercury vapor or aerosols, which are readily absorbed. Virtually no elemental mercury is absorbed from the gastrointestinal tract or by the skin. Mercury crosses the placenta and can be transferred to infants via breast milk.
General Information
Description
There are three classes of mercury: metallic elemental mercury (quicksilver, Hg0), inorganic mercurial salts (e.g., Hg2Cl2, Hg+, HgCl2, Hg+2), and organic mercurials (e.g., methylmercury, phenylmercury). Adverse effects from exposure to mercury differ depending on the form and the route of exposure. This Medical Management Guideline focuses on elemental mercury. At room temperature, metallic or elemental mercury is a heavy, shiny, silver-white, odorless liquid. It is only slightly volatile at room temperatures and significantly more volatile when heated. Elemental mercury is nonflammable and has low solubility in both water and organic solvents.
Routes of Exposure
Inhalation
Inhalation of mercury vapor is the primary route of exposure to elemental mercury. Inhaled vapor is almost completely absorbed by the lungs about up to 80%. Neither liquid mercury nor mercury vapor has an odor and thus, chemical odor provides no warning of hazardous concentrations. Mercury vapor is heavier than air and may therefore accumulate in poorly ventilated or low-lying areas.
Children exposed to the same levels
of mercury vapor as adults may receive larger doses because
they have greater lung surface area:body weight ratios and
increased minute volumes: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 mercury
vapor found nearer to the ground.
Skin/Eye Contact
Elemental mercury vapor is very slowly
absorbed through the skin in high concentrations, but causes irritation of both skin
and eyes and may produce contact dermatitis.
Ingestion
Elemental mercury, a liquid at room temperature,
is essentially nontoxic when ingested because virtually none
(less than 0.1%) is absorbed. Anatomic gastrointestinal abnormalities
such as enteric fistulas or intestinal perforation can sequester
sufficient quantities of ingested elemental mercury to allow
significant oxidation and subsequent absorption.
Sources/Uses
Elemental mercury is inexpensively produced
by heating mercury-containing ores and condensing the vapor.
Metallic mercury has many applications in the electrical industry
(e.g., alkaline batteries, electrical switches, lights), in
dental amalgrams, and in medical equipment (e.g., thermometers,
electroanalysis). In the chemical and mining industries, mercury
is used as a catalyst in reactions to form polymers, in manufacturing
chlorine and caustic soda, and in extracting gold from ore.
Mishandled or spilled mercury from devices used in the home
or workplace is often the source of unintentional exposures.
Standards and Guidelines
OSHA PEL (permissible exposure limit)
= 0.1 mg/m3 (vapor) (ceiling)
NIOSH IDLH (immediately dangerous to
life or health) = 10 mg/m3
Physical Properties
Description: Liquid is shiny,
silvery-white, and heavy; vapor is colorless and odorless.
Warning properties: Odor is inadequate
to warn of toxic exposure.
Molecular weight: 200.59 daltons
Boiling point (760 mm Hg): 674°F
(356.72°C)
Freezing point: -102°F (-38.9°C)
Specific gravity: 13.6 at 77°F
(25°C) (water = 1.00)
Vapor pressure: 0.002 mm Hg at
77°F (25°C)
[Note: Although the vapor pressure of elemental mercury is
low, at 24°C, an atmosphere that is fully saturated with
mercury vapor contains approximately 18 mg/m3. The levels
attainable in indoor airs at room temperature can therefore
greatly exceed safe levels and result in poisoning.]
Gas density: 6.9 (air = 1)
Water solubility: 0.006% at 77°F
(25°C)
Flammability: Nonflammable
Incompatibilities
Elemental mercury reacts vigorously with
ground mixtures of sodium carbide, aluminum, lead, or iron.
A violent exothermic reaction, possibly an explosion, occurs
when mercury comes in contact with chlorine dioxide, lithium,
or rubidium. It also reacts with acetylenic compounds, ammonia,
azides, boron diiodophosphide, ethylene oxide, methyl azide,
methylsilane, oxygen, oxidants, and tetracarbonylnickel. Pure
dry ammonia and mercury do not react even under pressure and
heat, but if water is present, a compound forms that can explode
during depressurization. Heating mercury vapor produces mercuric
oxide, which is highly irritating to mucous membranes and
more likely than elemental mercury vapor to cause chemical
pneumonitis.
Health Effects
- The major route of exposure to elemental mercury is inhalation
of mercury vapor. Symptoms of acute toxicity following high-level
exposure to mercury vapor occur within hours of the exposure.
- Respiratory symptoms include corrosive bronchitis with
fever chills and dyspnea, which can progress to pulmonary
edema or fibrosis. Abdominal cramps, diarrhea, renal dysfunction,
visual disturbances, and central nervous system damage leading
to neuropsychiatric disturbances and intention tremors may
also occur.
- Mercury vapor can cross the blood-brain and placental barriers. It is also excreted in breast milk. Children may be at increased risk for pulmonary toxicity and are more likely to develop respiratory failure.
Acute Exposure
Many acute health effects are associated
with exposure to high levels of elemental mercury vapor. Respiratory
symptoms may predominate (cough, sore throat, shortness of
breath). Gastrointestinal effects are frequent in the initial
set of symptoms (metallic taste, nausea, vomiting, diarrhea,
abdominal pain) as are CNS effects such as headache, weakness,
and visual disturbances. Several days after the initial exposure,
symptoms are more similar to those that develop following
inorganic mercury poisoning, including ptyalism (heavy salivation),
enteritis, and renal damage; there can also be chronic CNS
effects, which develop as a result of the ability of absorbed
elemental mercury to cross the blood-brain barrier.
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 exposure to high levels of elemental
mercury vapor can cause chemical pneumonitis. Within a few
hours of exposure, dyspnea, chest pain, and dry cough develop,
often associated with fever, chills, and headache. Symptoms
might resolve or gradually progress to pulmonary edema, respiratory
failure, and death.
The acute mercury-induced lung damage
usually resolves completely, but some cases of diffuse pulmonary
fibrosis, restrictive lung disease, and chronic respiratory
insufficiency have been reported. At autopsy, microscopic
examination of lung tissue reveals interstitial pneumonitis,
necrotizing bronchitis, bronchiolitis, and atelectasis.
Children may be more vulnerable to gas
exposure because of relatively increased minute ventilation
per kg and failure to evacuate an area promptly when exposed.
Renal
Acute high-dose inhalation of elemental
mercury vapor has been associated with proteinuria, nephrotic
syndrome, temporary tubular dysfunction, acute tubular necrosis,
and oliguric renal failure.
Cardiovascular
Acute inhalation of high levels of elemental
mercury vapor can cause tachycardia and hypertension. In children,
tachycardia associated with the inhalation of elemental mercury
vapor might be related to a non-allergenic hypersensitivity
reaction to mercury.
Gastrointestinal
A metallic taste, salivation, dysphagia,
abdominal cramps, diarrhea, and nausea have been reported
following inhalation of large amounts of elemental mercury
vapor. Oral and dermal exposures to elemental mercury are
not normally associated with GI symptoms.
Dermal
Dermal reactions associated with dermal
contact with liquid elemental mercury or the vapor are rare.
Acrodynia (or pink disease) is associated with hypersensitivity
to mercury absorbed from vapor inhalation or dermal exposure.
Symptoms of acrodynia include abnormal redness of the skin,
followed by peeling of skin on the hands, nose, and soles
of the feet.
CNS
Acute inhalation of mercury vapor may
produce CNS effects such as headache, weakness, and visual
disturbances.
Potential Sequelae
Respiratory effects from high-dose acute
exposures might resolve or gradually progress to adult respiratory
distress syndrome (ARDS), respiratory failure, and death.
Patients with severe pulmonary toxicity can develop interstitial
fibrosis and residual restrictive pulmonary disease. Other
sequelae of exposure to elemental mercury include effects
on the CNS and kidneys. These can occur after high-dose acute
inhalation exposure and are similar to the effects observed
following chronic lower-dose exposures (see below).
Chronic Exposure
Repeated or continuous exposure to elemental
mercury can result in accumulation of mercury in the body
and permanent damage to the nervous system and kidneys. Classic
symptoms of poisoning include neuropsychiatric effects, renal
impairment, and oropharyngeal inflammation. The neuropsychiatric
effects include tremor, anxiety, emotional lability, forgetfulness,
insomnia, anorexia, erethism (abnormal irritation, sensitivity,
or excitement), fatigue, and cognitive and motor dysfunction.
Although less common, neuromuscular changes
(weakness, muscle atrophy, and muscle twitching) and polyneuropathy
(paresthesias, stocking-glove sensory loss, hyperactive tendon
reflexes, slowed sensory and motor nerve conduction velocities)
have also been reported.
A delayed idiosyncratic non-allergic
hypersensitivity to mercury called acrodynia (pink disease)
is sometimes seen in children chronically exposed to mercury
vapor; in some cases, it occurs when exposure lasts for only
a few days. Symptoms include irritability, sleeplessness,
sweating, severe leg cramps, and a painful peeling rash.
Chronic exposure may be more serious
for children because of their potential longer latency period.
Carcinogenicity
The Department of Health and Human Services
(DHHS), the International Agency for Research on Cancer (IARC),
and the Environmental Protection Agency (EPA) have not had
sufficient evidence to classify elemental mercury as a carcinogen
or a noncarcinogen.
Reproductive and Developmental Effects
Elemental mercury 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.
Chronic inhalation of elemental mercury
vapor has not been shown to have any effect on spermatozoa
in men. An increased incidence of spontaneous abortion among
the wives of men chronically exposed to elemental mercury
has been reported.
In female workers, menstrual disorders
(dysmenorrhea) have been associated with chronic exposure
to high concentrations of mercury vapor. At high levels, inhaled
elemental mercury is able to cross the placental barrier,
but fetotoxic or significant developmental effects have not
been well studied in humans. Adverse developmental effects
have been observed in animals but not humans.
Prehospital Management
- Victims exposed to mercury vapor do not pose secondary
contamination risks to rescuers. Rescuers may treat urgently
ill patients without concern about acute secondary contamination
to themselves or their equipment.
- Victims whose skin or clothing is visibly contaminated
with liquid mercury can contaminate rescuers' equipment,
clothing, or the indoor environment. Contamination of clothing
or equipment can result in a subsequent chronic inhalation
hazard to others as the elemental liquid mercury off-gasses.
- Symptoms of acute exposure to elemental mercury vapor
inhalation occur within hours of the exposure and consist
of cough, chills, fever, and shortness of breath. Symptoms
might resolve or gradually progress to a chemical pneumonitis,
adult respiratory distress syndrome (ARDS), respiratory
failure, and renal failure. Inhalation of mercury vapor
can also cause nausea, vomiting, diarrhea, renal dysfunction,
visual disturbances, and CNS damage.
- Treatment of acute mercury exposure generally consists
of removal of the patient from further exposure followed
by support of respiratory and cardiovascular function. There
is no antidote for mercury, but chelation therapy is warranted
in some cases.
Hot Zone
Rescuers should be trained and appropriately
attired before entering the Hot Zone. If the proper equipment
is not available, or if the rescuers have not been trained
in its use, call for assistance from a local or regional HAZMAT
team or other properly equipped response organization.
Rescuer Protection
Elemental mercury vapor can be highly
toxic if inhaled and can cause a life-threatening chemical
pneumonitis and respiratory failure. Both the liquid and vapor
forms of elemental mercury are poorly absorbed through the
skin. Heating mercury vapor produces mercuric oxide, which
is highly irritating to mucous membranes and more likely than
elemental mercury vapor to cause chemical pneumonitis. Mercury
clean-up kits are available which can remove the liquid without
spreading contamination.
Respiratory Protection: Positive-pressure,
self-contained breathing apparatus (SCBA) is recommended in
response situations that involve exposure to potentially unsafe
levels of elemental mercury.
Skin Protection: No special clothing
is needed unless mercury vapor is being heated; in that case
chemical protective clothing is recommended to avoid contamination.
However, gloves and foot protection are recommended as mercury
spreads under nails etc., very easily. Any clothing that comes
in contact with liquid mercury should be properly decontaminated
or disposed of to prevent the possibility of subsequent chronic
exposure to off-gassed mercury vapor.
ABC Reminders
Quickly access for a patent airway, ensure
adequate respiration and pulse. If trauma is suspected, maintain
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 children, such as measures to reduce separation
anxiety if a child is separated from a parent or other adult.
Decontamination Zone
Victims exposed only to mercury vapor
who have no skin or eye irritation may be transferred immediately
to the Support Zone. Other patients will 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 access for 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 all personal belongings.
Wash exposed skin and hair with mild
soap and water (preferably under a shower). Rinse thoroughly
with water. Use caution to avoid hypothermia when decontaminating
children or the elderly. Use blankets or warmers when appropriate.
Flush exposed or irritated eyes with
plain water or saline for at least 5 minutes. Remove contact
lenses if easily removable without additional trauma to the
eye. If pain or injury is evident, continue irrigation while
transferring the victim to the Support Zone.
In cases of ingestion, do not induce
emesis. Elemental mercury is not readily absorbed from
the gastrointestinal tract and generally does not produce
acute toxicity from this route of exposure. Activated charcoal
is not effective for ingested mercury exposure.
Consider appropriate management of chemically
contaminated children, such as measures to reduce separation
anxiety if a child is separated from a parent or other adult.
If possible, seek assistance from a child separation expert.
Transfer to Support Zone
As soon as basic decontamination is complete,
move the victim to the Support Zone.
Support Zone
Rescuers may treat urgently ill patients
without concern about acute secondary contamination to themselves
or their equipment. However, rescuer clothing or equipment
that has been contaminated with liquid mercury can cause chronic
exposures to rescuers from off-gassed mercury vapor. Be certain
that victims have been decontaminated properly (see Decontamination
Zone above) and that any rescuer equipment or clothing
that has been contaminated with liquid mercury is properly
decontaminated or disposed of. Victims who have undergone
decontamination or have been exposed only to vapor pose no
serious risks of secondary contamination. In such cases, Support
Zone personnel require no specialized gear.
ABC Reminders
Quickly access for a patent airway. If
trauma is suspected, maintain cervical immobilization manually
and apply a cervical collar and a backboard when feasible.
Ensure adequate respiration and pulse. Administer supplemental
oxygen as required and establish intravenous access if necessary.
Place on a cardiac monitor.
Additional Decontamination
Continue irrigating exposed skin and
eyes, as appropriate.
In cases of ingestion, do not induce
emesis. Elemental mercury is not usually absorbed from
the gastrointestinal tract and does not produce acute toxicity
from this route of exposure. Activated charcoal is not effective.
Advanced Treatment
In cases of respiratory compromise secure
airway and respiration via endotracheal intubation. If not
possible, perform cricothyroidotomy if equipped and trained
to do so.
Treat patients who have bronchospasm
with aerosolized bronchodilators. The use of bronchial sensitizing
agents in situations of multiple chemical exposures may pose
additional risks. Consider the health of the myocardium before
choosing which type of bronchodilator should be administered.
Cardiac sensitizing agents may be appropriate; however, the
use of cardiac sensitizing agents after exposure to certain
chemicals may pose enhanced risk of cardiac arrhythmias (especially
in the elderly). Mercury poisoning is not known to pose additional
risk during the use of bronchial or cardiac sensitizing agents
and sympathomimetic bronchodilators may reverse bronchospasm
in patients exposed to mercury.
Consider racemic epinephrine aerosol
for children who develop stridor. Dose 0.25-0.75 mL of 2.25%
racemic epinephrine solution in 2.5 cc water, repeat every
20 minutes as needed, cautioning for myocardial variability.
Patients who are comatose, hypotensive,
or have seizures or cardiac arrhythmias should be treated
according to advanced life support (ALS) protocols.
Transport to Medical Facility
Only decontaminated patients or patients
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.
If elemental mercury has been ingested,
prepare the ambulance in case the patient vomits. The vomit
might contain elemental mercury that can contaminate the transport
vehicle. Have a suction apparatus ready and prepare several
towels and double-sealable plastic bags to quickly clean up
and isolate vomitus.
Only a professional mercury clean-up
kit with a self-contained vacuum system should be used to
decontaminate the transport vehicle. Ordinary vacuum cleaners
can vaporize elemental mercury and increase the concentration
of airborne mercury.
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
inhalation exposure such as cough, shortness of breath, nausea,
or headache and patients who have ingested large amounts of
elemental mercury should be transported to a medical facility
for evaluation. Asymptomatic patients who have not had a significant
exposure and show no evidence of respiratory-tract irritation
may be discharged from the scene after their names, addresses,
and telephone numbers are recorded. Those discharged should
be advised to seek medical care promptly if symptoms develop
(see Patient Information Sheet below).
Emergency Department Management
- Victims exposed to mercury vapor do not pose secondary
contamination risks to rescuers. Victims whose skin or clothing
is visibly contaminated with liquid mercury can contaminate
equipment, clothing, or the indoor environment by translocation
of the liquid, but do not pose a risk of acute secondary
exposure for hospital personnel.
- Contaminated clothing or equipment will subsequently pose
a chronic inhalation hazard to others as the elemental liquid
mercury off-gasses. Victims do not pose risks of secondary
contamination after their clothing is removed, the mercury
is contained, and their skin is washed.
- Symptoms of acute inhalation exposure to elemental mercury
vapor occur within hours of the exposure and consist of
coughs, chills, fever, and shortness of breath. Symptoms
might resolve or gradually progress to a chemical pneumonitis,
adult respiratory distress syndrome (ARDS), respiratory
failure, renal failure, nausea, vomiting, and diarrhea.
Exposure may also result in visual disturbances and CNS
damage.
- There is no antidote for mercury. Treatment consists of
cessation of exposure, supportive care, and timely chelation
therapy when warranted.
Decontamination Area
Previously decontaminated patients and
patients exposed only to mercury vapor who have no skin or
eye irritation may be transferred immediately to the Critical
Care Area. Others require decontamination as described below.
Be aware that use of protective equipment
by the provider may cause fear in children, resulting in decreased
compliance with further management efforts.
Because of their relatively larger surface
area:body weight ratio, children are more vulnerable to toxicants
absorbed through the skin. Also emergency room personnel should
examine children's mouths because of the frequency of hand-to-mouth
activity among children.
ABC Reminders
Evaluate and support airway, breathing,
and circulation. In cases of respiratory compromise secure
airway and respiration via endotracheal intubation. If not
possible, surgically create an airway.
Treat patients who have bronchospasm
with aerosolized bronchodilators. The use of bronchial sensitizing
agents in situations of multiple chemical exposures may pose
additional risks. Consider the health of the myocardium before
choosing which type of bronchodilator should be administered.
Cardiac sensitizing agents may be appropriate; however, the
use of cardiac sensitizing agents after exposure to certain
chemicals may pose enhanced risk of cardiac arrhythmias (especially
in the elderly). Mercury poisoning is not known to pose additional
risk during the use of bronchial or cardiac sensitizing agents.
Sympathomimetic bronchodilators may reverse bronchospasm in
patients exposed to mercury vapor.
Consider racemic epinephrine aerosol
for children who develop stridor. Dose 0.25-0.75 mL of 2.25%
racemic epinephrine solution in 2.5 cc water, repeat every
20 minutes as needed, cautioning for myocardial variability.
Patients who are comatose, hypotensive,
or have seizures or ventricular 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.
Wash exposed skin and hair with mild
soap and water (preferably under a shower). Rinse thoroughly
with water. Use caution to avoid hypothermia when decontaminating
children or the elderly. Use blankets or warmers when appropriate.
Flush exposed or irritated eyes with
plain water or saline for at least 5 minutes. Remove contact
lenses if easily removable without additional trauma to the
eye. If pain or injury is evident, continue irrigation while
transferring the victim to the Critical Care Area.
In cases of ingestion, do not induce
emesis or give activated charcoal. Elemental mercury is
not usually absorbed from the gastrointestinal tract and is
unlikely to cause any acute toxicity from this route of exposure.
Decontamination is not necessary. However, if an individual
with gastrointestinal perforation or fistula ingests an extremely
large amount, the mercury might be retained for a long period
in the GI tract and decontamination should be considered.
Cathartic whole-bowel lavage (repeated once daily) or even
surgical removal might be necessary at a later time depending
on radiographic evidence of large pockets of mercury. In cases
of large-volume ingestion, obtain an abdominal radiograph
to document the location of the mercury, and explain to the
patient the importance of follow-up. The patient should be
referred to a primary-care or specialist physician for follow-up.
If elemental mercury has been ingested
and the patient vomits, the vomitus might contain elemental
mercury that can contaminate the emergency department. Have
a suction apparatus ready and prepare several towels and double-sealable
plastic bags to quickly clean up and isolate any mercury.
If there is widespread contamination, only a professional
mercury clean-up kit with a self-contained vacuum system should
be used to decontaminate. Ordinary vacuum cleaners can vaporize
elemental mercury and increase the concentration of airborne
mercury.
Critical Care Area
Be certain that appropriate decontamination
has been carried out (see Decontamination Area above).
ABC Reminders
Evaluate and support airway, breathing,
and circulation as in ABC Reminders above. Establish
intravenous access in seriously ill patients if this has not
been done previously. Continuously monitor cardiac rhythm.
Patients who are comatose, hypotensive,
or have seizures or cardiac arrhythmias should be treated
in the conventional manner.
Fluids should be titrated to maintain
acceptable urine output and blood pressure. Care must be taken
not to overhydrate the patient.
Inhalation Exposure
Administer supplemental oxygen by mask
to patients who have respiratory complaints. Treat patients
who have bronchospasm with aerosolized bronchodilators. The
use of bronchial sensitizing agents in situations of multiple
chemical exposures may pose additional risks. Consider the
health of the myocardium before choosing which type of bronchodilator
should be administered. Cardiac sensitizing agents may be
appropriate; however, the use of cardiac sensitizing agents
after exposure to certain chemicals may pose enhanced risk
of cardiac arrhythmias (especially in the elderly). Mercury
poisoning is not known to pose additional risk during the
use of bronchial or cardiac sensitizing agents and sympathomimetic
bronchodilators may reverse bronchospasm in patients exposed
to mercury vapor.
Consider racemic epinephrine aerosol
for children who develop stridor. Dose 0.25-0.75 mL of 2.25%
racemic epinephrine solution in 2.5 cc water, repeat every
20 minutes as needed, cautioning for myocardial variability.
Young children are particularly susceptible
to the acute pulmonary effects of mercury vapor. Both adults
and children are treated by respiratory support and in some
cases, mechanical ventilation may be necessary.
Early dyspnea can indicate upper-airway
obstruction from swelling, reflex bronchospasm, or direct
pulmonary injury, which all require treatment. Patients require
careful assessment for stridor, wheezing, and rales. Patients
who have chemically induced adult respiratory distress syndrom
(ARDS) do not usually benefit from digoxin, morphine, afterload
reduction, or diuretics. Supplemental oxygen, delivered by
mechanical ventilation and positive end-expiratory pressure,
if needed, are standard treatments. Corticosteroids and antibiotics
have been commonly recommended for treatment of chemical pneumonitis,
but their effectiveness has not been substantiated.
Skin Exposure
Elemental mercury does not cause a chemical
burn. Washing the exposed skin with soap and water should
remove any residual liquid mercury.
Eye Exposure
Ensure that adequate eye irrigation has
been completed. Test visual acuity. Examine the eyes for conjunctival
or corneal damage and treat appropriately. Patients should
be referred to an ophthalmologist when they have apparent
or suspected corneal injury.
Ingestion Exposure
In cases of ingestion, do not induce
emesis or give activated charcoal. Elemental mercury is
not usually absorbed from the gastrointestinal tract and does
not produce acute toxicity from this route of exposure. Decontamination
is not necessary. However, if an individual with gastrointestinal
perforation or fistula ingests an extremely large amount,
the mercury might be retained for a long period in the GI
tract and decontamination should be considered. Mercury is
radiopaque and abdominal radiographs should be obtained in
all cases of ingestion. Cathartic whole-bowel irrigation (with
a polyethylene glycol [PEG-3350] electrolyte lavage solution,
repeated once daily) or even surgical removal might be necessary
depending on the radiographic evidence of the amount of mercury
present.
Antidotes and Other Treatments
Antidotes and Chelation therapy should
be considered for any patient with a clear history of acute
elemental mercury exposure who is symptomatic. However, the
decision to chelate for a particular patient should be made
only by professionals experienced in the use of chelation,
preferably in consultation with the regional poison control
center.
Chelation therapy becomes less effective
in reducing the severity of poisoning and the risk of sequelae
as time after exposure increases. Since timely administration
of the chelating agent is essential for its efficacy, when
treating significantly symptomatic patients, it might be necessary
to administer the chelating agent prior to laboratory confirmation
of mercury overexposure. Do not chelate an asymptomatic patient
without the guidance provided by blood and 24-hour urine mercury
levels. There may be no apparent benefit in chelating patients
with established neurotoxicity after chronic exposure.
The most frequently used agent for acute
inorganic mercury exposures is dimercaprol (also known as
BAL). BAL, however, has been found to increase brain mercury
in mice exposed to short-chain organic mercury; such an increase
could lead to increased neurotoxicity. The implications for
the use of BAL in humans are unclear, and no information is
available on the effects of BAL following exposure to inhaled
elemental mercury. Since elemental mercury has toxicokinetic
properties more similar to organic mercury than inorganic
mercury, chelation with 2,3-dimercaptosuccinic acid (DMSA)
should also be considered (see below).
The standard dosage regiment of BAL for
inorganic mercury poisoning is 3 mg/kg IM every 4 hours for
2 days, and every 12 hours thereafter for 7 to 10 days or
until 24-hour urinary excretion levels are less than 50 µg/L.
Contraindications to BAL include concurrent use of medicinal
iron (which can form a toxic complex with BAL), organic mercury
poisoning, pre-existing renal impairment, and pregnancy (except
in life-threatening circumstances). Patients often complain
of pain at the injection site. Adverse effects are dose-related
and may include: pain, a self-limited increase in heart rate
and blood pressure; nausea; vomiting; headache; burning sensation
of the lips, mouth, throat, and eyes; lacrimation; rhinorrhea;
salivation; muscle aches; burning and tingling in the extremities;
tooth pain, diaphoresis; chest pain; anxiety; and agitation.
Dimercaprol must not be administered in patients with glucose-6-phosphate
dehydrogenase deficiency, because it can produce hemolysis.
Oral agents such as 2,3-dimercaptosuccinic
acid (DMSA) or D-penicillamine have been used as alternatives
when dimercaprol toxicity or intolerance develops. DMSA has
very few side effects and is approved for the treatment of
pediatric lead poisoning in the United States. Although not
currently an FDA-labeled indication, DMSA has been used to
treat mercury poisoning and is undergoing further evaluation.
DMSA might prove to be the treatment of choice for methylmercury
because of its lower toxicity.
Other Treatments
Alkalization of the urine stabilizes
the dimercaprol-metal complex, and has been recommended to
protect the kidneys during chelation therapy. There is no
role for hemodialysis in removing mercury. However, hemodialysis
might be required for supportive therapy in the treatment
of renal failure and it might enhance the removal of the dimercaprol-mercury
complexes.
Laboratory Tests
The diagnosis of acute mercury toxicity
is partly clinical, based on symptoms of respiratory distress.
Laboratory evaluation of acute mercury poisoning should also
include a complete blood count and differential, serum electrolytes,
glucose, liver, and renal function tests, and urinalysis.
Obtain hourly intake/output and urine pH in severely ill patients
when renal perfusion is in question. Pulse oximetry might
yield insufficient information to carefully monitor impending
pneumonitis, ARDS, or respiratory failure. Chest radiography
and serial ABG measurements are recommended for severe inhalation
exposures.
Blood and urine mercury levels are useful
to confirm exposure but there is no definite correlation between
blood and urine mercury levels and degree of mercury toxicity.
Blood mercury level confirms whether the exposure was recent,
because the initial half-life for the elimination of blood
mercury is 3 days. Urinary mercury levels indicate the total
mercury body burden since mercury is largely excreted by the
kidneys. The half-life of elimination for whole body mercury
is 60 to 90 days. Urinary mercury levels are generally below
10 µg/L. Blood mercury levels are generally less than
40 µ/L and should not exceed 50 µ/L. Long-term
exposure to mercury can be estimated from levels in hair.
If large-volume ingestion (more than
the contents of a thermometer) is suspected, abdominal radiographs
should be ordered to detect and follow the transit of any
mercury (which is radiopaque) in the gastrointestinal tract.
Neuropsychiatric testing, nerve conduction studies, and urine
assays for N-acetyl-B-D-glucosaminidase and β2-microglobulin
have been used to assess delayed and chronic nervous system
and renal toxicity.
Disposition and Follow-up
Consider hospitalizing patients who have
a suspected serious exposure and/or persistent or exhibit
progressive respiratory symptoms.
Delayed Effects
Respiratory effects from high-dose exposures
might resolve or gradually progress to ARDS, respiratory failure,
and death. Infrequently, severe pulmonary effects can progress
to interstitial fibrosis and residual restrictive pulmonary
disease. Other potential sequelae of exposure to elemental
mercury include effects on the kidneys and central nervous
system. These effects can occur after high-dose acute exposure
to mercury vapor, and are similar to the effects observed
from chronic lower-dose exposures. Children under 30 months
of age are at increased risk for pulmonary toxicity and are
more susceptible to death from respiratory failure.
Patient Release
Exposed patients who are asymptomatic,
but who might have been exposed to mercury vapors, can be
discharged, but should be subsequently tested for blood or
urine mercury levels and advised about potential delayed effects.
Patients should be advised to seek medical attention promptly
if symptoms develop (see the Elemental Mercury-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 laboratory evaluation of respiratory,
gastrointestinal, renal and nervous-system status should be
arranged for severely exposed patients.
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 Appendices III and IV 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
elemental mercury.
Print this handout only.pdf icon[PDF - 31 KB]
What is elemental mercury?
Elemental mercury metal is a very heavy,
shiny, silver-white, odorless liquid at room temperature.
It is used to make many different kinds of products including
electrical switches, batteries, and medical devices such as
thermometers. It is used in industry to manufacture chlorine
and process gold ore. The body does not readily absorb liquid
mercury through the skin or stomach. However, the liquid evaporates
at room temperature, especially when heated. If inhaled, mercury
vapors can be highly toxic.
What immediate health effects can result from elemental mercury exposure?
Inhaling high concentrations of mercury
vapor can cause a cough, chills, fever, and shortness of breath,
and sometimes nausea, vomiting, and diarrhea. These symptoms
do not usually develop immediately: they might appear a few
hours after exposure. Symptoms might resolve or gradually
progress to cause serious damage to the lungs and kidneys.
Unintentional swallowing of liquid mercury usually causes
no health effects.
Can elemental mercury poisoning be treated?
Typically, low-level exposure to elemental
mercury leads to no lasting health effects and treatment is
not needed. Severely affected individuals must 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, damage to the
lungs, kidneys, and central nervous system might occur.
What tests can be done if a person has been exposed to elemental mercury?
Specific tests for the presence of mercury
in blood and urine can be useful to assess the level of exposure.
If a severe exposure has occurred, x-rays and blood and urine
tests might show whether or not the lungs and kidneys have
been damaged. Testing is not needed in every case.
Where can more information about elemental mercury be found?
If the exposure happened at work, you
might be required to contact your employer and the Occupational
Safety and Health Administration (OSHA). Employees may request
a Health Hazard Evaluation from the National Institute for
Occupational Safety and Health (NIOSH).
You can obtain more information about
mercury 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. 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 - 31 KB]
[ ] Call your doctor or the Emergency
Department if you develop any unusual signs or symptoms within
the next 24 hours, especially:
- coughing, wheezing, chest tightness, or shortness of
breath
- excessive saliva (spit)
- decreased urine or change in color
[ ] 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.