Medical Management Guidelines for Malathion
(C10H19O6PS2)
CAS# 121-75-5
UN# 2783
PDF Versionpdf icon[73.2 KB]
Synonyms include S-[1,2-Di(ethoxycarbonyl)ethyl]O,
O-dimethyl-phosphorothioate, diethyl (dimethoxyphosphinothioylthio)
succinate, and a variety of trade names such as Cekumal, Cythion,
Fosfothion, Fyfafon, Malixol, Maltox, Sadophos, and Zithiol.
- Persons whose skin or clothing is contaminated with liquid
or powdered malathion can cause secondary contamination
by direct contact.
- Malathion is an organophosphate pesticide. At room temperature,
it is a combustible yellow to deep brown liquid that may
be difficult to ignite. In commercial products, malathion
is usually dissolved in hydrocarbon solvents such as toluene
or xylene, which are flammable. Malathion has a garlic-like
odor, which does not provide adequate warning of hazardous
concentrations.
- Because malathion has a low vapor pressure, significant
inhalation is unlikely at ordinary temperatures. However,
the hydrocarbon solvents in commercial preparations can
be inhaled. Malathion is rapidly absorbed by ingestion and
through intact skin and the eyes, resulting in acute systemic
toxicity.
General Information
Description
At room temperature, malathion is a yellow
to deep brown liquid with an odor of garlic. It is a solid
below 37ºF. It is often dissolved in a hydrocarbon solvent
before use. Malathion itself is not volatile. It is slightly
soluble in water, soluble in alcohols and aromatic solvents,
and of limited solubility in petroleum oils. The premium grade
can maintain its biological activity unchanged for approximately
2 years if stored unopened in a cool, shaded, and well aired
place at 68-86ºF.
Routes of Exposure
Inhalation
Inhalation is not a significant route
of exposure to malathion at ordinary temperatures because
of its low volatility, but toxic effects can occur after inhalation
of malathion sprays or dusts. The hydrocarbon solvents (most
commonly toluene and xylene) used to dissolve malathion are
more volatile than malathion itself, and toxicity can result
from inhalation of solvent vapor as well. The odor threshold
of malathion is very close (13.5 mg/m³) to the OSHA PEL
(15 mg/m³) and may not provide adequate warning of
hazardous concentrations.
Children exposed to the same levels of
malathion as adults may receive a larger dose because they
have greater lung surface area:body weight ratios and higher
minute volume:weight ratios.
Skin/Eye Contact
Dermal exposure constitutes a major route
of exposure during and following malathion application to
fields and following aerial spraying for pest control and
residential use. Malathion is irritating to the skin and eyes,
and is readily absorbed through intact skin, contributing
to systemic toxicity.
Because of their relatively larger surface
area:weight ratio, children are more vulnerable to toxicants
absorbed through the skin.
Ingestion
Malathion residues are often detected
in foods but this level of exposure is not of concern. Acute
toxic effects, including rapidly fatal systemic poisoning,
can result from ingestion of high amounts of malathion.
Sources/Uses
Malathion is produced by the reaction
of phosphorus pentasulfide with methanol in toluene to produce
an intermediate, dimethylphosphorodithioic acid. The intermediate
is isolated and then reacted with either diethylfumarate or
diethylmaleate. Malathion is widely used as an agricultural
insecticide. It is used to kill insects on agricultural crops,
on stored products, on golf courses, and in home gardens.
It also used to kill mosquitoes and fruit flies in large outdoor
areas. In addition, it is used to kill fleas on pets and to
treat head lice on humans.
Standards and Guidelines
OSHA PEL (permissible exposure limit)
= 15 mg/m³ (skin) (averaged over an 8-hour workshift)
NIOSH REL-TWA (recommended exposure limit)
= 10 mg/m³ (skin)
NIOSH IDLH (immediately dangerous to
life or health) = 250 mg/m³
Physical Properties
Description: Yellow to deep brown
liquid at room temperature
Warning properties: Garlic odor
at 13.5 mg/m³; inadequate warning for acute and chronic
exposures. May produce skin irritation
Molecular weight: 330.36 daltons
Boiling point (0.7 torr): 156-157ºC
Freezing point: 37.2ºF (2.9ºC)
Specific gravity: 1.23 (water
= 1)
Vapor pressure: 5 x 10-6 mm Hg
at 25ºC
Water solubility: 145 mg/L at
20ºC
Flammability: >325ºF
Incompatibilities
Malathion reacts with strong oxidizers,
magnesium and alkaline pesticides.
Health Effects
- Systemic malathion toxicity due to excess cholinergic
stimulation may result from all routes of exposure. Symptoms
include abdominal cramps, vomiting, diarrhea, pinpoint pupils
and blurred vision, excessive sweating, salivation and lacrimation,
wheezing, excessive tracheobronchial secretions, agitation,
seizures, bradycardia or tachycardia, muscle twitching and
weakness, and urinary and fecal incontinence. Seizures are
much more common in children than in adults.
- Death results from loss of consciousness, coma, excessive
bronchial secretions, respiratory depression and cardiac
irregularity.
- Commercial malathion products often contain impurities
and hydrocarbon solvents, such as xylene or toluene, which
themselves can cause toxicity.
- Toxicity of malathion depends on metabolic activation;
thus, symptoms may appear from a few minutes to a few hours
after exposure.
Acute Exposure
Malathion, like all organophosphate pesticides,
inhibits acetylcholinesterase and alters cholinergic synaptic
transmission at neuroeffector junctions (muscarinic effects),
at skeletal myoneural junctions and autonomic ganglia (nicotinic
effects), and in the central nervous system. Inhibition occurs
when malaoxon, a metabolite of malathion, binds to acetylcholinesterase;
thus, symptoms may be delayed after exposure. Signs and symptoms
of poisoning vary according to age, dose, and concentration.
Most systemic effects are secondary to inhibition of acetylcholinesterase.
Muscarinic effects include pinpoint pupils;
blurred vision; hypersecretion by salivary, lacrimal, sweat,
and bronchial glands; narrowing of the bronchi; nausea, vomiting,
diarrhea, and crampy abdominal pains; urinary and fecal incontinence;
and slow heart rate.
Nicotinic effects include muscle twitching,
cramping, and weakness. Nicotinic stimulation can obscure
certain muscarinic effects and produce rapid heart rate and
high blood pressure.
CNS
CNS effects are often the earliest manifestations
of poisoning in adults and constitute the major signs and
symptoms in children. CNS effects include irritability, nervousness,
giddiness, fatigue, lethargy, impairment of memory, confusion,
slurred speech, visual disturbance, depression, impaired gait,
convulsions, loss of consciousness, coma, and respiratory
depression.
Peripheral Neurologic
Peripheral neurologic effects include
muscle twitching and weakness due to inhibition of acetylcholinesterase
at neuromuscular junctions.
Respiratory
Respiratory failure is the most common
cause of death due to malathion poisoning. Narrowing of the
bronchi and markedly increased bronchial secretions can occur.
Respiratory failure results from respiratory depression coupled
with paralysis of the respiratory muscles and progressive
airway obstruction from bronchorrhea. In addition, pulmonary
aspiration of the hydrocarbon solvents found in many commercial
preparations can cause inflammation of the lungs.
Children may be more vulnerable because
of relatively higher minute ventilation per kg and failure
to evacuate an area promptly when exposed.
Cardiovascular
Most exposure victims experience bradycardia,
but pulse rate may be increased initially and tachycardia
is more common in very severe poisoning. Irregular heartbeat
may occur.
Gastrointestinal
Nausea, vomiting, abdominal cramps, diarrhea,
and fecal incontinence are common manifestations, regardless
of the exposure route. These are generally the earliest symptoms
to occur.
Dermal
Malathion is has been reported to cause
skin irritation and sensitization. Because it is readily absorbed
through the skin, skin contact can result in systemic poisoning.
Because of their relatively larger surface
area:body weight ratio, children are more vulnerable to toxicants
absorbed through the skin.
Ocular/Ophthalmic
Systemic poisoning typically causes pinpoint
pupils and spasm of the muscle of visual accommodation (i.e.,
ciliary muscle) leading to blurred vision and aching pain
in the eye. However, organophosphate poisoning may still be
present without pinpoint pupils, and dilation of the pupils
may even be noted occasionally. Eye irritation, if it occurs,
is most likely caused by the hydrocarbon solvents used in
commercial pesticide preparations.
Potential Sequelae
Complete recovery generally occurs within
10 days unless severe lack of oxygen has caused residual brain
damage. CNS effects such as confusion, fatigue, irritability,
nervousness, and impairment of memory can occasionally last
for several weeks. There is no evidence that malathion induces
delayed neurotoxicity.
Chronic Exposure
Persistent weakness and impaired memory
have been reported to occur from low-level exposures to some
organophosphates in the absence of acute cholinergic effects,
but there is no reliable information on adverse health effects
of chronic exposure to malathion.
Carcinogenicity
The International Agency for Research
on Cancer has determined that malathion is unclassifiable
as to its carcinogenicity to humans. In animals, malathion
induced liver carcinogenicity at doses that were considered
excessive.
Reproductive and Developmental Effects
Studies have been reported in which malathion
induced transient testicular effects in rodents. Results from
studies addressing reproductive or developmental effects in
humans are inconclusive. Malathion is not included in Reproductive
and Developmental Toxicants, a 1991 report published by
the U.S. General Accounting Office (GAO) that lists 30 other
chemicals of concern because of widely acknowledged reproductive
and developmental consequences.
Prehospital Management
- Malathion is highly contaminating. Victims whose skin
or clothing is contaminated with liquid or powdered malathion
can secondarily contaminate response personnel by direct
contact or evaporation of solvent vapor. Clothing and leather
goods (e.g., belts or shoes) cannot be reliably decontaminated;
they should be incinerated.
- Systemic effects of malathion poisoning can occur from
all routes of exposure. Symptoms of malathion poisoning
can include headache, nausea, vomiting, abdominal cramps,
diarrhea, generalized muscle weakness and twitching, slurred
speech, pinpoint pupils, excessive secretions, and shortness
of breath.
- Severely poisoned patients may develop seizures, skeletal-muscle
paralysis, cardiac arrhythmias, and respiratory failure,
or may become comatose.
- Commercial malathion products often contain hydrocarbon
solvents, such as xylene or toluene, which themselves can
cause toxicity. Treatment for breathing the solvent is fresh
air.
- Treatment for malathion poisoning consists of thorough
decontamination, cardiorespiratory support, and administration
of the antidotes atropine and pralidoxime. In cases of severe
poisoning, diazepam should also be administered. Antidotes
should be administered as prevention even if the diagnosis
is in doubt.
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.
Rescuer Protection
Malathion is a systemic poison that is
absorbed well by all routes of exposure.
Respiratory Protection: Positive-pressure,
self-contained breathing apparatus (SCBA) is recommended in
response situations that involve exposure to potentially unsafe
levels of malathion as may occur in large spills or contamination
in confined spaces.
Skin Protection: Chemical-protective
clothing is recommended because malathion is rapidly absorbed
through the skin and may cause systemic poisoning.
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 in victims
with chemically-induced acute disorders, especially children
who may suffer separation anxiety if separated from a parent
or other adult.
Decontamination Zone
All victims suspected of malathion ingestion,
or substantial exposure to aerosolized malathion, or who have
skin or eye exposure to liquid or powdered malathion require
thorough 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
Rapid and thorough decontamination
is critical, but must proceed concurrently with supportive
and antidotal measures.
Victims who are able may assist with
their own decontamination. Quickly remove and double-bag contaminated
clothing and personal belongings. Clothing (especially leather
items) is extremely difficult to decontaminate; in most cases,
contaminated clothing should be incinerated as directed by
hazardous materials experts.
Victims should be washed repeatedly with
copious amounts of soap and water. Rescuers should wear rubber
gloves as vinyl gloves provide no protection against skin
absorption. It is important to observe the patient closely
for sudden appearance of symptoms. It is important to thoroughly
clean hair, fingernails, and skin folds. Use caution to avoid
hypothermia when decontaminating victims, particularly children
or the elderly. Use blankets or warmers after decontamination
as needed.
Irrigate exposed or irritated eyes with
plain water or saline for 15 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. If the victim is alert and asymptomatic, administer
a slurry of activated charcoal at a dose of 1 g/kg (infant,
child, and adult dose). A soda can and straw may be of assistance
when offering charcoal to a child. 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 or have been exposed only
to vapor generally pose no serious risks of secondary contamination
to rescuers. However, the Support Zone team should wear disposable
aprons or gowns and rubber gloves for protection.
ABC Reminders
Quickly establish 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, if available. Airway suctioning
may be required for excessive bronchial secretions.
Additional Decontamination
Continue irrigating exposed skin and
eyes, as appropriate.
In cases of ingestion, do not induce
emesis. If the victim is alert and asymptomatic, administer
a slurry of activated charcoal if it has not already been
given at a dose of 1 g/kg (infant, child, and adult dose).
A soda can and straw may be of assistance when offering charcoal
to a child.
Advanced Treatment
Treat cases of respiratory compromise,
coma, or excessive pulmonary secretions 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.
When possible, atropine (see Antidotes,
below) should be given under medical supervision to all symptomatic
patients who have known or strongly suspected malathion poisoning.
Patients who are comatose, hypotensive,
or having seizures or cardiac arrhythmias should be treated
according to advanced life support (ALS) protocols.
Antidotes
Two antidotes are administered to treat
organophosphate poisoning. Atropine is a competitive antagonist
of acetylcholine at muscarinic receptors and is used to control
the excessive bronchial secretions which are often responsible
for death. Pralidoxime relieves both the nicotinic and muscarine
effects of organophosphate poisoning by regenerating acetylcholinesterase
and can reduce both the bronchial secretions and the muscle
weakness associated with poisoning.
The initial intravenous dose of atropine
in adults should be determined by the severity of symptoms:
An initial adult dose of 1.0 to 2.0 mg or pediatric dose of
0.01 mg/kg (minimum 0.01 mg) should be administered intravenously.
If intravenous access cannot be established, atropine may
also be given intramuscularly, subcutaneously or via endotracheal
tube. Doses should be repeated every 15 minutes until excessive
secretions and sweating have been controlled. Once bronchial
secretion has been controlled, atropine administration should
be repeated whenever the secretions begin to recur. In seriously
poisoned patients, very large doses may be required. Alterations
of pulse rate and pupillary size should not be used as indicators
of treatment adequacy.
Pralidoxime should be administered as
early in poisoning as possible as its efficacy may diminish
when given more than 24 to 36 hours after exposure. Doses
are as follows: adult 1.0 g; pediatric 25 to 50 mg/kg. The
drug should be administered intravenously over 30 to 60 minutes,
but in a life-threatening situation, one-half of the total
dose can be given per minute for a total administration time
of 2 minutes. Treatment should begin to take effect within
40 minutes with a reduction in symptoms and the amount of
atropine necessary to control bronchial secretion. The initial
dose can be repeated in 1 hour and then every 8 to 12 hours
until the patient is clinically well and no longer requires
atropine. If intravenous access cannot be established, pralidoxime
may also be given intramuscularly.
Early administration of diazepam in addition
to the combined atropine and pralidoxime treatment may help
prevent the onset of seizures and potential brain and cardiac
morphologic damage following high-level organophosphate poisoning.
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. Severely
ill patients should be taken to a medical facility immediately.
If malathion has been ingested, prepare
the ambulance in case the victim vomits toxic material. Have
ready several towels and open plastic bags to quickly clean
up and isolate vomitus.
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, such as nausea or excessive sweating, and all persons
who have ingested malathion should be transported to a medical
facility for evaluation. Others may be discharged at the scene
after their names, addresses, and telephone numbers are recorded.
It is very important to ensure that individuals have been
completely decontaminated before discharge; otherwise life-threatening
symptoms may occur in the absence of assistance. Those discharged
should be advised to seek medical care promptly if symptoms
develop (see Patient Information Sheet below).
Emergency Department Management
- Malathion is highly contaminating. Patients whose skin
or clothing is contaminated with liquid or powdered malathion
can secondarily contaminate hospital personnel by direct
contact or off-gassing of solvent vapor from clothing, skin,
or vomitus. Clothing and leather goods (e.g., belts or shoes)
cannot be reliably decontaminated; they should be incinerated.
- Systemic malathion toxicity due to excess cholinergic
stimulation may be expressed in symptoms such as headache,
nausea, vomiting, abdominal cramps, diarrhea, generalized
muscle weakness and twitching, slurred speech, pinpoint
pupils, excessive secretions, and shortness of breath.
- Severely poisoned patients may develop seizures, skeletal-muscle
paralysis, cardiac arrhythmias and respiratory failure,
or may become comatose.
- Commercial malathion products often contain hydrocarbon
solvents such as xylene or toluene, which themselves can
cause toxicity.
- Treatment consists of thorough decontamination, cardiorespiratory
support, and administration of the antidotes atropine and
pralidoxime. Antidotes should be administered as prevention
even if the diagnosis is in doubt.
Decontamination Area
Unless decontaminated previously, all
patients suspected of skin or eye contact with liquid or powdered
malathion require decontamination immediately. If a solvent
such as xylene or toluene is involved, decontamination should
take place outdoors or with proper ventilation.
Health care personnel should don butyl
rubber aprons and butyl rubber gloves. If butyl rubber items
are not available, limited protection will be provided by
two layers of latex gloves and a waterproof apron or chemical-resistant
jumpsuit. Wash hands frequently during decontamination and
promptly dispose of latex gloves. Personnel who come in contact
with malathion secondarily should undergo decontamination.
Be aware that use of protective equipment
by the provider may cause anxiety, particularly 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, coma,
or to facilitate tracheal suctioning, secure airway and respiration
via endotracheal intubation. If not possible, surgically create
an airway. Suctioning may be required for excessive bronchial
secretions.
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. Dispose of contaminated
clothing and leather goods (e.g., belts, wallets, and shoes);
they should be incinerated as directed by hazardous materials
experts.
Victims should be washed repeatedly with
copious amounts of soap and water. Rescuers should wear rubber
gloves as vinyl gloves provide no protection against skin
absorption. It is important to observe the patient closely
for sudden appearance of symptoms. It is important to thoroughly
clean hair, fingernails, and skin folds. Use caution to avoid
hypothermia when decontaminating victims, particularly children
or the elderly. Use blankets or warmers after decontamination
as needed.
Flush exposed eyes with plain water or
saline for 15 minutes. Remove contact lenses if easily removable
without additional trauma to the eye. Continue irrigation
during transport to the Critical Care Area.
In cases of ingestion, do not induce
emesis. If the victim is alert and asymptomatic, administer
a slurry of activated charcoal if it has not already been
given at a dose of 1 g/kg (infant, child, and adult dose).
A soda can and straw may be of assistance when offering charcoal
to a child.
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. Continuously monitor cardiac
rhythm.
Patients who are comatose, hypotensive,
or have seizures or cardiac arrhythmias should be treated
in the conventional manner.
Inhalation Exposure
Administer supplemental oxygen by mask
to patients who have respiratory symptoms. Refer to Antidotes
and Other Treatments below for appropriate clinical treatment.
Skin Exposure
Malathion may irritate the skin and dermal
exposure produces systemic toxicity. Thorough washing of the
skin, as described in Basic Decontamination above,
should be performed and may need to be repeated. Unexplained,
persistent symptoms may indicate inadequate decontamination.
Because of their relatively larger surface
area:body weight ratio, children are more vulnerable to toxicants
absorbed through the skin.
Eye Exposure
Continue irrigation for at least 15 minutes.
Test visual acuity. Examine the eyes for cornea1 damage and
treat appropriately. Immediately consult an ophthalmologist
for patients who have severe corneal injuries.
Ingestion
Do not induce emesis. If the victim
is alert and asymptomatic, administer a slurry of activated
charcoal if it has not already been given at a dose of 1 g/kg
(infant, child, and adult dose). A soda can and straw may
be of assistance when offering charcoal to a child.
Gastric lavage is useful in certain circumstances
to remove toxic material. Consider gastric lavage with a small
nasogastric tube if: (1) a large dose has been ingested; (2) the
patient's condition is evaluated within 30 minutes; (3) the
patient has oral lesions or persistent esophageal discomfort;
and (4) the lavage can be administered within one hour of
ingestion. Care must be taken when placing the gastric tube
because blind gastric-tube placement may further injure the
chemically damaged esophagus or stomach.
Because children do not ingest large
amounts of toxic materials, and because of the risk of perforation
from NG intubation, lavage is discouraged in children unless
performed under endoscopic guidance.
Toxic vomitus or gastric washings should
be isolated, e.g., by attaching the lavage tube to isolated
wall suction or another closed container.
Antidotes and Other Treatments
All patients who have signs or symptoms
of systemic toxicity require antidotal treatment. In the United
States, primary antidotal treatment for malathion poisoning
involves administration of atropine. In addition, pralidoxime
(2-PAM) is indicated for seriously poisoned patients.
Atropine is a competitive antagonist
of acetylcholine at muscarinic receptors and is used to control
the excessive bronchial secretions which are often responsible
for death. Pralidoxime relieves both the nicotinic and muscarine
effects of organophosphate poisoning by regenerating acetylcholinesterase
and can reduce both the bronchial secretions and the muscle
weakness associated with poisoning.
The initial intravenous dose of atropine
in adults should be determined by the severity of symptoms:
An initial adult dose of 1.0 to 2.0 mg or pediatric dose of
0.01 mg/kg (minimum 0.01 mg) should be administered intravenously.
If intravenous access cannot be established, atropine may
also be given intramuscularly, subcutaneously, or via endotracheal
tube. Doses should be repeated every 15 minutes until excessive
secretions and sweating have been controlled. Once bronchial
secretion has been controlled, atropine administration should
be repeated whenever the secretions begin to recur. In seriously
poisoned patients, very large doses may be required. Alterations
of pulse rate and pupillary size should not be used as indicators
of treatment adequacy.
Pralidoxime should be administered as
early in poisoning as possible as its efficacy may diminish
when given more than 24 to 36 hours after exposure. Doses
are as follows: adult 1.0 g; pediatric 25 to 50 mg/kg. The
drug should be administered intravenously over 30 to 60 minutes,
but in a life-threatening situation, one-half of the total
dose can be given per minute for a total administration time
of 2 minutes. Treatment should begin to take effect within
40 minutes with a reduction in symptoms and the amount of
atropine necessary to control bronchial secretion. The initial
dose can be repeated in 1 hour and then every 8 to 12 hours
until the patient is clinically well and no longer requires
atropine. If intravenous access cannot be established, pralidoxime
may also be given intramuscularly.
Early administration of diazepam in addition
to the combined atropine and pralidoxime treatment may help
prevent the onset of seizures and potential brain and cardiac
morphologic damage following high-level organophosphate poisoning.
Treat patients in seizure with a benzodiazepine such as diazepam
or lorazepam.
Avoid other acetylcholinesterase inhibitors
(e.g., physostigmine and edrophonium chloride), and do not
use depolarizing neuromuscular blockers such as succinylcholine
for rapid sequence intubation. The paralyzing effects
of succinylcholine are likely to be prolonged because it will
not be metabolized normally.
Non-depolarizing neuromuscular blockers
(e.g., pancuronium and vecuronium) may be less effective because
of unsuccessful competition with acetylcholinesterase for
the motor end-plate receptors.
Laboratory Tests
The diagnosis of acute malathion toxicity
is primarily clinical and is based on the combination of nausea,
excessive sweating and salivation, miosis, and muscle weakness.
Routine laboratory studies for all exposed patients include
CBC, glucose, and electrolyte determinations. A chest radiograph
is useful to examine for hydrocarbon aspiration and non-cardiogenic
pulmonary edema. Symptomatic and asymptomatic patients suspected
of significant exposure should have determinations of plasma
and red blood cell (RBC) cholinesterase activity. Symptoms
of acute poisoning are usually present when more than 50%
of RBC cholinesterase activity is inhibited. However, these
tests are not always readily available and are more useful
in diagnosis and follow-up. Blood and urine analyses for the
presence of malathion or its metabolite may indicate recent
exposure to malathion. High levels in the blood or urine may
be indicative of potential for brain, heart, lung, and nerve
damage.
Disposition and Follow-up
Patients with life threatening illness
must be hospitalized, also consider hospitalizing patients
who have a suspected serious exposure and are symptomatic.
Delayed Effects
Skin absorption can cause delayed or
recurrent symptoms. Contaminated clothing and leather items
(e.g., shoes, wallets, and belts) should not be reused, even
if they have been washed.
Aspiration of commercial malathion preparations
that contain hydrocarbon solvents can result in chemical pneumonitis.
Chronic neurologic symptoms have been
reported for some patients exposed to some organophosphates,
but not specifically for malathion.
Patient Release
Patients who remain asymptomatic for
4 to 6 hours after exposure may be discharged with instructions
to seek medical care promptly if symptoms develop (see Malathion--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.
Patients who have severe exposure should
be evaluated for persistent CNS sequelae.
Patients who have been acutely poisoned
should be advised to avoid further organophosphate exposure
until sequential RBC cholinesterase levels have stabilized
in the normal range, a process that may take 3 to 4 months
after severe poisoning.
Patients who have corneal injuries or
severe skin burns should be reexamined within 24 hours.
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
malathion.
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What is malathion?
Malathion is an organophosphate pesticide.
It is a yellow to deep brown liquid with an odor like garlic.
It is widely used to kill insects on agricultural crops, on
stored products, on golf courses, and in home gardens. It
also used to kill mosquitoes and fruit flies in large outdoor
areas. In addition, it is used to kill fleas on pets and to
treat head lice on humans, and by farmers as a pesticide on
fruits, vegetables, nuts, and grains. Commercial pesticides
often contain a hydrocarbon solvent, which itself can cause
illness.
What immediate health effects can be caused by exposure to malathion?
Malathion can cause nausea, vomiting,
stomach cramps, and diarrhea, as well as confusion, blurred
vision, sweating, muscle twitching, irregular heartbeat, convulsions,
and death. Symptoms occur when malathion is inhaled, swallowed,
or absorbed through the skin. Breathing the solvent used to
dissolve the pesticide may cause dizziness, headache, and
nausea. Generally, the more serious the exposure, the more
severe the symptoms.
Can malathion poisoning be treated?
For minor exposures (for example, breathing
the pesticide solvent), the only treatment needed is fresh
air. For serious malathion poisoning, thorough washing of
all exposed skin, removal and burning of exposed clothing,
and hospitalization and administration of an antidote may
be needed.
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, a patient may
feel ill for several weeks.
What tests can be done if a person has been exposed to malathion?
Specific tests for the presence of malathion
or its breakdown product in blood and urine generally are
not useful to the doctor. If a severe exposure has occurred,
blood and urine analyses and other tests may show whether
damage has been done to the brain, heart, lungs, and nerves.
Testing is not needed in every case.
Where can more information about malathion be found?
More information about malathion 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.
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[ ] Call your doctor or the Emergency
Department if you develop any unusual signs or symptoms within
the next 24 hours, especially:
- irritability, confusion, or fatigue
- coughing, wheezing, or shortness of breath
- nausea, vomiting, cramps, or diarrhea
- muscle weakness or twitching
- blurred vision
[ ] 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.