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EXTOXNET 111€'- €'ARAQUATr"%I ttp://ace.orst.edu/cgi-bin/mi's/01/pips/paraquat.hini
<br /> exposure to paraquat may include excitability and lung congestion, which in some cases leads to
<br /> I convulsions, incoordination, and death by respiratory failure [87]. If swallowed, burning of the
<br /> a' 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 /> G 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 2
<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 [111]. 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 organ-forming
<br /> period of pregnancy had less complete bone development than the mice given lower doses [1111.
<br /> Offspring of rats given similar treatment showed no developmental defects at any dose, but fetal and
<br /> maternal body weights were lower than normal [111]. Other studies of paraquat using rabbits and
<br /> mice have shown no teratogenic effects [8]. The weight of evidence suggests that paraquat does not
<br /> 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 /> k cell assays [8]. It was unclear what levels of exposure are necessary to produce these effects. l
<br /> • Carcinogenic effects: Mice fed paraquat dichloride.for 99 weeks at high levels did not show
<br /> cancerous growths [1121. Rats fed high doses for 113 (male) or 124 weeks (female) developed lung,
<br /> thyroid, skin, and adrenal tumors [1I]. 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 i
<br /> gastrointestinal tract, paraquat metabolites may be more readily absorbed than the parent compound,
<br /> but their identities and toxicities are unknown I i 1]. Paraquat may concentrate in lung tissue, where
<br /> it can be transformed to highly reactive and potentially toxic forms [87]. In one study, farm animals
<br /> k excreted over 90% of the administered paraquat within a few days. It was slightly absorbed and
<br /> metabolized in the gastrointestinal tract. Milk and eggs contained small amounts of two paraquat
<br /> metabolites [58].
<br /> � E
<br /> Ecological Effects:
<br /> • Effects on birds: The compound is moderately toxic to birds, with reported acute oral LD50 values
<br /> of 981 mg/kg and 970 mg/kg in bobwhite and Japanese quail, respectively [58]. The reported 5- to
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