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adaptive management

There were sufficient toxicological data to derive LOAELs to fulfill the minimum requirements for derivation of the SQGI (Tables 6 and 7). The protocol (CCME 2005) requires a minimum of two mammalian oral studies (one of which should include a grazing herbivore such as an ungulate) and one avian oral study. The database for avian species indicated a minimum NOAEL of 16 mg/kg bw/d for adverse effects in American black duck (Haseltine and Sileo 1983; Sample et al. 1996). Although single dose injection studies established lower LOAELs for Japanese quail (Kupsh et al. 1991) and Leghorn chickens (Harvey et al. 1986), this route of administration and the length of exposure were not considered relevant in the derivation of an environmental guideline. For mammalian livestock, only one study on dairy cattle was available (fulfilling the requirement for a grazing ungulate). In this study, a LOAEL of 0.62 mg/kg bw/d was determined for effects on general health and milk yield of cows (Garner 1963). All other oral toxicity data available for mammals were for laboratory animals such as mice, rats, rabbits and dogs (Table 7). The lowest LOAELs reported were 0.06 and 0.09 mg/kg bw/d for renal effects in male and female laboratory rats, respectively, that were administered uranyl nitrate in drinking water over a 91-day period (Gilman et al. 1998c). The next lowest acceptable LOAEL was 0.49 mg/kg bw/d for renal effects in female New Zealand white rabbits that were also administered uranyl nitrate in drinking water over a 91-day period (Gilman et al. 1998a). A lower LOAEL of 0.05 mg/kg bw/d was reported in the same study for renal effects in male rabbits (Gilman et al. 1998a). This endpoint, however, was considered suspect due to the potential confounding factor of a bacterial (Pasturella multocida) infection that was noted in several of the male rabbits.