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8.C.e <br />evidence in studies with two species, rat and mouse. In a study using mice, <br />diquat was not carcinogenic. <br />A supplemental developmental toxicity study using rats resulted in <br />maternal toxicity and developmental toxicity only at the highest dose level. <br />Another more recent study using rats resulted in effects at high dose levels <br />including decreases in fetal and litter weights, kidney effects, and incomplete <br />development of certain bones. In a supplementary study using rabbits, <br />decreased body weight gain in the high dose group was the only maternal <br />toxicity observed. A recent study using rabbits resulted in developmental <br />effects only in the high dose group, including liver effects and poor <br />ossification. A study using mice resulted in developmental toxicity only in <br />the high dose group, including decreased fetal body weight and increased <br />skeletal alterations. <br />A reproductive toxicity study using rats resulted in effects at the highest <br />dose level including decreased numbers of live pups per litter and decreased <br />body weight gain. Diquat dibromide was negative in four mutagenicity <br />studies and positive in two other studies. Metabolism studies indicate that it is <br />poorly absorbed from the gastrointestinal tract and primarily excreted in <br />urine. An acute neurotoxicity study using rats resulted in symptoms that may <br />not be due to direct neurotoxicity. In a subchronic neurotoxicity study, toxic <br />signs observed only in the high dose <br />group included cataracts and decreased body weight gain and food utilization. <br />Dietary Exposure <br />People may be exposed to residues of diquat dibromide through the diet. <br />Tolerances or maximum residue limits have been established for a variety of <br />crop and animal commodities (please see 40 CFR 180.226 (a) and (b)). A <br />food additive tolerance is established for residues in potable water (40 CFR <br />185.2500 (a) and (b)). Food and feed additive tolerances also are established <br />for residues in processed potatoes (including potato chips) (40 CFR 185.2500 <br />(c)) and processed potato waste (40 CFR 186.2600). <br />The registrant has proposed revised tolerances for many commodities, <br />some at EPA's recommendation. A tolerance for sugarcane must be revoked <br />since this use is no longer registered. A tolerance for potable water also will <br />be revoked since it has been replaced with a Maximum Contaminant Level <br />Goal (MCLG) under the Safe Drinking Water Act. The U.S. tolerances for <br />eggs, poultry, meat, and offal may be raised to achieve harmonization with <br />Codex Maximum Residue Levels (MRLs). With these changes, diquat <br />dibromide tolerances are considered appropriate. <br />EPA has assessed the dietary risk posed by diquat dibromide <br />considering both published and proposed tolerances. The Anticipated Residue <br />Concentration (ARC) for the overall U.S. population and 22 subgroups <br />represents 31 % of the Reference Dose (RfD), or amount believed not to cause <br />adverse effects if consumed daily over a 70-year lifetime. The most highly <br />Attachment: EPA Facts (2109 : Dukes Root Control) <br />3 <br />Packet Pg. 57 <br />