Dichlorvos

Description

Cases of sensitization to dichlorvos have been seen in chrysanthem growers, horticulturists, technicians and in a chemist.

Description

Dichlorvos is an organophosphate insecticide and inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE; IC₅₀s = 269 and 44 nM, respectively). It also binds to the M₂ muscarinic receptor in rat heart homogenates. Dichlorvos is lethal to 4-week old German cockroach (B. germanica) nymphs (LD₅₀ = 0.108 μg per insect) and silkworms (B. mori) in third instar (LC₅₀ = 6.63 mg/L) after 24 hours. It is lethal to zebrafish (D. rerio) embryos (LC₅₀ = 39.75 mg/L after 24 hours) and decreases swimming activity of larvae 6 days after fertilization when administered at a concentration of 25 mg/L in tank water. Dichlorvos (150 ppm for 80 weeks) also increases the incidence of benign and malignant neoplasms in male rats from 47 to 88% as compared to controls.

Chemical properties

Dichlorvos is available as an oily colourless to amber liquid with an aromatic chemical odour. It is slightly soluble in water but soluble in kerosene, ethanol, chloroform, and acetone and miscible with alcohol, aromatic and chlorinated hydrocarbon solvents, aerosol propellants, and other non-polar solvents. Dichlorvos in contact with strong acids or alkalis undergoes decomposition and releases hazardous products toxic gases and vapours such as phosphorus, chlorinated oxides, and carbon monoxide.

Chemical properties

Dichlorvos occurs as an oily colorless to amber liquid with slight solubility in water. It has an aromatic chemical odor. Dichlorvos is used as an agricultural insecticide for the control of crop pests, such as fl ies, aphids, spider mites, caterpillars, and thrips, and also pests in store grains, and parasitic worms in animals, in fl ea collars for dogs. Occupational workers and the general public can be exposed to dichlorvos while working with the manufacture, formulation, and application on agricultural crops, and when used as a fumigant, and as pest strips. Human exposures also occur through food contamination.

Chemical properties

Dichlorvos is a colorless to amber liquid with a mild aromatic odor.

Physical properties

Colorless to yellow liquid with a mild aromatic odor

The Uses of Dichlorvos

Dichlorvos is used for the control of household and public health insect pests and the control of sucking and chewing pests in a wide range of crops. It is used as a veterinary anthelmintic, as an ectoparasiticide on fish and domestic pets and a vapour phase domestic insecticide as well for the control of phorid and sciarid flies in mushroom compost.

The Uses of Dichlorvos

Cholinesterase inhibitor. Anthelmintic, insecticide.

The Uses of Dichlorvos

anesthetic

The Uses of Dichlorvos

Organophosphorus insecticide and fumigant used against flies, mosquitoes and moths.

What are the applications of Application

Dichlorvos is a cholinesterase inhibitor

Definition

ChEBI: An alkenyl phosphate that is the 2,2-dichloroethenyl ester of dimethyl phosphate.

brand name

Atgard (Boehringer Ingelheim Animal Health); Equigard (Boehringer Ingelheim Animal Health); Equigel (Boehringer Ingelheim Animal Health); TASK Tabs (Boehringer Ingelheim Animal Health).

General Description

An aromatic colorless to amber liquid absorbed in a dry carrier. Denser than water and slightly soluble in water. Toxic by inhalation, skin absorption, absorption, or ingestion. Flash point 175°F or higher. When heated to high temperatures may emit toxic chloride fumes and phosgene gas. Used as a pesticide.

Air & Water Reactions

Slightly soluble in water.

Reactivity Profile

DICHLORVOS MIXTURE is incompatible with strong acids and bases. Dichlorvos is slowly hydrolyzed in acidic media and rapidly hydrolyzed by alkalis. Dichlorvos is corrosive to iron and mild steel. . Organophosphates are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides.

Health Hazard

Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Contact with molten substance may cause severe burns to skin and eyes. 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

Highly toxic by all routes of exposure;exhibits acute, delayed, and chronic poison-ing; cholinesterase inhibitor; signs and symp-toms of exposure are similar to those ofother organophosphates; toxic effects includesweating, twitching of muscle, constrictionof pupils, lacrimation, salivation, tightnessin the chest, wheezing, slurred speech, nau-sea, vomiting, abdominal pain, and diarrhea;high exposure can result in coma, cessationof breathing, and death. Oral LD50 valuein rodents reported in the literature varieswidely from 17 to 80 mg/kg in rat and61–275 mg/kg in mouse.
LC50 inhalation (mouse): 13 mg/m³ /4 h
LD50 skin (mouse): 206 mg/kg
LD50 oral (wild bird): 12 mg/kg.

Health Hazard

Exposures to dichlorvos through all routes, namely, oral, dermal, and respiratory, cause adverse effects to species of laboratory animals, such as rats, mice, and rabbits. The symptoms of poisoning include perspiration, nausea, salivation, vomiting, diarrhea, drowsiness, fatigue, headache, and in severe cases, tremors, ataxia, convulsions, and coma.
Humans exposed to dichlorvos show many symptoms of poisoning that include, but are not limited to, irritability, confusion, headache, speech diffi culties, sweating, blurred vision, drowsiness or insomnia, numbness, tingling sensations, incoordination, tremor, abdominal cramps, diffi culty in breathing or respiratory depression and slow heart beat, impaired memory concentration, disorientation, and severe depressions.

Fire Hazard

Combustible material: may burn but does not ignite readily. Containers may explode when heated. Runoff may pollute waterways. Substance may be transported in a molten form.

Agricultural Uses

Insecticide, Acaricide, Nematicide: Dichlorvos is used for insect control in food-storage areas, green-houses, and barns, and control of insects on livestock. It is not generally used on outdoor crops. Dichlorvos is sometimes used for insect control in workplaces and in the home. Dichlorvos used in pest control is diluted with other chemicals and used as a spray. It can also be incorporated into plastic that slowly releases the chemical. Veterinarians use it to control parasites on pets. Dichlorvos is effective against mushroom flies, aphids, spider mites, caterpillars, thrips, and white flies in greenhouse, outdoor fruit, and vegetable crops. It is used to treat a variety of parasitic worm infections in dogs, livestock, and humans. Dichlorvos can be fed to livestock to control botfly larvae in the manure. It acts against insects as both a contact and a stomach poison. It is used as a fumigant and has been used to make pet collars and pest strips. It is available as an aerosol and soluble concentrate. Not approved for use in EU countries. A U.S. EPA restricted Use Pesticide (RUP). Dichlorvos also exists as a breakdown product.

Trade name

ALCO® Dichlorvos; APAVAP®; ASTROBOT®; ATGARD®; BAY 19149®; BAYER 19149®; BENFOS®; BIBESOL®; BREVINYL®; BREVINYL E 50®; CANOGARD®; CEKUSAN®; CYPONA®; DEDEVAP®; DERRIBAN®; DERRIBANTE®; DES®; DEVIKOL®; DICLORCAL 50®; DIDIVANE; DIVIPAN®; DOOM®; DQUIGARD®; DUO-KILL®; DURAVOS®; ELASTREL®; EQUIGARD®[C]; EQUIGEL®[C]; ESTROSEL®; ESTROSOL®; FECAMA®; FEKAMA®; FLY-DIE®; FLY FIGHTER®; HERKOL®; INSECTIGAS D®; KRECALVIN®; LINDAN®; MAFU®; MARVEX®; MOPARI®; NEFRAFOS®; NERKOL®; NOGOS®; NOPEST®; NOVOTOX®; NUVA®; NUVAN®; OKO®; OMS 14®; PANAPLATE®; PHOSVIT®; PRENTOX®; SD 1750®; SUCHLOR®; SZKLARNIAK®; TAP 9VP®; TASK®; TENAC®; TETRAVOS®; UNIFOS (PESTICIDE)®; UNITOX®; VAPONA® et al. [C]; VAPONITE®; VERDICAN®; VERDIPOR®; VERDISOL®; VINYLOFOS®; VINYLOPHOS®; WINYLOPHOS®

Contact allergens

Cases of sensitization to this organophosphorus compound with several commercial names (Benfos, Brevinyl, Chlorvinphos, DDVP, Equigard, Fly fghte, Nogos, and Unifos) were occupationally seen in chry- santhem growers, horticulturists, technicians, and in a chemist.

Safety Profile

Confirmed carcinogen with carcinogenic and tumorigenic data. Poison by ingestion, inhalation, skin contact, subcutaneous, intravenous, and intraperitoneal routes. Experimental teratogenic and reproductive effects. Human mutation data reported. A cholinesterase inhibitor, it is used in flea (pest) collars for pets. No neurotoxicity has been observed. It is very rapidly metabolized and excreted. When heated to decomposition it emits very toxic fumes of Cl and POx. See also PARATHION.

Potential Exposure

A potential danger to those involved in manufacture, formulation and application of this fumigant insecticide in household, public health and agricultural uses. Used as an insecticide and as an anthelminthic for swine and dogs.

Veterinary Drugs and Treatments

Dichlorvos is effective in swine against Ascaris, Trichuris, Ascarops strongylina and Oesophagostomum spp.
Dichlorvos as a “No Pest Strip” is used as an ectoparasiticide for small mammals. It is also used as a premise spray to keep fly populations controlled.
In horses, dichlorvos is labeled as being effective for the treatment and control of bots, pinworms, large and small bloodworms, and large roundworms, but no systemic equine products are currently being marketed in the USA.
Dichlorvos was available for use internally in dogs and cats for the treatment of roundworms and hookworms, but no products are currently being marketed since newer, safer and more effective anthelmintics have replaced dichlorvos.

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. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Speed in removing material from skinis of extreme importance. Shampoo hair promptly if contaminated. Seek medical attention immediately. If thischemical has been inhaled, remove from exposure, beginrescue breathing (using universal precautions, includingresuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Medical observation is recommended for 24-48 h following overexposure.

Carcinogenicity

Two epidemiological studies reporting an association between exposure to dichlorvos resin strips and childhood cancer were reviewed by EPA and found to have biases and confounders that could explain the observed associations. Additional studies that correct for the control of potential biases and problems of exposure determination are needed before an association between dichlorvos and childhood cancer can be established.

Environmental Fate

Biological. When dichlorvos was incubated with sewage sludge for one week at 29°C, it was converted to dichloroethanol, dichloroacetic acid, ethyl dichloroacetate and an inorganic phosphate. In addition, dimethyl phosphate formed in the presence or absence of microorganisms (Lieberman and Alexander, 1983). Dichlorvos 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 one day of incubation, the percent of dichlorvos degradation that occurred in autoclaved, irradiated and nonsterile soils were 17, 88 and 99, respectively (Getzin and Rosefield, 1968).
Soil. In a silt loam and sandy loam, reported Rf values were 0.79 and 0.80, respectively (Sharma et al., 1986).
Plant. Metabolites identified in cotton leaves include dimethyl phosphate, phosphoric acid, methyl phosphate and O-demethyl dichlorvos (Bull and Ridgway, 1969).
Photolytic. Dichlorvos should not undergo direct photolysis since it does not absorb UV light at wavelengths >240 nm (Gore et al., 1971).
Chemical/Physical. Releases very toxic fumes of phosphorus oxides and chlorine when heated to decomposition (Sax and Lewis, 1987).
Slowly hydrolyzes in water and in acidic media but is more rapidly hydrolyzed under alkaline conditions to dimethyl hydrogen phosphate and dichloroacetaldehyde (Capel et al., 1988; Hartley and Kidd, 1987; Worthing and Hance, 1991). In the Rhine River (pH 7.4), the hydrolysis half-life of dichlorvos was 6 hours (Capel et al., 1988).
Atkinson and Carter (1984) estimated a half-life of 320 days for the reaction of dichlorvos with ozone in the atmosphere.

Metabolic pathway

The metabolism of dichlorvos has been extensively studied particularly in mammals. Dichlorvos is rapidly transformed in both environmental and biological situations via a hydrolytic mechanism to yield dimethyl phosphate and dichloroacetaldehyde which is further metabolised to 2,2-dichloroethanol or dechlorinated to glycolic acid. An additional important route in mammals involves demethylation catalysed by glutathione-S-methyl transferase to yield methylglutathione and desmethyldichlorvos.

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with dichlorvos you should be trained on its proper handling and storage. Store in tightly closed containers in a cool, wellventilated area away from strong acids; strong alkalis.Dichlorvos will attack some forms of mild iron, plastics,rubber, and coatings.

Shipping

UN3018 Organophosphorus pesticides, liquid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials

Degradation

Dichlorvos is slowly hydrolysed in water and in acidic media and rapidly hydrolysed by alkali to dichloroacetaldehyde (2) and dimethyl phosphate (3) (PM)

Toxicity evaluation

Acute oral LD₅₀ for rats: ca. 50 mg /kg

Incompatibilities

Contact with oxidizers may cause the release of phosphorous oxides. Organophosphates are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrideds and active metals. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides Corrosive to iron, mild steel, some forms of plastics, rubber, and coatings

Waste Disposal

50% hydrolysis is obtained in pure water in 25 minutes @ 70_x0003_°C and in 61.5 days @ 20C. A buffered solution yields 50% hydrolysis (37.5°C) in 301 minutes at pH 8, 462 minutes at pH 7, 620 minutes at pH 5.4. Hydrolysis yields no toxic residues. Incineration in a furnace equipped with an afterburner and alkaline scrubber is recommended as is alkaline hydrolysis followed by soil burial. 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.