Methyl Parathion (HCID 178785329)

Overview

Methyl parathion is an insecticide that does not occur naturally in the environment. Pure methyl parathion exists as white crystals. Impure methyl parathion is a brownish liquid that smells like rotten eggs.Methyl parathion is used to kill insects on farm crops, especially cotton. The EPA now restricts how methyl parathion can be used and applied; only trained people are allowed to spray it. Methyl parathion can no longer be used on food crops commonly consumed by children.

Names & identifiers

Preferred name: Methyl Parathion
IUPAC: dimethoxy-(4-nitrophenoxy)-sulfanylidene-λ5-phosphane
English name: Bladan-m
Molecular formula: C8H10NO5PS
Molecular weight: 263.207461

Names & synonyms

Parathion-methylMETHYL PARATHION298-00-0MethylparathionDimethyl parathionParathion methylMetacideMetaphosMetronDalfMetafosVofatox

Show more names

Ai3-17292

WofatoxFolidol MCekumethionMethylthiophosOleovofotoxThiophenitAzophosDevithion

Database identifiers

CAS: 63653-66-7
ChEMBL: CHEMBL346516
ChEBI: CHEBI:38746
UNII: 41BCL2O91D
EC Number: 206-050-1
Nikkaji: J2.981E

Properties

Computed structural properties

XLogP: 2.9
Topological polar surface area: 106 Å²
Hydrogen bond donors: 0
Hydrogen bond acceptors: 6
Rotatable bonds: 4
Heavy atoms: 16
Formal charge: 0
Complexity: 279

Experimental & physicochemical properties

Chemical ClassesFlammable agents - 3rd degree

SpringerMaterials PropertiesCrystal structure

Pesticides · 6 items

Pesticide -> EPA IRIS

Insecticides, Repellants

Active substance -> EU Pesticides database: Not approved

Pesticides -> Organophosphate Insecticides

Insecticides

Pesticide (Parathion methyl) -> USDA PDB

LogP · 3 items

log Kow = 2.86

2-3

2.86

Odor · 2 items

Pungent, garlic-like odor

Odorless

Density · 6 items

1.358 at 68 °F (EPA, 1998) - Denser than water; will sink

1.358 g/cu cm at 20 °C

1.4 g/cm³

1.36

1.358 @ 20°C

1.36

Safety & regulation

GHS classification

GHS Classification · 6 items

Danger

H226: Flammable liquid and vapor [Warning Flammable liquids]

P210, P233, P240, P241, P242, P243, P260, P262, P264, P270, P271, P273, P280, P284, P301+P316, P302+P352, P303+P361+P353, P304+P340, P316, P319, P320, P321, P330, P361+P364, P370+P378, P391, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement)

Danger

H226 (93.3%): Flammable liquid and vapor [Warning Flammable liquids]

P210, P233, P240, P241, P242, P243, P260, P262, P264, P270, P271, P273, P280, P284, P301+P316, P302+P352, P303+P361+P353, P304+P340, P316, P319, P320, P321, P330, P361+P364, P370+P378, P391, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement)

Hazard information

Regulatory Information · 4 items

Hazard Traits - Developmental Toxicity; Environmental tox; Neurotoxicity

Regulation (EC) No 1107/2009 (amended)

03/166/EC

The New Jersey Worker and Community Right to Know Act requires public and private employers to provide information about hazardous substances at their workplaces. (N.J.S.A. 34:5A-1 et. seq.)

Other Safety InformationIMAP assessments - Phosphorothioic acid, O,O-dimethyl O-(4-nitrophenyl) ester: Environment tier I assessment

DOT LabelPoison Flammable Liquid

Fire Hazards · 2 items

Poisonous gases are produced in fire and when heated. Decomposition may lead to sufficient internal pressure to cause the container to rupture violently. Avoid oxidizing materials. Unstable. High temperatures (120F) cause decomposition. (EPA, 1998)

Combustible. Liquid formulations containing organic solvents may be flammable. Gives off irritating or toxic fumes (or gases) in a fire.

Health HazardsThis material is extremely toxic; the probable oral lethal dose is 5-50 mg/kg, or between 7 drops and 1 teaspoonful for a 150-lb. person. Chronic toxicity does not appear to be a major consideration. (EPA, 1998)

Hazards Summary · 2 items

Methyl parathion is an insecticide that does not occur naturally in the environment. Pure methyl parathion exists as white crystals. Impure methyl parathion is a brownish liquid that smells like rotten eggs.Methyl parathion is used to kill insects on farm crops, especially cotton. The EPA now restricts how methyl parathion can be used and applied; only trained people are allowed to spray it. Methyl parathion can no longer be used on food crops commonly consumed by children.

Classified as highly toxic, and most formulations may be used only by certified applicators; [EXTOXNET] Allergic contact dermatitis reported in sprayers; [Kanerva, p. 1431] The average of two baseline respective cholinesterase activity determinations three days apart, with no exposures to enzyme inhibiting pesticides for at least 30 days, is recommended for each worker prior to exposure to cholinesterase inhibitors because of large inter-individual differences in published baseline values. To be established at least once a year. Removal from workplace exposures is recommended until the cholinesterase activity returns to within 20% of baseline. [TLVs and BEIs]

Safety & protection

Fire Fighting · 2 items

Fight fire from maximum distance. Dike fire control water for later disposal; do not scatter the material. Wear special protective clothing.

Use water spray, foam, powder, carbon dioxide.

First Aid Measures · 4 items

Fresh air, rest. Artificial respiration may be needed. Refer for medical attention.

Remove contaminated clothes. Rinse and then wash skin with water and soap. Refer for medical attention .

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Induce vomiting (ONLY IN CONSCIOUS PERSONS!). Give a slurry of activated charcoal in water to drink. Refer immediately for medical attention.

First Aid · 2 items

Note: Parathion-methyl is a cholinesterase inhibitor.

(General first aid procedures)

Safe StorageStore in an area without drain or sewer access. Keep in a well-ventilated room. Separated from food and feedstuffs.

Exposure Control and Personal Protection · 1 item

Biological Exposure Indices (BEI) [ACGIH] - Acetylcholinesterase activity in red blood cells = 70% of individual's baseline; Butylcholinesterase activity in serum or plasma = 60% of individual's baseline; Sample at end of shift; [TLVs and BEIs]

Fire Fighting Procedures · 2 items

Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide. Advice for firefighters: Wear self contained breathing apparatus for fire fighting if necessary.

Fire Extinguishing Media: Dry chemical, carbon dioxide for small fires. Water spray or foam for large fires.

Toxicology

Toxicological InformationCDC-ATSDR Toxicological Profile

Body Burden · 1 item

A metabolite of ethyl and methyl parathion (p-nitrophenol) was detected in 2.4% of 6990 urine samples collected from USA persons (12-74 yrs old) between 1976-80(1). 15,904 urine samples from residents of innercity USA homes in seven states which had been illegally treated with methyl parathion for control of cockroaches contained p-nitrophenol at a mean concentration of 75 ug/L, range of <25 to 45,000 ug/L, and a 57% frequency of detection(2).

Treatment · 1 item

If the compound has been ingested, rapid gastric lavage should be performed using 5% sodium bicarbonate. For skin contact, the skin should be washed with soap and water. If the compound has entered the eyes, they should be washed with large quantities of isotonic saline or water. In serious cases, atropine and/or pralidoxime should be administered. Anti-cholinergic drugs work to counteract the effects of excess acetylcholine and reactivate AChE. Atropine can be used as an antidote in conjunction with pralidoxime or other pyridinium oximes (such as trimedoxime or obidoxime), though the use of '-oximes' has been found to be of no benefit, or possibly harmful, in at least two meta-analyses. Atropine is a muscarinic antagonist, and thus blocks the action of acetylcholine peripherally.

Interactions · 5 items

Pre-treatment of mice with piperonyl butoxide, the mono-oxygenase inhibitor, before challenge with parathion and methyl parathion led to two-fold potentiation and forty-fold antagonism, respectively. ... Diminution in toxicity of methyl parathion ... must be largely to inhibition of oxon formation. ... When mice were pretreated with diethyl maleate, which depletes hepatic glutathione, methyl parathion toxicity was potentiated four-fold.

In mice and rats, pretreatment with cimetidine (75 mg/kg/ip) 30 min prior to methyl parathion administration reduced lethality and delayed the onset of cholinergic signs of toxicity. When cimetidine was administered simultaneously with methyl parathion to mice, neither methyl parathion induced lethality nor cholinergic signs of toxicity were altered. Cimetidine pretreatment failed to decrease parathion induced toxicity in mice.

A toxic unit approach was used to test the response addition model for mixtures of pesticides with differing modes of action. Atrazine was tested in binary and ternary combinations with the organochlorine insecticide methoxychlor and organophosphate insecticide methyl-parathion. Atrazine was also tested in binary combinations with additional organophosphates. The toxic unit for atrazine was set slightly below its water solubility limits (toxic unit = 20 ppm), which is well below its 96-hr 50% effective concentration for the fourth instar of the midge, Chironomus tentans. In 96-hr acute toxicity tests using C. tentans, atrazine was found to produce synergistic (greater than additive) toxicity in a binary mixture with methyl-parathion. Less than additive toxicity was found for the combination of atrazine with methoxychlor (likely due to the low toxic unit assigned to atrazine). The ternary combination of atrazine + methyl-parathion + methoxychlor was found to be marginally synergistic. Results of toxicity tests with atrazine in binary combinations with other organophosphates indicate more than additive toxicity for all compounds except mevinophos. Possible hypotheses are presented in an attempt to explain the noted synergistic relationship between atrazine and various organophosphorous insecticides. These results suggest that the response addition model does not always accurately predict mixture toxicity for chemicals with differing modes of action.

This study, carried out on the estuarine crab Chasmagnathus granulata, had two main objectives: (i) to correlate inhibition of the cholinesterase activity in the thoracic ganglia caused by a commercial formulation of methyl parathion (O,O-dimethyl-o-p-nitro-phenyl phosphorothionate) with crab mortality; and (ii) to investigate the methyl parathion bioactivation mechanisms. In crabs not pre-exposed to sesamol (3, 4-methylenedioxyphenol), in vivo cholinesterase inhibition showed a dose-related response (ID50 = 0.36 mg/kg, it showed not to be a good tool to establish an effective dose since small amounts of inhibition were correlated to mortalities as high as 50%. Methyl parathion was more toxic to crabs not pre-exposed to sesamol (96 hr LD50 = 0.21 mg/kg pre-exposed to the MFO-inhibitor (96 hr LD50 = 1.02 mg/kg). Pre-exposure to sesamol seems to prevent methyl parathion oxidation, and consequently, its toxicity since the cholinesterase inhibition in crabs pre-exposed to sesamol was lower than that observed in those not pre-exposed to sesamol. In accordance to the idea that the anticholinesterase property of methyl parathion is acquired only after its oxidation, a higher in vitro cholinesterase inhibition induced by chemically oxidized methyl parathion (IC50 = 0.114 uM) in relation to that caused by the fresh methyl parathion (IC50 = 19.2 uM) was observed.

For more Interactions (Complete) data for METHYL PARATHION (41 total), please visit the HSDB record page.

Target Organs · 3 items

Developmental (effects while organs are developing), Hematological (Blood Forming), Neurological (Nervous System)

Hematologic

Eyes, skin, respiratory system, central nervous system, cardiovascular system, blood cholinesterase

Health Effects · 1 item

Acute exposure to cholinesterase inhibitors can cause a cholinergic crisis characterized by severe nausea/vomiting, salivation, sweating, bradycardia, hypotension, collapse, and convulsions. Increasing muscle weakness is a possibility and may result in death if respiratory muscles are involved. Accumulation of ACh at motor nerves causes overstimulation of nicotinic expression at the neuromuscular junction. When this occurs symptoms such as muscle weakness, fatigue, muscle cramps, fasciculation, and paralysis can be seen. When there is an accumulation of ACh at autonomic ganglia this causes overstimulation of nicotinic expression in the sympathetic system. Symptoms associated with this are hypertension, and hypoglycemia. Overstimulation of nicotinic acetylcholine receptors in the central nervous system, due to accumulation of ACh, results in anxiety, headache, convulsions, ataxia, depression of respiration and circulation, tremor, general weakness, and potentially coma. When there is expression of muscarinic overstimulation due to excess acetylcholine at muscarinic acetylcholine receptors symptoms of visual disturbances, tightness in chest, wheezing due to bronchoconstriction, increased bronchial secretions, increased salivation, lacrimation, sweating, peristalsis, and urination can occur. Certain reproductive effects in fertility, growth, and development for males and females have been linked specifically to organophosphate pesticide exposure. Most of the research on reproductive effects has been conducted on farmers working with pesticides and insecticdes in rural areas. In females menstrual cycle disturbances, longer pregnancies, spontaneous abortions, stillbirths, and some developmental effects in offspring have been linked to organophosphate pesticide exposure. Prenatal exposure has been linked to impaired fetal growth and development. Neurotoxic effects have also been linked to poisoning with OP pesticides causing four neurotoxic effects in humans: cholinergic syndrome, intermediate syndrome, organophosphate-induced delayed polyneuropathy (OPIDP), and chronic organophosphate-induced neuropsychiatric disorder (COPIND). These syndromes result after acute and chronic exposure to OP pesticides.

Environmental Fate · 5 items

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values ranging from 366 to 1,516(2,3) indicate that methyl parathion is expected to have moderate to low mobility in soil(SRC). Volatilization of methyl parathion from moist soil surfaces is not expected to be an important fate process(SRC) given a Henry's Law constant of 1.0X10-7 atm-cu m/mole(4). Methyl parathion is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 3.5X10-6 mm Hg at 25 °C(5). Hydrolysis is expected to be an important process in moist soils(SRC), since methyl parathion hydrolyzes in natural water with half-lives ranging from 6.5 to 13 days at 40 °C and pH values less than 8(6). Utilizing loam soils maintained at 10 and 33 kPa soil-water tension, 14C-methyl parathion was approximately 50% mineralized in 28 days(7), indicating that biodegradation is an important environmental fate process in soil(SRC).

TERRESTRIAL FATE: Simulated spillage of emulsifiable concentrate and microencapsulated formulations of methyl parathion on soil were studied. Persistence of residues from both formulations spilled as concentration and as simulated drum rinses were followed for up to 45 mo. Spillage of encapsulated formulation resulted in the formation of a solid cake-like deposit on the soil surface. At 45 mo, soil residues had decreased by 64% for emulsifiable concentrate spills, and 68% for the soil beneath the cake. Residue in the cake itself only decr by 31%. Soil residue levels from simulated drum rinses were essentially innocuous by 45 mo for the emulsifiable concentrate and by 1 yr for the microencapsulated material.

TERRESTRIAL FATE: 73 acres of alfalfa in Vernal, Utah, were sprayed with an emulsifiable concentrate (EC) containing 6 lb/gal ethyl parathion and 3 lb/gal methyl parathion. The material was applied at 4.15X10-2 gal/acre. Wind conditions were negligible. Samples were taken from the sprayed plot (sites A and B) and from an adjoining non-target pasture (site C). Immediately after treatment, methyl parathion residues averaged 40% of ethyl parathion levels at the 3 sampling stations. Foliar residues of the parent cmpd dissipated rapidly with time. At Site A, the residues dropped below 1.25 mg/kg within 28 hr for methyl parathion. First-order half-life of methyl parathion was 12 hr.

AQUATIC FATE: Based on a classification scheme(1), Koc values ranging from 366 to 1,516(2,3) indicate that methyl parathion is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(4) based upon a Henry's Law constant of 1.0X10-7 atm-cu m/mole(5). According to a classification scheme(6), a BCF range of 8.3 to 959(7,8) suggests bioconcentration in aquatic organisms is low to moderate(SRC). However, methyl parathion is rapidly metabolized in some aquatic organisms(9). Aqueous photolysis half-lives range from 8 to 38 days(10). Hydrolysis is expected to be an important environmental fate process since this compound exhibits half-lives from 6.5 to 13 days at 40 °C in natural waters; pH values were less than 8(11). The half-life of methyl parathion in untreated estuarine sediment water studies was 1.2 days (95% confidence limit 0.60-2.0 days). The half-life of methyl parathion in untreated estuarine sediment water studies was 1.2 days (95% confidence limit 0.60-2.0 days)(12). Utilizing a river die-away test using water and sediment cores, methyl parathion had half-lives of 77 to 154 hrs, while in a sterile control the half-life was 367 hrs(13), indicating that biodegradation is an important environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), methyl parathion, which has a vapor pressure of 3.5X10-6 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase methyl parathion is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 0.3 days(SRC), calculated from its rate constant of 5.9X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase methyl parathion may be removed from the air by wet and dry deposition(SRC). Methyl parathion absorbs light at wavelengths between 290 and 410 nm(4) and, therefore, may be susceptible to direct photolysis by sunlight(SRC).

Food Survey Values · 4 items

Methyl parathion was detected at concentrations ranging from 0.002 to 0.008 mg/kg in canned food and 0.003 to 0.007 mg/kg in fruit in New Zealand in 1974 and 0.018 to 0.029 mg/kg in leafy vegetables in Canada in 1972(1). In the Total Diet Program (US FDA, 1971-75) methyl parathion was detected in fruits, 0.007 mg/kg and leaf vegetables, trace to 0.010 mg/kg(1). In Market Basket Surveys (US FDA, 1966-69), methyl parathion was detected in leafy and stem vegetables at levels of 0 to >2.00 mg/kg and in root vegetables at levels of 0 to 1.00 mg/kg(1). Results of the FDA Total Diet Studies for fiscal years 1981-82: methyl parathion was detected in 4 of 327 food composites, collected from markets in 27 US cities, at levels ranging from 0.001 to 0.003 ppm, positive detections were in grain and cereal products, leafy vegetables, and root vegetable food groups(2). Methyl parathion was detected in 22 of 6,391 domestic agricultural commodities (celery, oranges, tangerines, alfalfa feed hay, iceburg lettuce, parsley, spinach) and in 67 of 12,044 imported agricultural commodities sampled by the U.S. FDA's Los Angeles District between Oct 1981 to Sept 1986(8). Methyl parathion was detected in peaches-apricots and lettuce in Rome, Italy at concentrations ranging (average) from less than or equal to 3.2 to 4.5 (2.5) ug/kg and less than 3.2 to 18 (3.6) ug/kg, respectively(4). Methyl parathion was detected in fresh carrots in Canada sampled between Jan 1992 and March 1994(5). It was detected in the following imported agricultural commodities in Canada sampled between Jan 1992 and March 1994: fresh apples, fresh grapes, fresh oranges, fresh pears, fresh snowpeas, and fresh tomatoes(5). Methyl parathion was detected in 8 of 234 ready-to-eat foods tested repetitively for 10 years, 1982 to 1991, through the US FDA's Revised Market Basket Survey at an average concentration of 0.0035 ug/g(6). In an FDA survey of domestic and imported pears (tomatoes) conducted between 1992 and 1993, methyl parathion was detected in 65 out of 710 domestic pears at a concentration of 0.09 ppm (1 out of 1,219 domestic tomatoes at trace concentrations) and in 4 out of 949 imported pears at a max concentration of 0.66 ppm (1 out of 144 imported tomatoes at a max concentration of 0.03 ppm)(7). In an FDA survey of domestic and imported apples (rice) conducted between 1993 and 1994, methyl parathion was detected in 72 out of 769 samples of domestic apples at a concentration of 0.15 ppm (4 out of 589 domestic rice samples at a max concentration of 0.13 ppm); it was detected in 4 out of 1,062 imported apples at a max concentration of 0.05 ppm (1 out of 612 imported rice samples at a max concentration of 0.04 ppm)(8).

Methyl parathion concentrations in seasonal vegetables collected directly from the field in the Agra District, India(1).

Methyl parathion in four fresh vegetables from three Chinese agricultural markets(1).

Methyl parathion was detected in 2 of 54 potato samples collected from Egyptian markets between March 1991 and Jan 1992 at concentrations of 0.389 and 0.540 ppm(1). Methyl parathion was detected in 40% of rice, 60% of avocados, 30% of strawberries, and 50% of tomatoes sampled in Mexico(2). Methyl parathion was detected in the following vegetables collected from growers' fields and main selling points in Pakistan between 1988 and 1992 (number of times detected and number of samples, concentration): luffa (turi) (1 of 11, 1.71 mg/kg), cauliflower (1 of 14, 2.5 mg/kg), spinach (1 of 16, 0.15 mg/kg), coriander (1 of 10, 1.5 mg/kg), bitter gourd (1 of 12, 4.0 mg/kg), fenugreek (1 of 8, 0.5 mg/kg), onion (3 of 18, 1.09 to 3.15 m/kg), and Lady's finger (4 of 28, 1.83 to 2.83 mg/kg)(3). Methyl parathion was detected in the following citrus fruits collected from the Valencian Community, Spain, between 1994 and 1995: Clementine 0.2 mg/kg, Navelate orange 0.3 to 0.5 mg/kg, Lanelate orange 0.1 to 1.1 mg/kg, Salustiana orange 0.5 to 3.8, Valencilate orange 0.3 to 0.9, and Star Ruby grapefruit 0.30(4). The compound was detected in citrus fruit in France at concentrations ranging from 0.003 to 1.25 ppm(5). Methyl parathion was detected in 26 of 2223 produce samples (700 vegetables and 1523 fruits) monitored in Sao Paulo City, Brazil, 1994-2001. The 26 positive samples included guava, lettuce, peach, and strawberry; range 0.10-0.41 ug/kg, mean of 0.15 ug/kg(6).

Regulatory information

RCRA Requirements · 1 item

P071; As stipulated in 40 CFR 261.33, when methyl parathion, as a commercial chemical product or manufacturing chemical intermediate or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to federal and/or state hazardous waste regulations. Also defined as a hazardous waste is any container or inner liner used to hold this waste or any residue, contaminated soil, water, or other debris resulting from the cleanup of a spill, into water or on dry land, of this waste. Generators of small quantities of this waste may qualify for partial exclusion from hazardous waste regulations (40 CFR 261.5(e)).

FIFRA Requirements · 5 items

The following uses of pesticide products containing the active ingredients specified below have been classified for restricted use and are limited to use by or under the direct supervision of a certified applicator.[Table#2927]

Tolerances are established for residues of the insecticide methyl parathion, including its metabolites and degradates, in or on the commodities in the table in this paragraph. Compliance with the tolerance levels specified in this paragraph is to be determined by measuring only methyl parathion, O,O-dimethyl O-(4-nitrophenyl) phosphorothioate, in or on the commodity.[Table#2928]

While petitions for tolerances for negligible residues are pending and until action is completed on these petitions, interim tolerances are established for residues of the listed pesticide chemicals in or on the following raw agricultural commodities:[Table#2929]

... EPA has completed its assessment of the cumulative risks from the organophosphate (OP) class of pesticides as required by the Food Quality Protection Act of 1996. In addition, the individual OPs have also been subject to review through the individual-chemical review process. The Agency's review of individual OPs has resulted in the issuance of Interim Reregistration Eligibility Decisions (IREDs) for 22 OPs /including methyl parathion/, interim Tolerance Reassessment and Risk Management Decisions (TREDs) for 8 OPs, and a Reregistration Eligibility Decision (RED) for one OP, malathion. ... EPA has concluded, after completing its assessment of the cumulative risks associated with exposures to all of the OPs, that: (1) the pesticides covered by the IREDs that were pending the results of the OP cumulative assessment ... are indeed eligible for reregistration; and (2) the pesticide tolerances covered by the IREDs and TREDs that were pending the results of the OP cumulative assessment ... meet the safety standard under Section 408(b)(2) of the FFDCA. Thus, with regard to the OPs, EPA has fulfilled its obligations as to FFDCA tolerance reassessment and FIFRA reregistration, other than product-specific reregistration.

For more FIFRA Requirements (Complete) data for METHYL PARATHION (6 total), please visit the HSDB record page.

CERCLA Reportable Quantities · 2 items

Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 100 lb or 45.5 kg. The toll free number of the NRC is (800) 424-8802. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b).

Releases of CERCLA hazardous substances are subject to the release reporting requirement of CERCLA section 103, codified at 40 CFR part 302, in addition to the requirements of 40 CFR part 355. Methyl parathion is an extremely hazardous substance (EHS) subject to reporting requirements when stored in amounts in excess of its threshold planning quantity (TPQ) of 100 or 10,000 lbs. Extremely hazardous substances that are solids are subject to either of two threshold planning quantities ... The lower quantity applies only if the solid exists in powdered form and has a particle size less than 100 microns; or is handled in solution or in molten form; or meets the criteria for a National Fire Protection Association (NFPA) rating of 2, 3 or 4 for reactivity. If the solid does not meet any of these criteria, it is subject to the upper ... threshold planning quantity ... .

Clean Water Act Requirements · 1 item

Methyl parathion is designated as a hazardous substance under section 311(b)(2)(A) of the Federal Water Pollution Control Act and further regulated by the Clean Water Act Amendments of 1977 and 1978. These regulations apply to discharges of this substance. This designation includes any isomers and hydrates, as well as any solutions and mixtures containing this substance.

State Drinking Water Guidelines · 4 items

(AZ) ARIZONA 1.8 ug/L

(CA) CALIFORNIA 2 ug/L

(FL) FLORIDA 10 ug/L

(ME) MAINE 2 ug/L

Federal Drinking Water GuidelinesEPA 1 ug/L

Chemistry & industry

Pharmacology

Mechanism of Action · 5 items

Acute poisoning ... is related to ... inhibiting action on enzyme acetylcholinesterase. Toxic manifestations generally occur only after more than 50% of plasma cholinesterase is inhibited.

... Methyl parathion ... depend on oxidative activation by replacement of thiono-sulfur with oxygen for ... toxicity.

Methyl parathion has only a slight inhibitory action on acetylcholinesterase and butyrylcholinesterase, but its active metabolite, methyl paraoxon, is a potent inhibitor of both these enzymes.

A study was conducted examining the inhibition of (Ca2+ and Mg2+)-ATPase by parathion (56382) and methyl parathion. Enzyme activity was assessed spectrophotometrically in pig erythrocyte membranes containing calcium2+ (Ca2+) and magnesium2+ and in solubilized membrane preparations incubated with the test agents. The enzyme response to ATP was biphasic. Equations expressing the kinetics of the substrate curves described two classes of the ATP binding active site, one with high affinity and low maximum rate and one with low affinity and high maximum rate. High affinity active sites were stimulated by low ATP concentrations (20 uM), whereas low affinity active sites were stimulated by high ATP levels (2 mM). Parathion and methylparathion dose dependently inhibited enzyme activity; parathion had a greater inhibitory effect than methylparathion. Lineweaver-Burke and Dixon plots indicated noncompetitive inhibition. Parathion and methylparathion induced enzyme inhibition occurred over a range of free calcium ion concentrations (0.5 to 5 mM); the inhibition was significantly greater at lower Ca2+ concentrations (1 to 100 uM) than at higher concentrations. The authors conclude that parathion and methylparathion inhibit ATPase activity by binding to a site on the enzyme rather than through an interaction with associated lipids.

For more Mechanism of Action (Complete) data for METHYL PARATHION (6 total), please visit the HSDB record page.

Biological Half-Life · 4 items

Adult hens were given oral daily doses of 2 mg (2 uC(i))/kg/day (14% of oral LD(50) in male rats) of [(14)C]methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate) for 10 consecutive days. ... Elimination of methyl parathion from plasma was monophasic with a terminal half-life of 17.5 hr, corresponding to an elimination rate constant of 0.039 ng/hr.

The half-life for methyl parathion was calculated to be 74 days at 25C and pH 7.

... The half-life of methyl parathion was 51 minutes ... /in adult female rats/.

The pharmacokinetics and placental transfer of a single dermal 10.0 mg (10uCi)/kg dose of uniformly phenyl-labeled [(14)C] methyl parathion (0,0-dimethyl 0-4-nitrophenyl phosphorothioate) were investigated in pregnant Sprague-Dawley rats at 14-18 days of gestation. Three rats were killed at each time interval: 1, 2, 4, 12, 24, 48, 72, and 96 hr after dosing. Radioactivity disappeared biexponentially from the administration sites, which retained 50% and 3% of the dose after 1 hr and 96 hr, respectively. Pharmacokinetic studies showed that methyl parathion disappeared monoexponentially from plasma and tissues. The half-life of elimination of methyl parathion from plasma was 11 hr corresponding to a constant rate value of 0.06 /per/ hr.

Metabolism/Metabolites · 6 items

The metabolism of ... methyl parathion has been extensively studied in a wide variety of organisms, incl microorganisms, plants, insects and mammals. ... /Its biotransformation/ depend on oxidative activation by replacement of thiono sulfur with oxygen for ... toxicity. Competing with this intoxication reaction are hydrolysis reactions that result in detoxification. The ring nitro group can also be reduced, particularly in bovine rumen fluid, to amino group; this results in amino parathion ... oxidative activation takes place primarily in liver. A number of ... /studies/ have shown that, in liver microsomal mixed function oxidase systems, presence of reduced nicotinamide adenine dinucleotide phosphate and oxygen are responsibe for this reaction. ... Degradative reactions that result in detoxification of ... methyl parathion involve either demethylation or dearylation. The resulting desmethyl compounds & dimethyl phosphoric acids are essentially nontoxic.

Methyl paraoxon may be metabolized by way of the same pathways as methyl parathion, resulting in the oxygen analogue ... /of O-methyl-O-para-nitrophenyl phosphate or dimethyl phosphoric acid, which require glutathione-dependent alkyl and aryl transferases, respectively/.

Effects of peppermint (Mentha piperita) and wild tomato (Lycopersicon hirsutum glabratum) on the toxicity, penetration and metabolism of methyl parathion were studied in larvae of the tobacco budworm, Heliothis virescens. Third-instar larvae fed wild tomato or peppermint leaves for 1 day were 3.3 and 2.7 times more tolerant to methyl parathion, respectively, as compared to insects fed an artificial diet. These tolerance levels were only 2.2 and 1.7 fold, respectively, in fifth-instar larvae when fed leaves of the same plant species for 1 day. Penetration studies did not indicate any difference in the rate of penetration of methyl parathion in larvae fed different diets. Methyl parathion injected into fifth-instar larvae was converted into 3 chloroform soluble and 5 water soluble metabolites. Five hr after injection, the extent of methyl parathion metabolism was greater in larvae fed wild tomato leaves (77.4%) or peppermint leaves (72.8%), than in those fed an artificial diet (64.55%). The major metabolite was p-nitrophenol and its formation was higher in larvae fed wild tomato leaves (49.4%) than in larvae fed peppermint leaves (44.23%), which in turn were higher than those fed an artificial diet (38.19%).

The role of human fetal liver glutathione S-transferases in the detoxification of methyl parathion was investigated. Glutathione S-transferases were partially purified by affinity chromatography utilizing reduced glutathione as the ligand coupled to epoxy-activated Sepharose 4B. This resulted in the isolation of material with an average activity (mean + or - SE ) of 58.90 + or - 4.83 mu mol 1-chloro-2,4-dinitrobenzene conjugate formed/min/mg, representing a purification of 70 fold. These partially purified fetal liver transferase catalyzed the metabolism of methyl parathion exclusively to desmethyl parathion via O-dealkylation. High-performance liquid chromatography, radiometric analysis of the enzymic reaction, and co-chromatography with reference standard on thin-layer chromatography confirmed the sole metabolite as desmethyl parathion. The range of fetal liver activity towards methyl parathion was from 30 to 122 mmol desmethyl parathion formed/min/mg. Analysis of the kinetic parameters of three partially purified fetal liver preparations with gestational ages of 14, 16 and 21 weeks resulted in Km values for methyl parathion of 0.24, 0.38, and 0.86 mM, respectively; whereas, the Km values assessed for glutathione were 0.20, to 0.10 and 0.18 mM. The ability of human fetal liver glutathione S-transferases to catalyze the metabolism of methyl parathion exclusively to desmethyl parathion via O-dealkylation represents a major qualitative biochemical difference from the rat liver isozymes.

For more Metabolism/Metabolites (Complete) data for METHYL PARATHION (16 total), please visit the HSDB record page.

Metabolism of organophosphates occurs principally by oxidation, by hydrolysis via esterases and by reaction with glutathione. Demethylation and glucuronidation may also occur. Oxidation of organophosphorus pesticides may result in moderately toxic products. In general, phosphorothioates are not directly toxic but require oxidative metabolism to the proximal toxin. The glutathione transferase reactions produce products that are, in most cases, of low toxicity. Paraoxonase (PON1) is a key enzyme in the metabolism of organophosphates. PON1 can inactivate some organophosphates through hydrolysis. PON1 hydrolyzes the active metabolites in several organophosphates insecticides as well as, nerve agents such as soman, sarin, and VX. The presence of PON1 polymorphisms causes there to be different enzyme levels and catalytic efficiency of this esterase, which in turn suggests that different individuals may be more susceptible to the toxic effect of organophosphate exposure.

MeSH Pharmacological Classification · 2 items

Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system.

Pesticides designed to control insects that are harmful to man. The insects may be directly harmful, as those acting as disease vectors, or indirectly harmful, as destroyers of crops, food products, or textile fabrics.

Absorption, Distribution and Excretion · 5 items

... Absorbed into body by respiratory, gastrointestinal, & cutaneous pathways.

Methyl parathion is readily absorbed through the skin, mucous membranes, and eyes which presents a potentially great danger from these avenues of absorption.

Only tissue accumulation ... observed is irreversible binding to esterase enzymes. Highest concn are in liver & lung.

Nitrophenolic and alkyl phosphate metabolites of methyl and ethyl parathion in the urine of human subjects soon after doses of 1 to 4 mg have been ingested. Particular alkyl phosphates can serve as specific indices of absorption of the respective parathions. Paranitrophenol and diethyl thiophosphate are rapidly eliminated in the urine, while excretions of dimethyl phosphate, and particularly diethyl phosphate, are more protracted. Cumulative excretions of paranitrophenol and alkyl phosphates exhibit sufficient dose-dependence at convenient intervals following parathion ingestion to encourage use of metabolite measurements in estimating occupational absorption of the parathion insecticides.

For more Absorption, Distribution and Excretion (Complete) data for METHYL PARATHION (15 total), please visit the HSDB record page.

Uses & manufacturing

Uses · 5 items

Used to kill boll weevils on cotton; [EXTOXNET]

Farming (Pesticides) [Category: Industry]

For methyl parathion (USEPA/OPP Pesticide Code: 053501) ACTIVE products with label matches. /SRP: Registered for use in the USA but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

Insecticide

Methyl parathion is an insecticide. It is used to kill insects on farm crops, especially cotton. (L634)

Impurities · 1 item

Following impurities ... identified in ... sample of technical grade methyl parathion: O,O-dimethyl S-methyl dithiophosphate; nitroanisole; nitrophenol; isomers of methyl parathion and the dithio analog of methyl parathion. /Technical grade methyl parathion/

U.S. Exports · 4 items

(1972) 5.68X10+9 G

(1984) 3.01X10+9 g

(1987) 5.31X10+4 lb

(1987) 3.25X10+5 lb (Methyl parathion preparations)

U.S. Imports · 2 items

(1972) 4.99X10+8 G

(1975) 4.01X10+7 G

U.S. Production · 2 items

(1972) 2.3X10+10 G

(1975) 2.44X10+10 G

Consumption Patterns · 5 items

83% For cotton; 8% for soybeans; 2% for wheat; 5% for other grain crops including corn; 2% for ornamentals and misc agricultural commodities including tobacco, peanuts, alfalfa, assorted vegetables, and citrus fruits (1971)

Applied to alfalfa, 15.6%; Artichokes, 7.5%; Cotton, 7.8%; Lettuce, 7.9%; Onions, 3%; Rice, 32%; Sugarbeets, 7.4%; Tomatoes, 8.1%; Most of remainder applied to vegetable crops (1984); /California use, calculated from table/ (1984) 1.04X10+6 g /Used in California/

Use of methyl parathion on rice in CA by year: 39,300 kg in 1980, 46,400 kg in 1982, 33,400 kg in 1984, 22,100 in 1986, 32,500 in 1988, 24,500 in 1990, 15,600 in 1992, and 23,000 in 1993.

The following crops were treated with methyl parathion in the United States during the 1989 to 1991 crop years (from federal and state pesticide surveys of insecticide use patterns), percent of national acreage of each crop treated: alfalfa 2%, apples 24%, artichokes 4%, barley <1%, broccoli 1%, brussel sprouts 13%, cabbage 1%, cantaloupes 2%, carrots 4%, cauliflower 1%, celery 2%, cherries 2%, collards 12%, corn 2%, cotton 24%, cucumbers <1%, dry beans 5%, dry peas <1%, grapes 3%, green beans 3%, green peas <1%, hops 4%, lettuce 4%, nectarines 1%, oats <1%, onions 24%, other hay <1%, peaches 13%, peanuts 1%, pears 3%, pecans 4%, plums 1%, potatoes <1%, rice 16%, rye <1%, soybeans 2%, spinach 5%, strawberries 1%, sugarbeets 1%, sunflowers 40%, sweet corn 18%, sweet peppers 1%, tomatoes 1%, watermelons 6%, and wheat 2%.

Methyl parathion's use in U.S. agriculture in 1966, 1971, 1976, 1982, and 1989 was 8,002,000, 27,563,000, 23,350,000, 11,335,000, and 7,652,000 lbs AI/year, respectively.

General Manufacturing Information · 5 items

The WHO Recommended Classification of Pesticides by Hazard identifies methyl-parathion (technical grade) as Class IA: extremely hazardous; Main Use: insecticide.

Pesticides subject to the Rotterdam Convention. Class: Ia; Pesticide: Methyl-parathion (emulsifiable concentrates (EC) with 19.5%, 40%, 50%, 60% active ingredient and dusts containing 1.5%, 2% and 3% active ingredient. (According to the Rotterdam Convention, export of a chemical can only take place with the prior informed consent of the importing Party. The Prior Informed Consent (PIC) procedure is a means for formally obtaining and disseminating the decisions of importing countries as to whether they wish to receive future shipments of a certain chemical and for ensuring compliance to these decisions by exporting countries. The aim is to promote a shared responsibility between exporting and importing countries in protecting human health and the environment from the harmful effects of such chemicals ... The Rotterdam Convention (which entered into force on 24 February 2004) built on the voluntary PIC procedure which was initiated by UNEP /United Nations Environment Programme/ and FAO /Food and Agriculture Organization of the United Nations/ 1989.)

Non-systemic contact and stomach insecticide with some respiratory action. Acaricidal side-effects

Methyl parathion was applied in emulsifiable concentrate formulation, wettable powder, and encapsulated formulation all prepared from 1.25% active ingredient field strength concn to unfinished 50% cotton/50% polyester bottom weight poplin fabric, and durable press finished and stain resistant fabrics of the same blend. In a second experiment, emulsifiable concentrate, encapsulated formulation, or wettable powder formulations of methyl parathion at 1.25% active ingredient were applied to a nylon surface. The fabrics were laundered in a home washing machine in nonionic or standard ... detergent at 140 °C or 49 °F and the spreading of methyl parathion residues was measured by extracted samples subjected to gas chromatography. Contamination before laundering was significantly lower for the stain resistant finished fabric than for the unfinished fabric or durable press finished fabric. Laundering significantly reduced methyl parathion levels in the specimens. No significant differences were found between detergent type or washing temperatures. Residues after laundering were markedly lower when encapsulated formulation had been used to contaminate the fabric than when emulsifiable concentrate was the formulation. Significant differences in pesticide contamination attributable to fabric finish of specimens were observed, with the greatest amount found in the unfinished fabric, followed by the durable press finished fabric and then by stain resistant finished fabrics. Levels of methyl parathion were greatest at the initial site of contamination and in the first concentric ring, a distance of approximately 2 cm from the site of initial contamination.

For more General Manufacturing Information (Complete) data for METHYL PARATHION (6 total), please visit the HSDB record page.

Related reactions

0 records

New reaction record

No reaction records under the current filter.

Linked notes

Loading…

Basic information