121-75-5

Deep Brown to Yellow Liquid

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

anticholinergic

Malation is a pestanal and used primarily as an insecticide.

Used as an insecticide

ChEBI: A diester that is butanedioate substituted by a (dimethoxyphosphorothioyl)sulfanediyl group at position 2.

Insecticide.

Yellow to dark-brown liquid with a skunk-like odor. Sinks in water. Freezing point is 37°F.

MALATHION(121-75-5) 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(121-75-5) emits toxic fumes of oxides of sulfur and phosphorus [Lewis, 3rd ed., 1993, p. 789].

Insoluble in water.

Absorbed by skin, cholinesterase inhibitor. Questionable carcinogen.

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.

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.

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.

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Speed in removing material from skin is of extreme importance. Shampoo hair promptly if contaminated. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

UN2783 Organophosphorus pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials

Reacts violently with strong oxidizers, magnesium, alkaline pesticides. Attacks metals including iron, steel, tin plate; lead, copper; and some plastics, coatings, and rubbers

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

Clear, yellow to yellow-orange to brown liquid with an unpleasant garlic, skunk, or mercaptanslike odor

Prioderm,Purdue Frederick,US,1982

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.

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.

Pediculicide

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.

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®

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 .

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).

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.

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with thischemical you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated, uninhabited area below 25℃. Store to avoidcontact with oxidizers and alkaline pesticides. Store wherepossible leakage from containers cannot endanger theworker. Maintain regular inspection of containers for anyleakage. Sources of ignition, such as smoking and openflames, are prohibited where this chemical is handled, used,or stored.

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).

Acute oral LD₅₀ for rats: 1,375-2,800 mg/kg