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EXTOXNET PIP-ORYZALIN http://extoxnet.orst.edu/pips/oryzalin.htm Repeated ingestion of large doses led to adverse changes in blood cell formation in dogs [8]. Mice given dietary doses of about 200 mg/kg/day for 1 year exhibited decreased uterine and ovarian weights. Those exposed to doses of 75 mg/kg/day showed no observable effects [107]. • Reproductive effects: There were no adverse effects on reproduction in a three-generation study of rats fed dietary concentrations of 12.5, 37.5, or 112.5 mg/kg/day, the highest dose tested. Fetotoxic effects appeared at 12.5 mg/kg/day[58,107]. It does not appear that oryzalin causes reproductive effects. • Teratogenic effects: There were no birth defects in the offspring of pregnant rats fed dietary concentrations as high as 112 mg/kg/day for three generations, nor in the offspring of pregnant rabbits given doses of 125 mg/kg/day, the highest dose tested [8,107]. It appears that oryzalin is unlikely to cause teratogenic effects. • Mutagenic effects: Oryzalin was not mutagenic in several tests, including tests on live rats and mice and on bacterial cell cultures [107]. It does not appear that oryzalin is mutagenic. • Carcinogenic effects: When oryzalin was fed to rats in doses as high as 135 mg/kg/day for 2 years, there was an increase in the incidence of thyroid, mammary, and skin tumors [107]. Thyroid tumors and benign skin and mammary tumors occurred in rats fed a dietary level of 45 mg/kg/day for 2 years [107]. However, there were no tumors in mice fed doses as high as 548 mg/kg/day for 2 years [107]. Because of these conflicting results, it is not possible to assess the carcinogenicity of oryzalin. • Organ toxicity: Oryzalin has shown systemic effects on the thyroid, liver, and kidneys, as well as blood chemistry, in animal tests. • Fate in humans and animals: Oryzalin is moderately well-absorbed from the gastrointestinal tract, and rapidly metabolized and eliminated following absorption. When oryzalin was administered to male rats, 40% of the dose was excreted in the urine and 40% in the feces within 3 days. Similar results were obtained in tests with rabbits, a steer, and with Rhesus monkeys [106]. Ecological Effects: • Effects on birds: Oryzalin is slightly toxic to practically non-toxic to birds; the reported oral LD50 values in bobwhite quail and mallard ducks are greater than 500 mg/kg, and in chickens is 1000 mg/kg [1,58]. The 5-day dietary LC50 values in quail and mallard ducks are greater than 5000 ppm [8]. • Effects on aquatic organisms: Oryzalin is highly toxic to fish, with reported 96-hour LC50 values of 2.88 mg/L in bluegill sunfish, 3.26 mg/L in rainbow trout, and greater than 1.4 mg/L in goldfish fingerlings [8]. • Effects on other organisms: The reported oral LD50 for the compound in bees is 11 ug/bee, indicating it is nontoxic to bees [1,58]. Environmental Fate: • Breakdown in soil and groundwater: Oryzalin is of low to moderate persistence in the field, with reported field half-lives ranging from 20 to 128 days [58,11]. A representative value for soil half-life is estimated to be 20 days [11,58]. Microbial degradation is mainly responsible for the breakdown of oryzalin in soils, but it may undergo photodecomposition near the soil surface [58]. Volatilization is not appreciable [58]. Oryzalin is slightly soluble in water and it does not have a strong tendency to adsorb to soil particles [58,11]. It is bound to a greater extent with increasing soil organic matter and clay content. In soils with low proportions of these, high water tables and increased rainfall, oryzlin may be mobile, and thus present a risk of contamination to groundwater. 2 of 4 2/20/2008 2:07 PM