Chemical Properties
Colorless to Pale Yellow Oil
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.
Uses
Cholinesterase inhibitor. Anthelmintic, insecticide.
Definition
ChEBI: An alkenyl phosphate that is the 2,2-dichloroethenyl ester of dimethyl phosphate.
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.
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.
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.
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.
First aid
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.
Medical observation is recommended for 24 to 48 hours
following overexposure
Shipping
UN3018 Organophosphorus pesticides, liquid,
toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials
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.
Physical properties
Colorless to yellow liquid with a mild aromatic odor
Production Methods
Dichlorvos is commercially produced through a multi-step synthesis that centres on the formation of its dimethyl phosphate ester structure. The process typically begins with the reaction of dimethyl phosphite with 2,2-dichlorovinyl alcohol or its derivatives, under controlled conditions that promote esterification. This reaction is carried out in the presence of a catalyst and an organic solvent, with temperature and pH carefully regulated to ensure high yield and purity.
Brand name
Atgard (Boehringer Ingelheim Animal Health); Equigard (Boehringer Ingelheim Animal Health); Equigel (Boehringer Ingelheim Animal Health); TASK Tabs (Boehringer Ingelheim Animal Health).
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®
Mechanism of action
Respiratory, contact and stomach action. Acetylcholinesterase (AchE) inhibitor.
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.
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.
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
Toxics Screening Level
The initial threshold screening level (ITSL) for dichlorvos is 0.5 μg/m3 with an annual averaging time (AT).
Pesticide Type
Insecticide; Acaricide; Metabolite
