Carbaryl

Description

Carbaryl is a colourless to light tan or white or grey solid crystal depending on the purity of the compound. The crystals are essentially odourless and stable to heat, light, and acids but are not stable under alkaline conditions. It is non-corrosive to metals, packaging materials, and application equipment. Carbaryl is classified as a general use pesticide (GUP). It is sparingly soluble in water, but soluble in dimethylformamide, dimethyl sulfoxide, acetone, cyclohexanone, isopropanol, and xylene. Carbaryl is a wide-spectrum carbamate insecticide, which controls over 100 species of insects on citrus, fruit, cotton, forests, lawns, nuts, ornamentals, shade trees, and other crops, as well as on poultry, livestock, and pets. It is also used as a molluscicide and an acaricide. Carbaryl works whether it is ingested into the stomach of the pest or absorbed through direct contact. It is available as bait, dusts, wettable powders, granules, dispersions, and suspensions.

Chemical Properties

Carbaryl is a colorless to light tan or white or gray, solid crystals depending on the purity of the compound. The crystals are essentially odorless, and stable to heat, light, and acids, but are not stable under alkaline conditions. It is non-corrosive to metals, packaging materials, and application equipment. Carbaryl is classifi ed as a GUP. It is sparingly soluble in water, but soluble in dimethylformamide, DMSO, acetone, cyclohexanone, isopropanol, and xylene. Carbaryl is a wide-spectrum carbamate insecticide that controls over 100 species of insects on citrus, fruit, cotton, forests, lawns, nuts, ornamentals, shade trees, and other crops, as well as on poultry, livestock, and pets. It is also used as a molluscicide and an acaricide. Carbaryl works whether it is ingested into the stomach of the pest or absorbed through direct contact. It is available as bait, dusts, wettable powders, granules, dispersions, and suspensions

Chemical Properties

colourless solid

Physical properties

White to light tan crystals with a bleach-like type odor. At 40 °C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 280 and 37 μg/L, respectively. At 25 °C, the average taste threshold concentration and the lowest concentration at which a taste was detected were 140 and 44 μg/L, respectively (Young et al., 1996).

Physical properties

White to light tan crystals with a bleach-like type odor. At 40°C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 280 and 37 μg/L, respectively. At 25°C, the average taste threshold concentration and the lowest concentration at which a taste was detected were 140 and 44 μg/L, respectively (Young et al., 1996).

Uses

Labelled Prifinium Bromide, a synthetic antispasmodic drug; parasympatholytic. Prifinium Bromide is used as a quartenary anticholinergic agent.

Uses

Contact insecticide.

Uses

Contact insecticide used to control most insects on fruits, vegetables and ornamentals

Uses

Carbaryl is a pesticide, an insecticide of the carbamate group. It induced sensitization in a farmer.

Uses

Cholinesterase inhibitor. Ectoparasiticide.

Definition

ChEBI: A carbamate ester obtained by the formal condensation of 1-naphthol with methylcarbamic acid.

Indications

Carbaryl (Sevin), a cholinesterase inhibitor insecticide, is used as a pediculicide in the form of a shampoo. This product has an objectionable odor, but has some ovicidal activity. It is an effective medication available in England and some other countries but not in the United States.

General Description

A white crystalline solid. Insoluble in water. Combustible, although difficult to ignite. Toxic by inhalation (dust, etc.). Produces toxic oxides of nitrogen during combustion.

Air & Water Reactions

Slightly soluble in water.

Reactivity Profile

Carbaryl is a carbamate ester. Carbamates are chemically similar to, but more reactive than amides. Like amides they form polymers such as polyurethane resins. Carbamates are incompatible with strong acids and bases, and especially incompatible with strong reducing agents such as hydrides. Flammable gaseous hydrogen is produced by the combination of active metals or nitrides with carbamates. Strongly oxidizing acids, peroxides, and hydroperoxides are incompatible with carbamates. Carbaryl is unstable in an alkaline media. . Carbaryl is incompatible with the following: Strong oxidizers, strongly alkaline pesticides .

Hazard

Toxic by ingestion, inhalation, and skin absorption; irritant. A reversible cholinesterase inhibitor. Use may be restricted. Questionable car- cinogen. Male reproductive and embryo damage.

Health Hazard

Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Health Hazard

Acute oral toxicity — moderate in rats; dermal toxicity low to very low; oral LD50 value(rats); 250 mg/kg, skin LD50 value (rats);4000 mg/kg; toxic symptoms in humans —nausea, vomiting, diarrhea, abdominal cramps,miosis, lachrimation, excessive salivation,nasal discharge, sweating, cyanosis, muscletwitching, convulsions, and coma; acetylcholinesterase inhibitor; exposure limit: TLVTWA 5 mg/m³ (ACGIH, OSHA, and MSHA).
The poisoning effects from carbaryl takeplace very quickly, but lasts only for a shorttime. It is readily hydrolyzed to 1-naphtholwhich is excreted. Although its toxicity inhumans is relatively low, the compound canproduce strong effect on bees and aquaticspecies even in small quantities.

Health Hazard

Exposures to carbaryl cause a moderate to very toxic health disorder among workers. Carbaryl produces adverse effects in humans by skin contact, inhalation, or ingestion. The symptoms of acute toxicity are typical of the other carbamates. Direct contact of the skin or eyes with moderate levels of this pesticide can cause burns. Inhalation or ingestion of very large amounts can be toxic to the nervous and respiratory systems, resulting in nausea, stomach cramps, diarrhea, and excessive salivation. Exposures to high concentrations of carbaryl causes poisoning with symptoms such as excessive sweating, headache, weakness, giddiness, nausea, vomiting, stomach pains, blurred vision, slurred speech, muscle twitching, incoordination, and convulsions. The effects of carbaryl on the nervous system of rats, chickens, monkeys, and humans are primarily related to the inhibition of AChE that under normal situations is transitory. The only documented fatality from carbaryl was through intentional ingestion. Laboratory studies have indicated that the acute oral toxicity (LD50) of carbaryl ranges from 250 to 850 mg/kg in rats, and from 100 to 650 mg/kg in mice. The inhalation toxicity (LC50) in rats is greater than 206 mg/L. Low doses of carbaryl cause minor skin and eye irritation in rabbits. The acute dermal toxicity (LD50) of carbaryl to rabbits is measured as greater than 2000 mg/kg. In a 90-day feeding study, carbaryl did not cause any signifi cant adverse effects in rats. Carbaryl in high doses has caused no reproductive or fetal effects in a long-term feeding study of rats. Ingestion of carbaryl affected the lungs, kidneys, and liver of experimental animals. Inhalation of carbaryl caused adverse effect to the lungs. High doses of carbaryl for a prolonged period caused nerve damage in rats and pigs. Several studies indicate that carbaryl can affect the immune system in animals and insects. The evidence for teratogenic effects due to chronic exposure is minimal in test animals. Birth defects in rabbit and guinea pig offspring occurred only at dosage levels that were highly toxic to the mother.

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Containers may explode when heated. Runoff may pollute waterways.

Agricultural Uses

Insecticide, Nematicide, Plant growth regulator: Carbaryl is one of the most widely used insecticides in agriculture, professional turf management and ornamental production, as well as in residential pet, lawn, and garden markets. It controls over 100 species of insects that infect citrus, cotton, nuts, and forest and ornaments trees, as well as poultry and livestock. Carbaryl also is used as a mosquito adulticide. It is available in a variety of formulations bait, dust, wettable powders, granules, dispersions and suspensions. Washington State, for example, has a Special Local Needs registration to control burrowing shrimp in oyster beds. A U.S. EPA restricted Use Pesticide (RUP). Banned for use in EU countries.

Trade name

ADIOS®; ARILAT®; ARILATE®; ARYLAM®; BERCEMA NMC50®; BUGMASTER®[C]; CAPROLIN®; CARBAMEC®; CARBAMINE®; CARBATOX®; CARBAVUR®; CARBOMATE®; CARPOLIN®; COMPOUND 7744®; CARYLDERM®; CRAG SEVIN®; CRUNCH®; DENAPON®; DICARBAM®; DYNA-CARBYL®; EXPERIMENTAL INSECTICIDE 7744®; GAMONIL®; GERMAIN'S®; HEXAVIN®; KARBASPRAY®; KARBATOX®; KARBOSEP®; MENAPHAM®; MICROCARB®; MUGAN®; MURVIN®; NAC®; NMC® 50; OMS29®; OMS 629®; OLTITOX®; PANAM®; POMEX®; PROSEVOR® 85; RAVYON®; SAVIT®[C]; SEPTENE®; SEFFEIN®; SEVIMOL®; SEVIN®; SEWIN®; SOK®; TERCYL®; THINSEC®; TORNADO®; TRICAR®; UNION CARBIDE 7,744®; VIOXAN®

Contact allergens

Carbaryl is a pesticide and insecticide of the carbonate group. It induced sensitization in a farmer.

Safety Profile

Poison by ingestion, intravenous, intraperitoneal, and possibly other routes. Human systemic effects by ingestion: sensory change involving peripheral nerves and muscle weakness. Experimental teratogenic and reproductive effects. Questionable carcinogen with experimental carcinogenic and tumorigenic data. Human mutation data reported. An eye and severe skin irritant. Absorbed by all routes, although skin absorption is slow. No accumulation in tissue. Symptoms include blurred vision, headache, stomachache, vomiting. Symptoms sirmlar to but less severe than those due to parathion. A reversible cholinesterase inhibitor. See also CARBAMATES and ESTERS. When heated to decomposition it emits toxic fumes of NOx

Potential Exposure

Carbaryl is a white or grayish, odorless, crystalline solid; or various other forms including liquid and paste. Molecular weight 5 201.24; boiling point 5 (decomposes below BP); freezing/melting point 5 142C; vapor pressure 5, 4 3 1025 mmHg @ 25C; flash point 5B200C. Hazard identification (based on NFPA- 704 M Rating System): Health 3, flammability 1, reactivity 0. Practically insoluble in water; solubility 5 0.02 g/L @ 30C

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contactsthe skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove fromexposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing hasstopped and CPR if heart action has stopped. Transferpromptly to a medical facility. When this chemical hasbeen swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Carcinogenicity

Carbaryl is not considered to be genotoxic.

Environmental Fate

Biological. Fourteen soil fungi metabolized methyl-14C-labeled carbaryl via hydroxylation to 1-naphthyl-N-hydroxymethylcarbamate, 4-hydroxy-1-naphthylmethylcarbamate and 5-hydroxy-1-naphthylmethylcarbamate (Bollag and Liu, 1972). Carbaryl was degraded by a culture of Aspergillus terreus to 1-naphthylcarbamate. The half-life was 8 days (Liu and Bollag, 1971a).
Various microorganisms isolated from soil hydrolyzed carbaryl to 1-napthol. For example, Fusarium solani degraded carbaryl 82% after 12 days at a temperature of 26–28°C (Bollag and Liu, 1971).
In a small watershed, carbaryl was applied to corn seed farrows at a rate of 5.03 kg/ha active ingredient. Carbaryl was stable up to 166 days, but after 135 days, 95% had disappeared. The long lag time suggests that carbaryl degradation was primarily due to microbial degradation (Caro et al., 1974).
Soil. The rate of hydrolysis of carbaryl in flooded soil increased when the soil was pretreated with the hydrolysis product, 1-naphthol (Rajagopal et al., 1986). Carbaryl is hydrolyzed in both flooded and nonflooded soils but the rate is slightly higher under flooded conditions (Rajagopal et al., 1983). When 14C-carbonyl-labeled carbaryl (200 ppm) was added to five different soils and incubated at 25°C for 32 days, evolution of 14Ccarbon dioxide varied from 2.2–37.4% (Kazano et al., 1972). Metabolites identified in soil included 1-naphthol (hydrolysis product) (Sud et al., 1972; Ramanand et al., 1988a), hydroquinone, catechol, pyruvate (Sud et al., 1972), coumarin, carbon dioxide (Kazano et al., 1972), 1-naphthylcarbamate, 1-naphthyl N-hydroxymethylcarbamate, 5-hydroxy-1-naphthylmethylcarbamate, 4-hydroxy-1-naphthylmethylcarbamate and 1-naphthyl hydroxymethylcarbamate (Liu and Bollag, 1971, 1971a). 1-Naphthol was readily degraded by soil microorganisms (Sanborn et al., 1977).
When carbaryl was applied to soil at a rate of 1,000 L/ha, more than 50% remained in the upper 5 cm (Meyers et al., 1970). The half-lives of carbaryl in a sandy loam, clay loam and an organic amended soil under non-sterile conditions were 96–1,462, 211–2,139 and 51–4,846 days, respectively, while under sterile conditions the half-lives were 67–5,923, 84–9,704 and 126–4,836, respectively (Schoen and Winterlin, 1987).
Liu and Bollag (1971) reported that the fungus Gliocladium roseum degraded carbaryl to 1-naphthyl N-hydroxymethylcarbamate, 4-hydroxy-1-naphthylmethylcarbamate and 1- naphthylhydroxymethylcarbamate.
Sud et al. (1972) discovered that a strain of Achromobacter sp. utilized carbaryl as the sole source of carbon in a salt medium. The organism grew on the degradation products 1-naphthol, hydroquinone and catechol. 1-Naphthol, a metabolite of carbaryl in soil, was recalcitrant to further degradation by a bacterium tentatively identified as an Arthrobacter sp. under anaerobic conditions (Ramanand et al., 1988a). Carbaryl or its metabolite 1- naphthol at normal and ten times the field application rate had no effect on the growth of Rhizobium sp. or Azotobacter chroococcum (Kale et al., 1989). The half-lives for carbaryl under flooded and nonflooded conditions were 13–14 and 23–28 days, respectively (Venkateswarlu et al., 1980).
Rajagopal et al. (1984) identified the following degradates of carbaryl in soil and in microbial cultures: 5,6-dihydrodihydroxy carbaryl, 2-hydroxy carbaryl, 4-hydroxy carbaryl, 5-hydroxy carbaryl, 1-naphthol, N-hydroxymethyl carbaryl, 1-naphthyl carbamate, 1,2-dihydroxynaph-thalene, 1,4-dihydroxynaphthalene, o-coumaric acid, o-hydroxybenzalpyruvate, 1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, coumarin, γ-hydroxy-γ-ohydroxyphenyl-α-oxobutyrate, 4-hydroxy-1-tetralone, 3,4-di-hydroxy-1-tetralone, pyruvic acid, salicylaldehyde, salicylic acid, phenol, hydroquinone, catechol, carbon dioxide and water. When carbaryl was incubated at room temperature in a mineral salts medium by soil-enrichment cultures for 30 days, 26.8 and 31.5% of the applied insecticide remained in flooded and nonflooded soils, respectively (Rajagopal et al., 1984a). A Bacillus sp. and the enrichment cultures both degraded carbaryl to 1-naphthol. Mineralization to carbon dioxide was negligible (Rajagopal et al., 1984a).

Metabolic pathway

The metabolism of carbaryl has been extensively reviewed many times and so original research papers are not generally quoted. Pathways for carbaryl include hydroxylation of the aromatic ring and the methyl group, carbamate ester hydrolysis and conjugation. The metabolism of carbaryl has been extensively reviewed by Schlagbauer and Schlagbauer (1972), Fukuto (1972), Kuhr and Dorough (1976), Mount and Oehme (1981) and by the WHO (1994). Metabolism in man was reviewed by Hutson (1981) and in economic animals by Akhtar (1985).

Metabolism

Carbaryl undergoes hydrolysis and ring oxidation in soils. The major metabolite in a number of studies was 1-naphthol. Metabolites also included 4-hydroxycarbaryl and 5-hydroxycarbaryl. In mammals, the major metabolite is 1-naphthol. This is eliminated in urine and feces, together with the glucuronic acid conjugate. Aromatic ring hydroxylation at the 3-, 4-, 5-, or 6- positions also occurs as does hydroxylation at the N-methyl group.

storage

Color Code—Blue: Health Hazard: Store in asecure poison location. Prior to working with carbaryl youshould be trained on its proper handling and storage. Storein tightly closed containers in a cool, well-ventilated area.Carbaryl must be stored to avoid contact with strong oxidizers (such as chlorine, bromine, and fluorine) since violentreactions occur. Sources of ignition, such as smoking andopen flames, are prohibited where carbaryl is used, handled,or stored in a manner that could create a potential fire orexplosion hazard.

Shipping

UN2757 Carbamate pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials. UN 2811 Toxic solids, organic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required

Degradation

Carbaryl is stable in neutral and weakly acidic media but hydrolysed under basic conditions (PM).
Hydrolysis in natural waters is mostly chemical, usually with a half-life of a few days or less. Carbaryl undergoes base-catalysed hydrolysis to form 1-naphthol(2) and N-methylcarbamic acid (3) which decomposes to methylamine and CO2 (see Scheme 1). No other degradation product accounted for more than 2% of the applied dose and no volatile products were detected during hydrolysis (WHO, 1994). Carbaryl is not rapidly photodegraded in the field. In basic solutions exposed to light, the dissociated form of 1-naphthol (2) (1-naphthoxide ion) was transformed to 2-hydroxy-1,4-naphthoquinone (4) as confirmed by MS (Kuhr and Dorough, 1976). Photodecomposition accounted for some loss of carbaryl in clear surface waters exposed to sunlight for long periods but this was not a major route of degradation. Cleavage of the ester bond was the main photo-reaction, but in organic solvents other reactions can occur to give small amounts of naphthamides, naphthalene and β-naphthyl-1-naphthol. l-Naphthol (2) was photodecomposed faster than carbaryl (WHO, 1994).
An aqueous photolysis study was conducted under conditions relevant to decontamination rather than to the natural environment. Aqueous solutions of carbaryl containing a dispersion of TiO2 were irradiated with a xenon lamp, with a cut-off filter at 340 nm, at 55 °C. Solutions were extracted and analysed by HPLC or GC-MS methods. Parent carbaryl degraded within 30 minutes at pH 3, 6 or 9. It was suggested that the initial step was attack by hydroxyl radical. The N-methylcarbamoyl moiety was cleaved and hence no carbamate products were identified. Pathways involved hydroxylation of the ring and oxidation of dihydroxy derivatives to form quinones (see Scheme 1). Intermediates identified included 1,2-, 1,3- and 1,4-dihydroxybenzenes (5, 6 and 7), 1,2,3- trihydroxybenzene (8), dihydroxynaphthalene (9), 1,4-naphthaquinone (10), 2- and 5-hydroxynaphthaquinone (4 and 11), other hydroxynaphtha-lenediones (12) and a small proportion of 1,3-indandione (13)(Pramauro et al., 1997).

Toxicity evaluation

Carbaryl is soluble in organic solvents (e.g., dimethyl formamide, acetone) and is moderately soluble in water (32 mg l^-1 solubility at 20°C). The calculated Henry’s law constant of 0.000000003 atm m3 mol l^-1 indicates that surface water volatilization is unlikely an important fate process. The estimated half-life for reacting with airborne photochemically generated hydroxyl radicals is 12.6 h. Photolysis produces naphthoquinone products.
Carbaryl undergoes abiotic hydrolysis, photodegradation, and biotic degradation in soil and water. Depending on soil type and climate, its soil persistence varies from 13 days to 2 years. Half-lives in canal and river waters vary from 4 to 30 days, hydrolysis rate is greater with increasing temperature and alkalinity. Carbaryl can persist for years under acidic environments. The estimated log Koc of 1.87–2.46 indicates moderate adsorption to soil and the potential for groundwater leaching.

Incompatibilities

Contact with strong oxidizers can cause fire and explosions.

Waste Disposal

Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed. Submit to alkaline hydrolysis before disposal.