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<br />htlp: htce.orst.edu/cgi-bin/mfsioI/pips/paraquat.hun
<br />caused skin sensitization in guinea pigs in some formulations [87]. Effects due to high acute
<br />exposure to paraquat may include excitability and lung congestion, which in some cases leads to
<br />convulsions, incoordination, and death by respiratory failure [87]. If swallowed, burning of the
<br />mouth and throat often occurs, followed by gastrointestinal tract irritation, resulting in abdominal
<br />pain, loss of appetite, nausea, vomiting, and diarrhea [8]. Other toxic effects include thirst,
<br />shortness of breath, rapid heart rate, kidney failure, lung sores, and liver injury [32]. Some
<br />symptoms may not occur until days after exposure. Persons with lung problems may be at increased
<br />risk from exposure. Many cases of illness and/or death have been reported in humans. The
<br />estimated lethal dose (via ingestion) for paraquat in humans is 35 mg/kg [8]. A maximum of 3.5
<br />mg/hour could be absorbed through the dermal or respiratory route without damage [32].
<br />• Chronic toxicity: As indicated above, repeated exposures may cause skin irritation, sensitization,
<br />or ulcerations on contact [58,87]. In animal studies, rats showed no effects after being exposed for
<br />years to paraquat at doses of 1.25 mg/kg/day [8]. Dogs, however, developed lung problems after
<br />being exposed for 2 years at high doses (above 34 mg/kg/day) [8]. In a study of 30 workers spraying
<br />paraquat over a 12 -week period, approximately one-half had minor irritation of the eyes and nose
<br />[8]. Of 296 spray operators with gross and prolonged skin exposure, 55 had damaged fingernails as
<br />indicated by discoloration, nail deformities, or loss of nails [8].
<br />• Reproductive effects: In a long-term rat study at doses up to 5 mg/kg/day, no adverse reproductive
<br />effects were reported [I I I ]. However, paraquat dichloride injected intraperitoneally at 3 mg/kg/day
<br />on days 8 to 16 of gestation increased fetal mortality in rats [8]. Hens given high levels of paraquat
<br />in their drinking water for 14 days produced an increased percentage of abnormal eggs [8]. It is
<br />unlikely to cause reproductive effects in humans at expected exposure levels.
<br />• Teratogenic effects: Offspring of mice dosed with high doses of paraquat during the
<br />organ -forming period of pregnancy had less complete bone development than the mice given lower
<br />doses [ 111 ]. Offspring of rats given similar treatment showed no developmental defects at any
<br />dose, but fetal and maternal body weights were lower than normal [I I I ]. Other studies of paraquat
<br />using rabbits and mice have shown no teratogenic effects [8]. The weight of evidence suggests that
<br />paraquat does not cause birth defects at doses which might reasonably be encountered.
<br />• Mutagenic effects: Paraquat has been shown to be mutagenic in microorganism tests and mouse
<br />cell assays [8]. It was unclear what levels of exposure are necessary to produce these effects.
<br />• Carcinogenic effects: Mice fed paraquat dichloride for 99 weeks at high levels did not show
<br />cancerous growths [ 112]. Rats fed high doses for 113 (male) or 124 weeks (female) developed lung,
<br />thyroid, skin, and adrenal tumors [111]. Thus, the evidence regarding carcinogenic effects of
<br />paraquat is inconclusive.
<br />• Organ toxicity: Paraquat affects the lungs, heart, liver, kidneys, cornea, adrenal glands, skin, and
<br />digestive system.
<br />• Fate in humans and animals: Paraquat is not readily absorbed from the stomach, and is even more
<br />slowly absorbed across the skin. Oral doses of paraquat in rats are excreted mainly in the feces,
<br />while paraquat injected into the abdomen leaves through urine [8]. In the stomach and
<br />gastrointestinal tract, paraquat metabolites may be more readily absorbed than the parent
<br />compound, but their identities and toxicities are unknown [I I I ]. Paraquat may concentrate in lung
<br />tissue, where it can be transformed to highly reactive and potentially toxic forms [87]. In one study,
<br />farm animals excreted over 90% of the administered paraquat within a few days. It was slightly
<br />absorbed and metabolized in the gastrointestinal tract. Milk and eggs contained small amounts of
<br />two paraquat metabolites [58].
<br />Ecoloqical Effects:
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