Toxicological Effects of Acephate

Acute Toxicity: The amount of acephate that is lethal to one-half (50%) of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The acute oral toxicity of acephate to mammals is medium (LD50 = 500-5,000 mg/kg) to high (LD50 = 50-500 mg/kg), and acute toxicity from inhalation is medium (LC50 = 2-20 mg/l) (115). The acute dermal LD50 for rabbits is 2,000 mg/kg; no irritation or sensitization was observed in skin tests on guinea-pigs. The effect of 900 mg/kg on cholinesterase inhibition in rats was not as severe as parathion at 15 mg/kg. Atropine sulfate is an effective antidote. The acute oral LD50 for technical grade acephate in female rats is 866 mg/kg; 945 mg/kg for male rats; 361 mg/kg for mice; 350 mg/kg for mallard ducks; 852 mg/kg for chickens; and 140 mg/kg for ringneck pheasants. The oral LDLo (Lethal Dose Low - lowest dose of a substance other than LD50 introduced by any route other than inhalation, over any given period of time in one or more divided portions and reported to have caused death in humans or animals) for dogs is 681 mg/kg. The lethal concentration fifty, or LC50, is that concentration of a chemical in air or water that kills half of the experimental animals exposed to it for a set period of time. The 96 hour LC50 for rainbow trout is >1,000 mg/l; 2,050 mg/l for bluegill fish; 1,725 mg/l for largemouth black bass; 2,230 mg/l for channel catfish; and 9550 mg/l for goldfish. The toxicity of acephate to rainbow trout increased with increasing temperature.

Chronic Toxicity: In 2-year feeding trials, dogs exhibited depression of cholinesterase at 100 mg/kg diet (maximum dose level) of acephate but no other significant effects; rats showed depression of cholinesterase but no effect on weight gain or pathological effect at 30 mg/kg diet. Another feeding study noted that rats did not produce pathological changes over a 90-day period when fed up to 300 mg/kg body weight of acephate. Acephate has a negligible chronic toxicity to fish.

• Reproductive Effects: Acephate is considered a fetotoxin (can poison the fetus) and there is some evidence of hormonal effects.
• Teratogenic Effects: No effects were observed in 2-year feeding trials on dogs.
• Mutagenic Effects: No effects were observed in 2-year feeding trials on dogs.
• Carcinogenic Effects: No effects were observed in 2-year feeding trials in dogs.
• Organ Toxicity: Exposure effects of acephate in humans can include: cardiac responses (bradycardia/tachycardia, heart block), central nervous system impairment, eye problems (miosis/mydriasis, loss of accommodation, ocular pain, sensation of retrobulbar pressure, tearing, dark or blurred vision, conjunctiva hyperemia, cataracts), gastrointestinal problems (abdominal cramps, heart burn, hyperperistalsis), respiratory effects (apnea, dyspnea, hypopnea, atelectasis, bronchoconstriction, bronchopharyngeal secretion, chest tightness, productive cough, rales/ronchi, wheezing, pulmonary edema, laryngeal spasms, rhinorrhea, oronasal frothing) and death due to respiratory failure.

Fate in Humans and Animals. Exposure to acephate can result in alkyl phophates in urine.