9543 - Laserfiche WebLink

Home Browse Search

DcI'orcst, llrix, am! Adams Debate/Commentary and logit models were Iil to the larval mOrlalily (Abhott's coITecte<l) and growth data at 60 and 90 days (Figures 9 and 10). The lowest ECw, EC~lI' and ECsu values for mOrlality from cilher model are 19,27, and 4 I mg/kg <lw aftcr day 60 and 3.4, 5.3, and 12 mg/kg dw aher day 90. Based on thc growth endpoint, the lowcst ECw, EGlll, and EC5l, values from either model arc II, 17, and 30 mg/ kg dw aftcr day 60 and 10, 15, and 24 mg/ kg dw aher day 90. For the samc reasons discusscd above, fUrlhc," studies on chinook salmon should be conducted to verify thcse results, as well as studies of nonanadromous coldwater fish in order to determinc if they are similarly sensitive. For wannwater fish, similar to the ovary versus lalval mortality analyses described above. we <:ompared larval mortality data to dietary selellium con- centrations led to the parcnl/ish. The relev.lIlt studies IllI" this .Inalysis were Ogle and Knight ( 19M9), lll)'son el aI. (19M5b). Wom.:k el aI. (19M7). and Coyle el ai. (1993). Probit and logit models were fillO thc lalvalmorlality and <liclm)' selenium dala fl'Om lhese sludies. The model /ilS werc relatively poor, prima- rily duc to the exlrcme dillcrcnces in larval morlality in the Ogle and Knighl (19M9) and Woock el ai (1!1H7) sludies at a dielary conccnlralion of about 29 mg/kg dw. If thc Ogle and Knight (1989) fathead minnow dala are re- moved, the lilS of lhe probil and logit models become much beller (Figme 11). Larval mOrlalily may not have been as high in lhe Ogle and Knight (I !IM9) study because the falhead minnow diets were spiked with 50% selenilc, 25% selenale, and 25% organosclenium, and organoselcnium is more loxic Ihan inorganic selcnium (Woock el aI., J !>67). The ECw, EC~lI' a1l(1 ECslI values using the model excluding the Ogle and K.night (1989) dala are 10, 13, and 19 hased on bolh the probit and logilmodels. Using dala from all appropriale studies, we reconllnend lhe ECw of 10 mg/kg dw as the dietary threshold for huval mOrlality in wanmvaler lish. Similarly, Ihe ECw of II mg/kg dw is recom- mended as the diclary lhreshold lor reduced growth in lalval coldwaler anadromous /ish. The ECIII values from lhe prohit .\Ild logit models li)r h011l warmwater fish and coldwater anadromous suggest thallhe dietary guideline of 3 mg/kg dw recommended by l.emly (I 993a) may be overly collsclvativc. It must be reemphasizcd lhal the Hamillon el aI. (l990) study should he re- peated to delermine if lhe 90-day resulls arc illdeed villid and that lill'lher sludies should be conducled 10 examille the sensitivilies of chinook salmon relalivc to olher coldwaterlish (pal"licularly nonanadromous fish). Moreover, lhis threshold lor lalval coldwatcr anadromous /ish may he relevalll for mod- eling a lotie system, but probably nol a lenlic system. '\ '\.\ ... \ \" \ ".\ '",\ \ ". \. \. '...\ , l{ \, '\ ~ \ , ~ "1~:....: : : a! ri ~ ~j~:~ ;;; o 0 ~ UUU Iollollol ~ SUMMARy AND CONCLUSIONS The most appropriate lissue for developing a residue-based selcnium guide- line is the oval)'. 11 is the lJesl predictor of seleniulll conccnlralions to which embryos and larvae are exposed. Use of an oval)'-based guideline is also more appropriate than a dietal)'-bascd guideline because oval)' I'csidues represent the iUlegralion ofwalerlJorne and dietal)' exposures tllatnatnrallish popula- lions receive. Oue ofthe key uncel"lainties in establishing residue-based guide- o Q - Q 0\ Q 00 Q r-- Q \C Q III Q ..,. Q M (p;Jp;JJJO;) S,lJoqqv) ^JIIB)JOVt( IBUB'] % 1111111. Ewl. Risk Assess, Vol. 5, No. Ii, I !l!J!) '"'" 'tl ,..... .. 1l ~ ~ oS 0 III .... I:l III ~ I:l (-0 ~ ~~ Q Q ~ Q 0\ 0\ \C ~ ~,~, ~ -=:l ~ -=:l -=:l .t! oJ' .t! oJ' .g .~ .g .~ ,t .::s ,t ...J I .. Q M Q .... Q III ..,. Q ..,. 0- O'! en ..... <I' 'tl c: 9 :":l ~ ::r: s 0 J::l r3 g .- c: 0 ~ ~ 'tl ~ ". .! 0 0 c: .. :E II) ~ u '& .5 = ~ .. ~ '0 ~ 0 e ] ~ ~ 'C:: v ] ;.. " .8 v '0 ~ .Q ~ III M <:> f'l III M <:> M III .... Q .... III <:> 1219