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EXTOXNET PIP - ORYZALIN Pagel of 3 EXTOXNET Extension Toxicology Network Pesticide Information Profiles A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University,the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program. EXTOXNET primary files maintained and archived at Oregon State University Revised June 1996 Oryzalin Trade and Other Names:Trade names include Dirimal, EL-119,Rycelan, Ryzelan, Ryzelon, and Surflan. Regulatory Status: Oryzalin is a slightly to practically nontoxic compound in EPA toxicity class IV. Products containing oryzalin must bear the Signal Word CAUTION. It is a General Use Pesticide(GUP). Chemical Class: Not Available Introduction: Oryzalin is a selective pre-emergence surface-applied herbicide used for control of annual grasses and broadleaf weeds in fruit trees, nut trees, vineyards, established bermuda grass turf, and established ornamentals. It inhibits the growth of germinating weed seeds by blocking cell division in the meristems. It is available in aqueous suspension, dry flowable, and wettable powder formulations. Formulation: It is available in aqueous suspension, dry flowable, and wettable powder formulations. Toxicological Effects: . Acute toxicity: Oryzalin is practically nontoxic by ingestion, with reported oral LD50 values of greater than 5000 mg/kg in rats and mice [1,58], and greater than 1000 mg/kg in cats, dogs, and chickens [1,106]. The dermal LD50 for technical oryzalin in rabbits is greater than 2000 mg/kg, indicating slight to practically no toxicity by this route [58]. It is reported to cause slight skin and eye irritation in the rabbit, and no skin sensitization in the guinea pig [58]. It is also slightly toxic when inhaled, with a 4-hour inhalation LC50 of greater than 3 mg/L in rats [58]. The formulated products (e.g., Surflan A.S.) may show moderate toxicity by either the oral or inhalation routes, and may show skin and eye irritation and skin sensitization properties [58]. In dogs and cats, large oral doses cause nausea and vomiting [8]. . Chronic toxicity: Rats fed a dietary level of about 2.5 mg/kg/day for 2 years exhibited blood changes, increased liver and kidney weights, inhibition of growth, and decreased survival [8]. 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 http://extoxnet.orst.edu/pips/oryzalin.htm 3/26/2007