Chemical Properties
Phosphamidon is a pale yellow to colorless oily liquid with a faint odor. It is miscible
with water and is soluble in aromatic hydrocarbons. Phosphamidon decomposes on
heating and releases highly toxic fumes, such as phosphorus oxides, hydrogen chloride,
and nitrogen oxides. It reacts with bases (hydrolysis) and attacks metals such as iron,
tin, and aluminium. Phosphamidon should be handled by trained personnel wearing
protective clothing. Phosphamidon is used as a broad-spectrum insecticide and acaricide
for the control of pests and vectors on crops like sugar cane, rice, citrus orchards,
and cotton. Occupational exposures to phosphamidon occur among factory workers
involved in synthesizing formulation and dispensing spray operations. Human exposures
also occur among crop harvesters and in vector control operations.
General Description
Pale yellow oily liquid with a faint odor. Used as an insecticide for citrus, cotton, and deciduous fruit and nuts. and as an acaricide.
Air & Water Reactions
Water soluble. Hydrolyzed by alkali with a half-life at 73°F of 13.8 days at pH 7 and 2.2 days at pH 10 .
Reactivity Profile
PHOSPHAMIDON is corrosive to iron, tin and aluminum. Incompatible with alkaline preparations and should not be mixed with copper oxychloride, captan, folpet or sulfur.
Health Hazard
PHOSPHAMIDON is extremely toxic; the probable oral lethal dose for humans is 5-50 mg/kg, or between 7 drops and 1 teaspoonful for a 150-lb person. It is a cholinesterase inhibitor.
Fire Hazard
(Non-Specific -Organophosphorus Pesticide, Liquid, n.o.s.) Container may explode in heat of fire. Heat above 320F may cause decomposition and evolution of highly toxic fumes of phosphorus oxides and chlorides. Hydrolyzes in alkali. Stable in neutral and acid media. Hydrolyzes in alkali.
Health Hazard
Phosphamidon is readily absorbed from the gastrointestinal tract, through the intact skin,
and by inhalation of spray mists and dusts. Prolonged exposures to phosphamidon cause
adverse effects and impairment on the respiratory, myocardial, and neuromuscular transmission
in animals and humans. Phosphamidon does not cause delayed peripheral neuropathy
in hens. The symptoms of poisoning include, but are not limited to, nausea, vomiting,
diarrhea, abdominal cramps, headache, dizziness, eye pain, blurred vision, constriction or
dilation of the pupils, tears, salivation, sweating, and confusion. Prolonged period of exposures
to phosphamidon cause incoordination, slurred speech, loss of refl exes, weakness,
fatigue, involuntary muscle contractions, twitching, tremors of the tongue or eyelids, and
eventually paralysis of the body extremities and the respiratory muscles, involuntary defecation
or urination, psychosis, irregular heart beat, unconsciousness, convulsions, coma,
respiratory failure or cardiac arrest leading to death. Phosphamidon has caused clastogenic
effects in the bone marrow cells of rats and mice. However, the studies are found
to be inadequate to arrive at meaningful conclusions about phosphamidon as a human
carcinogen and no data are available. The ADI for phosphamidon has been reported as
0.0005 mg/kg body weight. (ADI: acceptable daily intake is an estimate of the amount of
a pesticide, expressed on a body weight basis, which can be ingested daily over a lifetime
without appreciable health risk.)
Potential Exposure
This material is used as an insecticide on citrus, cotton, and deciduous fruit and nuts. It is also an acaricide.
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. Obtain autorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures. Transport to a health care facility. Medical observation is recommended for 2448 hours after breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema,a doctor or authorized paramedic may consider administeringa drug or other inhalation therapy.
Shipping
UN3018 Organophosphorus pesticides, liquid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.
Incompatibilities
Compounds of the carboxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water and a salt that may be harmful. Incompatible with arsenic compounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, and sulfides (releasing heat, toxic and possibly flammable gases), thiosulfates and dithionites (releasing hydrogen sulfate and oxides of sulfur). Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Strong oxidizers may cause release of toxic phosphorus oxides. Organophosphates, in the presence of strong reducing agents such as hydrides, may form highly toxic and flammable phosphine gas. Keep away from alkaline materials. Attacks metals, such as aluminum, iron, tin.
Waste Disposal
Small quantities may be treated with alkali followed by landfill disposal. Large quantities should be incinerated with effluent gas scrubbing. 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.
Uses
Insecticide used to control sap-feeding insects and other pests in a wide variety of
crops
Uses
Phosphamidon is used to control sucking and boring insects and
mites in a very wide range of crops and in forestry applications.
Definition
ChEBI: Phosphamidon is a trialkyl phosphate, an organophosphate insecticide, an organochlorine insecticide and an organophosphate nematicide. It has a role as an EC 3.1.1.7 (acetylcholinesterase) inhibitor, an EC 3.1.1.8 (cholinesterase) inhibitor, an acaricide and an agrochemical. It is functionally related to a N,N-diethyl-3-hydroxybut-2-enamide.
Environmental Fate
Chemical/Physical. Emits toxic fumes of chlorine, phosphorus and nitrogen oxides
when heated to decomposition (Sax and Lewis, 1987)
Metabolic pathway
The metabolism of phosphamidon has been reviewed by Geissbuhler et al.
(1971) and Beynon et al. (1973). Technical phosphamidon consists of two
stereochemical isomers in the E:Z ratio of ca. 3:7. The Z-isomer has the
greater insecticidal activity. It is important to note that in the case of
phosphamidon the isomer with the phosphate ester function trans to
the amide group is assigned the Z configuration due to the priority of
chlorine, whereas in the case of mevinphos, monocrotophos and dicrotophos
it is assigned the E configuration. In all four compounds, the isomers
with this configuration (also referred to as the cis-crotonamide or crotonate
structure) have the greater insecticidal activities. It is a systemic
insecticide which is rapidly translocated in the plant via the xylem. Phosphamidon
is rapidly degraded in the environment, the major routes being
via N-de-ethylation and cleavage of the P-O-vinyl function. The resultant
N,N-diethyl-2-chloroacetoacetamide or N-ethyl-2-chloroacetoacetamide
are then degraded via dechlorination and hydrolysis, ultimately to give
acetone, diethylamine and ethylamine. Conjugated metabolites have not
been identified.
Metabolism
The major routes of degradation are oxidative
dealkylation of the amide group and hydrolysis of the vinyl
phosphate ester bond. Dechlorination also occurs. In soils,
DT50 is 7–25 d depending upon the soil type.
Degradation
Phosphamidon is rapidly hydrolysed by alkali (PM) but it is relatively
stable at neutral and acidic pH values. In alkaline solution, the compound
is hydrolysed to N,N-diethyl-2-chloroacetoacetamide (2) and
dimethyl phosphate (3) (Anliker and Beringer, 1971). There was apparently
no attack on the P-O-Me bond to give the desmethyl compound. In
acidic solution compound 2 was hydrolysed to give chloroacetone (4),
diethylamine (5) and C02. In alkaline solution 2 was dechlorinated and
hydrolysed to acetone (6), acetic acid (7) and glycolic acid diethylamide
(8). These pathways are shown in Scheme 1.
Toxicity evaluation
The
acute oral LD50 for rats is 17.9–30 mg/kg. Inhalation LC50
(4 h) for rats is about 0.18 mg/L air. NOEL (2 yr) for rats is
1.25 mg/kg b.w. daily. ADI is 0.5 μg/kg b.w. Phosphamidon
administered in animals is rapidly metabolized, and
85–90% of the dose is excreted within 24 h almost all in
the urine.
