| | Malathion Basic information |
| | Malathion Chemical Properties |
| Melting point | 2.85°C | | Boiling point | 156°C | | density | 1.2076 | | vapor pressure | 7.95 at 25 °C (gas saturation method-GC, Kim et al., 1984) | | refractive index | nD25 1.4985 | | Fp | -18 °C | | storage temp. | APPROX 4°C
| | solubility | Slightly soluble in water, miscible with acetone, with cyclohexane, with ethanol (96 per cent) and with vegetable oils. | | form | liquid | | Specific Gravity | 1.23 (25℃) | | Water Solubility | 0.0145 g/100 mL | | Henry's Law Constant | (x 10-9 atm?m3/mol):
4.89 at 25 °C (wetted-wall column, Fendinger and Glotfelty, 1990) | | Exposure limits | NIOSH REL: TWA 10 mg/m3, IDLH 250 mg/m3; OSHA PEL: TWA
15 mg/m3; ACGIH TLV: TWA 10 mg/m3. | | Stability: | Stable. Incompatible with oxidizing agents, metals. | | LogP | 2.360 | | CAS DataBase Reference | 121-75-5(CAS DataBase Reference) | | IARC | 2A (Vol. 30, Sup 7, 112) 2017 | | NIST Chemistry Reference | Malathion(121-75-5) | | EPA Substance Registry System | Malathion (121-75-5) |
| | Malathion Usage And Synthesis |
| Description | Malathion, a clear amber liquid, is sparingly soluble in water but soluble in a majority of
organic solvents. The U.S. Environmental Protection Agency (U.S. EPA) grouped malathion
under GUP, meaning general use pesticide. It is used as an insecticide as well as
an acaricide for the control of pests. Malathion is used for the control of sucking insects
and chewing insects on fruits and vegetables. Malathion is an effective insecticide for the
control of several household pests such as houseflies, cockroaches, mosquitoes, aphids,
animal ectoparasites, and human head and body lice. Malathion is also found in formulations
with many other pesticides. | | Chemical Properties | Malathion is a clear amber liquid. It is sparingly soluble in water, but soluble in a majority of organic solvents. The US EPA grouped malathion under GUP. It is used as an insecticide as well as an acaricide for the control of pests. Malathion is used for the control of sucking insects and chewing insects on fruits and vegetables, and is an effective insecticide for the control of several household pests, such as housefl ies, cockroaches, mosquitos, aphids, animal ectoparasites, and human head and body lice. It is also found in formulations with many other pesticides | | Chemical Properties | Malathion is a deep-brown to yellow liquid
with a garlic-like odor. Clear and colorless when pure;
freezing/melting point5 3C; | | Physical properties | Clear, yellow to yellow-orange to brown liquid with an unpleasant garlic, skunk, or mercaptanslike
odor | | Originator | Prioderm,Purdue Frederick,US,1982 | | Uses | Malathion is used to control a wide spectrum of insect pests in
many types of crops and disease vectors in public health programmes.
It is also used to control ectoparasites of both humans and animals. | | Uses | Insecticide for control of sucking and chewing insects and spider mites on vegetables,
fruits, ornamentals, field crops, greenhouses, gardens and forestry. | | Uses | Used as an insecticide | | Uses | Organophosphorus insecticide. | | Uses | anticholinergic | | Uses | Malation is a pestanal and used primarily as an insecticide. | | Definition | ChEBI: A diester that is butanedioate substituted by a (dimethoxyphosphorothioyl)sulfanediyl group at position 2. | | Indications | Malathion (Ovide) is highly effective in the prevention and treatment of pediculosis.
It displays 95% ovicidal activity and has no scabicidal activity. It works through
cholinesterase inhibition. | | Manufacturing Process | The feed materials for malathion manufacture are O,O-dimethyl phosphorodithioic acid and diethyl maleate or fumarate which react according to the equation:
An antipolymerization agent such as hydroquinone may be added to the
reaction mixture to inhibit the polymerization of the maleate or fumarate
compound under the reaction conditions. This reaction is preferably carried
out at a temperature within the range of 20°C to 150°C. This reaction is
preferably carried out at atmospheric pressure. Reaction time of 16 to 24
hours have been specified for this reaction by J.T. Cassaday. The reaction is
preferably carried out in a solvent such as the low molecular weight aliphatic
monohydric alcohols, ketones, aliphatic esters, aromatic hydrocarbons or
trialkyl phosphates.
The reaction may be accelerated by using an aliphatic tertiary amine catalyst,
usually within the range of 0.2 to 2.0% based on the total weight of the
reactants. A stirred, jacketed reactor of conventional design may be used.
After cooling, the reaction mixture may be taken up in benzene. It is then
washed with 10% Na2CO3 and with water. The organic layer is dried over
anhydrous Na2SO4, filtered and concentrated in vacuo to give the final product
as residue. | | Therapeutic Function | Pediculicide | | General Description | Malathion, 2-[(dimethoxyphosphinothioyl)thio]butanedioic acid diethyl ester, is a water-insolublephosphodithioate ester that has been used as an agriculturalinsecticide. Malathion is a poor inhibitor of cholinesterases.Its effectiveness as a safe insecticide is a result of the differentrates at which humans and insects metabolize the chemical.Microsomal oxidation, which causes desulfuration,occurs slowly to form the phosphothioate (malaoxon),which is 10,000 times more active than the phosphodithioate(malathion) as a cholinesterase inhibitor. Insects detoxifythe phosphothioate by a phosphatase, forming dimethylphosphorothioate, which is inactive as an inhibitor.Humans, however, can rapidly hydrolyze malathion by acarboxyesterase enzyme, yielding malathion acid, a stillpoorer inhibitor of AChE. Phosphatases and carboxyesterasesfurther metabolize malathion acid to dimethylphosphothioate. | | General Description | Yellow to dark-brown liquid with a skunk-like odor. Sinks in water. Freezing point is 37°F. | | Air & Water Reactions | Insoluble in water. | | Reactivity Profile | Malathion is a yellow to brown liquid that solidifies at 2.9° C, moderately toxic. Organic phosphate insecticide, acts as an inhibitor of cholinesterase. When heated to decomposition Malathion emits toxic fumes of oxides of sulfur and phosphorus [Lewis, 3rd ed., 1993, p. 789]. | | Hazard | Absorbed by skin, cholinesterase inhibitor.
Questionable carcinogen. | | Health Hazard | Acute and prolonged period of exposures to high concentrations of malathion cause poisoning in animals and humans. The symptoms of poisoning include, but are not limited to, numbness, tingling sensations, incoordination, headache, dizziness, tremor, nausea, abdominal cramps, sweating, blurred vision, diffi culty breathing or respiratory depression, and slow heart beat. Very high doses may result in unconsciousness, incontinence, and convulsions, or fatality. Malathion did not indicate any kind of delayed neurotoxicity in experimental studies with hens. Reports have indicated that because of and accidental exposures through severe skin absorption, malathion caused poisoning and fatalities among workers associated with the malaria control operations in Pakistan. In certain cases, development of pulmonary fi brosis following the poisoning has also been observed. Reports have indicated that malathion is neither mutagenic nor teratogenic to animals and humans. In animals, malathion induced liver carcinogenicity at doses that were considered excessive. However, available information is not adequate to confi rm the carcinogenicity of malathion to animals and humans. The IARC has determined that malathion is unclassifi able as to its carcinogenicity to humans. The IARC observed that the available data do not provide evidence that malathion or its metabolite malaoxon is carcinogenic to experimental animals and there is no data on humans and classifi ed as Group 3 meaning, not classifi able as to carcinogenicity for humans. | | Health Hazard | Exposure to fumes from a fire or to liquid causes headache, blurred vision, constricted pupils of the eyes, weakness, nausea, cramps, diarrhea, and tightness in the chest. Muscles twitch and convulsions may follow. The symptoms may develop over a period of 8 hours. | | Health Hazard | Cholinesterase inhibitor; toxic propertiessimilar to those of parathion; however,less toxic than parathion; moderately toxicby ingestion and possibly other routes ofexposure; toxic symptoms include excessivesalivation, lacrimation, blurred vision, con-striction of the pupils, nausea, vomiting,abdominal pain, and difficulty in breathing;also coma and death can result form largeintake; ingestion of 10–25 g could be fatalto adult humans; skin contact can produceallergic sensitization reaction; also absorbedthrough skin, causing systemic poisoning;experimental teratogen; LD50 data reportedin the literature show wide variation.
LD50 oral (rate): 300–2800 mg/kg
LD50 skin (mouse): 2000–3000 mg/kg
Benslama et al. (2004) have reported twounusual cases of malathion poisoning with arare-type of complication from “intermediatesyndrome” arising 2 to 4 days after the onsetof cholinergic effects. The symptoms wererespiratory paresis with difficulties of wean-ing from assisted respiratory, deficit of proximal limbs, neck flexors and cranial nerves.The authors attributed this syndrome to pro-longed inhibition of acetyl-cholinesterasesand not to any muscular fiber’s necrosis. | | Agricultural Uses | nsecticide: Not approved for use in EU countries. Malathion
is a non-systemic, wide-spectrum organophosphate insecticide.
It was one of the earliest organophosphate insecticides
developed (introduced in 1950). Malathion is suited
for the control of sucking and chewing insects on fruits,
vegetables, citrus, cotton, corn, sorghum, ornamentals and
stored products, and is also used to control mosquitoes,
flies, household insects, farm and livestock parasites (ectoparasites),
and head and body lice. Malathion may also be
found in formulations with many other pesticides; the U.S.
EPA lists 2,283 current and canceled labels of products
containing malathion. Malathion is marketed as 99.6%
technical grade liquid. Available formulations include wettable
powders (25% and 50%), emulsifiable concentrates,
dusts and aerosols. | | Trade name | AI3-17034®; AGRICHEM
GREENFLY SPRAY®; ALCO® Malathion; ALL
PURPOSE GARDEN INSECTICIDE®; AMERICAN
CYANAMID 4,049®; ATRAPA 5E®; BAN-MITE®;
CALMATHION®; CARBETOVUR®; CARBETOX®;
CELTHION®; CHEMATHION®; CIMEXAN®;
COMPOUND 4049®; CROMOCIDE®; CYTHION®;
SPRAY CONCENTRATE®; CYTHION®; DETMOL
MA®; DETMOL® 96%; DETMOL MALATHION®;
DURAMITEX®; EMMATOS EXTRA®; EL
4049®; EMMATON®; EMMATOS®; ETIOL®;
EVESHIELD CAPTAN/MALATHION®; EXATHIOS®;
EXTERMATHION®; FYAFANON®; FISONS
GREENFLY AND BLACKFLY KILLER®; FOG®
3; FORMAL®; FORTHION®; FOSFOTHION®;
FOSFOTION®; FYFANON®; ETHIOLACAR®;
GREEN DEVIL®; GREENFLY AEROSOL
SPRAY®; HILTHION®; KARBOFOS®; KOPTHION
®; KYPFOS®; MALACIDE®; MALAFOR®;
MALAGRAN®; MALAKILL®; MALAMAR®;
MALASOL®; MALASPRAY®; MALATAF®;
MALATHION 60®; MALATHION E50®; MALATOL®;
MALTOX®; MOSCARDA®; ORTHO MALATHION®;
PBI CROP SAVER®; PRENTOX®; PRIODERM®;
PROKIL® Malathion; SADOFOS®; SADOPHOS®;
SF® 60; SIPTOX I®; SUMITOX®; TAK®; TM-4049®;
VETIOL®; ZITHIOL® | | Contact allergens | This organophosphorus pesticide is used as an insecticide and an acaricide, particularly against head lice. Sensitization was reported in farmers. | | Safety Profile | A human poison by
ingestion and skin contact. Can penetrate
intact skin. An experimental poison by
ingesuon, inhalation, intraperitoneal,
intravenous, intraarterial, and subcutaneous
routes. Human systemic effects by ingestion:
coma, blood pressure depression, and
dfficulty in breathmg. Questionable carcinogen. An experimental teratogen.
Other experimental reproductive effects.
Human mutation data reported. Has caused
allerglc sensitization of the skin. An organic
phosphate cholinesterase inhibitor. When
heated to decomposition it emits toxic
fumes of POx and SOx. See also
PHOSPHATES and PARATHION. | | Potential Exposure | Malathion is marketed as 99.6%
technical grade liquid. Available formulations include
wetable powders (25% and 50%), emulsifiable concentrates, dusts, and aerosols. Malathion is used as a broad
spectrum insecticide and acaricide in the control of certain
insect pests on fruits, vegetables, and ornamental plants.
It has been used in the control of houseflies, mosquitoes,
lice; and on farm and livestock animals.
| | Carcinogenicity | There was no evidence of carcinogenicity
in rats given diets that contained 4700 or
8150 ppm (about 270 mg/kg and 466 mg/kg) for 80 weeks
and observed for an additional 33 weeks, in rats given diets
that contained 2000 or 4000 ppm malathion (about 115 mg/
kg/day and 230 mg/kg/day) for 103 weeks, or in rats given
diets that contained 500 or 1000 ppm malaoxon for 103
weeks . | | Environmental Fate | Biological. Walker (1976) reported that 97% of malathion added to both sterile and
nonsterile estuarine water was degraded after incubation in the dark for 18 days. Complete
degradation was obtained after 25 days. Malathion degraded fastest in nonsterile soils and
decomposed faster in soils that were sterilized by gamma radiation than in soils that were
sterilized by autoclaving. After 1 day of incubation, the amounts of malathion degradation
that occurred in autoclaved, irradiated and nonsterile soils were 7, 90 and 97%, respectively
(Getzin and Rosefield, 1968). Degradation of malathion in organic-rich soils was 3 to 6
times higher than in soils not containing organic matter. The half-life in an organic-rich
soil was about 1 day (Gibson and Burns, 1977). Malathion was degraded by soil microcosms
isolated from an agricultural area on Kauai, HI. Degradation half-lives in the laboratory and field experiments were 8.2 and 2 hours, respectively. Dimethyl phosphorodithioic
acid and diethyl fumarate were identified as degradation products (Miles and
Takashima, 1991). Mostafa et al. (1972) found the soil fungi Penicillium notatum, Aspergillus
niger, Rhizoctonia solani, Rhizobium trifolii and Rhizobium leguminosarum converted
malathion to the following metabolites: malathion diacid, dimethyl phosphorothioate,
dimethyl phosphorodithioate, dimethyl phosphate, monomethyl phosphate and thiophosphates.
Malathion also degraded in groundwater and seawater but at a slower rate (halflife
4.7 days). Microorganisms isolated from paper-mill effluents were responsible for the
formation of malathion monocarboxylic acid (Singh and Seth, 1989).
Paris et al. (1975) isolated a heterogenous bacterial population that was capable of
degrading low concentrations of malathion to b-malathion monoacid. About 1% of the
original malathion concentration degraded to malathion dicarboxylic acid, O,O-dimethyl
Matsumura and Bousch (1966) isolated carboxylesterase(s) enzymes from the soil
fungus Trichoderma viride and a bacterium Pseudomonas sp. obtained from Ohio soil
samples that were capable of degrading malathion. Compounds identified included diethyl
maleat
Soil. In soil, malathion was degraded by Arthrobacter sp. to malathion monoacid,
malathion dicarboxylic acid, potassium dimethyl phosphorothioate and potassium dimethyl
phosphorodithioate. After 10 days, degradation yields in sterile and nonsterile soils
were 8, 5, 19% and 92, 94, 81%, respectively (Walker and Stojanovic, 1974). Chen et al.
(1969) reported that the microbial conversion of malathion to malathion monoacid was a
result of demethylation of the O-methyl group. Malathion was converted by unidentified
microorganisms in soil to thiomalic acid, dimethyl thiophosphoric acid and diethylthiomaleate
(Konrad et al., 1969).
The half-lives for malathion in soil incubated in the laboratory under aerobic conditions
ranged from 0.2 to 2.1 days with an average of 0.8 days (Konrad et al., 1969; Walker and
Stojanovic, 1973; Gibson and Burns, 1977). | | Metabolic pathway | Malathon is a very widely used insecticide of low mammalian toxicity.
Many studies have identified the products of degradation in a very wide
range of organisms and the following is necessarily a selection of only
some of them which have been used to illustrate the principles of its
metabolism.
The much more toxic isomalathion, which can be produced by heating
malathion, is sometimes present in commercial samples and is a very
active acetylcholinesterase dubitor. The principal route of malathion
metabolism in animals and plants is via de-esterification to the α- and β-malathion
monocarboxylic acids followed by further metabolism to the
dicarboxylic acid. This is a facile esterase-catalysed detoxification route
which is considered to be responsible for the low vertebrate toxicity of
malathion. The analytical methods which have been used to determine
the structure of the metabolites have frequently not distinguished
between which monocarboxylic acid isomer is formed, and what evidence
there is is often equivocal as to which is actually produced. Malathion can
decompose in aqueous solution via an elimination mechanism yielding
diethyl fumarate and O,O-dimethyl phosphorodithioate; however,
derivatives of fumaric acid are usually only encountered in small
amounts in vivo indicating that this is probably not an important route of
detoxification. There is evidence that the dicarboxylic acid derivative is
not subject to this elimination reaction. Most studies indicate that the
selective toxicity of malathion can be accounted for by the balance
between bioactivation (oxidative desulfuration) yielding the active
acetylcholinesterase inhibitor malaoxon and detoxification via deesterification.
Insecticide resistance is frequently found to involve the malathion-resistant insects being able to de-esterify malathion rapidly. | | Shipping | UN2783 Organophosphorus pesticides, solid,
toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials | | Degradation | When heated, malathion waS isomerised via a thiono-thiolo rearrangement
to yield isomalathion (2). This reaction proceeded rapidly above
100 °C (O'Brien, 1956). [14C-succinyl]Malathion was hydrolysed rapidly in
neutral and basic solution. The half-lives at pH values 5, 7 and 9 were
107, 6.2 and 0.5 days, respectively, at 25 °C. The identified products of
hydrolysis were, in order of decreasing abundance, α- and β-malathion
monoacids (3 and 4), monoethyl fumarate (5), diethyl thiomalate (6) and
malathion dicarboxylic acid (7). Products were identified by TLC, GLC
and MS (PSD, 1995). It was probable that the mechanism for the production
of monoethyl fumarate (5) involved a base-catalysed elimination (El)
reaction of malathion monoacid with O,O-dimethyl phosphorodithloate
(8) acting as the leaving group. In a second study which monitored the
products of hydrolysis at pH 8 and 25 °C by GLC, diethyl fumarate (9) and O,O-dimethyl phosphorodithioate (8) were identified in addition to
the compounds found in the previous work. Higher temperatures
favoured the formation of elimination (fumarate) products. Malathion
dicarboxylic acid did not give any elimination products but instead
produced O,O-dimethyl phosphorothioate (10) and thiomalic acid (12).
The end products of base-catalysed degradation of malathion were
fumaric acid (11), O,O-dimethyl phosphorodithioate (8), O,O-dimethyl
phosphorothioate (10) and thiomalic acid (12) (PSD, 1995).
The aqueous photolysis of malathion irradiated with a xenon arc lamp
was studied in sterile water buffered at pH 4 in order to minimise hydrolytic
and microbial breakdown. The half-life of the irradiated sample was
98 days, approximately one-third of the value for a sample kept in the
dark. The major metabolites which were identified in both the irradiated
and dark samples were the same although larger amounts were found in
the irradiated samples. These were desmethylmalathion (13), and the α-and β-malathion monoacids (3 and 4). Minor metabolites were diethyl maleate (14), monoethyl maleate (15) and diethyl thiomalate (6). Analysis was by TLC and HPLC (PSD, 1995). | | Toxicity evaluation | Acute oral LD50 for rats: 1,375-2,800 mg/kg | | Incompatibilities | Reacts violently with strong oxidizers,
magnesium, alkaline pesticides. Attacks metals including
iron, steel, tin plate; lead, copper; and some plastics, coatings, and rubbers | | Waste Disposal | Malathion is reported to be
“hydrolyzed almost instantly” at pH 12; 50%; hydrolysis at
pH 0 requires 12 hours. Alkaline hydrolysis under controlled conditions (0.5 n NaOH in ethanol) gives quantitative yields of (CH3O)2P(S)SNa, whereas hydrolysis in
acidic media yields (CH3O)2P(S)OH. On prolonged contact
with iron or iron-containing material, it is reported to break
down and completely lose insecticidal activity. Incineration
together with a flammable solvent in a furnace equipped
with afterburner and scrubber is recommended. In accordance with 40CFR165, follow recommendations for the
disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by
contacting your local or federal environmental control
agency, or by contacting your regional EPA office |
| | Malathion Preparation Products And Raw materials |
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