|
:XTOXNET PIP -DIMETHOATE Page 2 of
<br /> but for the technical grade is only 350 to 400 mg/kg [2]. It is not clear whether the increased toxicity results from
<br /> impurities present initially in the technical product or whether these may be formed from degradation over time [2
<br /> Reported dermal LD50 values for dimethoate are 100 to 600 mg/kg in rats, again with a much lower value for an
<br /> earlier product [2,13]. Dimethoate is reportedly not irritating to the skin and eyes of lab animals [8,13]. Severe eye
<br /> irritation has occurred in workers manufacturing dimethoate, although this may be due to impurities [2]. Via the
<br /> inhalation route, the reported 4-hour LC50 is greater than 2.0 mg/L, indicating slight toxicity [13]. Effects of acute
<br /> exposure are those typical of organophosphates. Symptoms of acute exposure to organophosphate or cholinesteras
<br /> inhibiting compounds may include the following: numbness, tingling sensations, incoordination, headache,
<br /> dizziness, tremor, nausea, abdominal cramps, sweating,blurred vision, difficulty breathing or respiratory
<br /> depression, and slow heartbeat. Very high doses may result in unconsciousness, incontinence, and convulsions or
<br /> fatality. Persons with respiratory ailments, recent exposure to cholinesterase inhibitors, impaired cholinesterase
<br /> production, or liver malfunction may be at increased risk from exposure to dimethoate. High environmental
<br /> temperatures or exposure of dimethoate to visible or UV light may enhance its toxicity [2].
<br /> . Chronic toxicity: There was no cholinesterase inhibition in an adult human who ingested 18 mg(about 0.26
<br /> mg/kg/day) of dimethoate/day for 21 days. No toxic effects and no cholinesterase inhibition were observed in
<br /> individuals who ingested 2.5 mg/day (about 0.04 mg/kg/day) for 4 weeks. In another study with humans given ora
<br /> doses of 5, 15, 30, 45 or 60 mg/day for 57 days, cholinesterase inhibition was observed only in the 30 mg/day and
<br /> higher dosage groups [2]. Repeated or prolonged exposure to organophosphates may result in the same effects as
<br /> acute exposure, including the delayed symptoms. Other effects reported in workers repeatedly exposed include
<br /> impaired memory and concentration, disorientation, severe depression, irritability, confusion, headache, speech
<br /> difficulties, delayed reaction times,nightmares, sleepwalking, and drowsiness or insomnia. An influenza-like
<br /> condition with headache, nausea, weakness, loss of appetite, and malaise has also been reported [2].
<br /> . Reproductive effects: When mice were given 9.5 to 10.5 mg/kg/day dimethoate in their drinking water, there wa.,
<br /> decreased reproduction, pup survival, and growth rates of surviving pups. Adults in this study exhibited reduced
<br /> weight gain, but their survival was not affected. In a three-generation study with mice, 2.5 mg/kg/day did not
<br /> decrease reproductive performance or pup survival [2]. Once in the bloodstream, dimethoate may cross the placen
<br /> [2]. Impaired reproductive function in humans is not likely under normal conditions.
<br /> . Teratogenic effects: Dimethoate is teratogenic in cats and rats [8,2]. A dosage of 12 mg/kg/day given to pregnant
<br /> cats increased the incidence of extra toes on kittens [2,8]. The same dosage given to pregnant rats produced birth
<br /> defects related to bone formation, runting and malfunction of the bladder. Dosages of 3 or 6 mg/kg/day were not
<br /> teratogenic in cats or rats [2]. No effects were observed in cats and rats at doses of 2.8 mg/kg/day. There were no
<br /> teratogenic effects seen in the offspring of mice given 9.5 to 10.5 mg/kg/day dimethoate in their drinking water [2
<br /> It is not likely that teratogenic effects will be seen in humans under normal circumstances.
<br /> . Mutagenic effects: Mutagenic effects due to dimethoate exposure were seen in mice. They were more prominent
<br /> male mice given a single high dose of dimethoate than in male mice given one twelfth of the same dose daily for
<br /> days [2]. Mutagenic effects are unlikely in humans under normal circumstances.
<br /> . Carcinogenic effects: An increase in malignant tumors was reported in rats given oral doses of 5, 15 or 30
<br /> mg/kg/day dimethoate for over a year. The increases were not, however, dose dependent [2]. That is, higher doses
<br /> did not necessarily result in higher tumor rates. Thus the evidence of carcinogenicity, even with high-dose, long-
<br /> term exposure, is inconclusive. This suggests carcinogenic effects in humans are unlikely.
<br /> . Organ toxicity: Target organs as determined through animal tests include the testicles, kidneys, liver, and spleen
<br /> [2]•
<br /> . Fate in humans and animals: Dimethoate is rapidly metabolized by mammals. Rats excreted about 50 to 60%of
<br /> administered doses in urine, expired air and feces within 24 hours [2]. Human volunteers excreted 76 to 100% of
<br /> administered dimethoate within 24 hours [2]. The rate of metabolism and elimination varied in several species
<br /> tested. Amongst several mammalian species tested, dimethoate appears to be less toxic to those animals with high
<br /> liver-to-body weight ratios and to those with the highest rate of dimethoate metabolism [2]. Following application
<br /> of dimethoate to the backs of cows at 30 mg/kg, the concentration of dimethoate reached a maximum level of 0.0:
<br /> ppm in blood and milk in about 3 hours, and decreased to 0.01 ppm within 9 hours [2].
<br /> ittp://extoxnet.orst.edu/pips/dimethoa.htm 6/25/20
<br />
|