Toxicity and EliminationPrimary Exposure and RiskPrimaryExposureandRiskCharacterizationPrimaryExposureandRiskCharacterizationPresentation to the SAPNovember 29, 2011Christine Hartless, Ph.D.ChristineHartless,Ph.D.Environmental Fate and Effects Division1Outline•Analysis approach flowchart•Avian and mammalian acute toxicity endpoints•Single-day primary exposure and risk estimation•Multiple-day primary exposure and risk estimationdayprimaryexposureandriskestimation•Quantity of bait consumed to reach LD50body burden•Primary exposure conclusions2Primary consumers•Animals that eat plants, seeds,fruits,etc.•Primary exposure occurs whenthese animals have an opportunityto consume rodenticide bait.toconsumerodenticidebait.3Dose-based methodology flow chartToxicity endpointsConcentrationHalf-life in primaryScaledtoxicityof a.i. in bait1d d ti idconsumerScaledtoxicityed o c yendpoints basedon body weights1-day rodenticideintake via allometricfood intake equationsDaily body-burden forsingle day incrementsSca ed o c yendpoints basedon body weightsBody burden after6 days bait intake1-day exposure RQsg bait consumed and days to reach LD6-day exposure RQs4gbaitconsumedanddaystoreachLD50Toxicity endpoint selection•Acute oral (single dose) for birds and mammals•Acute dietary (5-day exposure) for birds and mammals•Most anticoagulant studies were conducted over an extendedtime period (30 days observation after exposure)•Values for RQ calculations based on most sensitive ofcommonly tested species*:Bi dll d d k b b hit il•rds–mallardduckorbobwhite quail•Mammals – laboratory rat*other available data evaluated in characterizationotheravailabledataevaluatedincharacterization5Selected avian and mammaliantoxicity values for RQ calculationChemicalBirds MammalsLD50 LC50 LD50 LC50Brodifacoum 0.25 1.33 0.48 0.53Difethialone0 300 560 56NodataDifethialone...Warfarin 525 625 3.0 5.4Chlorophacinone 258 72 6.26 7.2Diphacinone 1630 906 1.9 4.2Bromethalin 4.6 210 2.2 No dataLD50= mga.i./kg-bw650g gLC50= mg a.i./kg-dietAvian acute dose LD50s (mg a.i./kg-bw)BrodifacoumDifethialoneWarfarinChlorophacinoneDiphacinoneBromethalin0.1 1 10 100 1000 100007Endpoint for RQ calculationsLD50(mg a.i./kg-bw)Avian acute dietary LC50s (mg a.i./kg-diet)BrodifacoumDifethialoneWarfarinChlorophacinoneDiphacinoneBromethalin0.1 1 10 100 1000 100008Endpoint for RQ calculationsLC50(mg a.i./kg-diet)Mammalian acute dose LD50s (mg a.i./kg-bw)BrodifacoumDifethialoneWarfarinChlorophacinoneDiphacinoneBromethalin0.1 1 10 100 1000 100009Endpoint for RQ calculationsLD50(mg a.i./kg-bw)Mammalian acute dietary LC50s(mg a.i./kg-diet)BrodifacoumDifethialoneWarfarinChlorophacinoneDiphacinoneBromethalin0.1 1 10 100 1000 1000010Endpoint for RQ calculationsLC50(mg a.i./kg-diet)Body Weight Scaling of Avian LD50s•Scaled to 20, 100, and 1000 g•Mineauet al.,1996 (default and chemical specific)•Mineauet al., 2001 (chemical specific)•Also evaluated unadjusted LD5011Photo credits: USFWSBody Weight Scaling of Mammalian LD50s•Scaled to15, 35, and 1000 g•Standard USEPA approach (USEPA 2011)StandardUSEPAapproach(USEPA2011)•Also evaluated unadjusted LD5012Photo credits: USFWSUnadjusted and adjusted avian LD50sChemical UnadjustedAdjusted for body weight20 g 100 g 1000 gBrodifacoum 0.25 0.65 0.44 0.25Difethialone 0.30 0.21 0.27 0.38Warfarin 525 273 347 490Chlorophacinone258182232328Diphacinone 1630 1163 1480 2091Bromethalin 4.6 3.27 4.16 5.88LD50= mga.i./kg-bw1350g gUnadjusted and adjusted mammalianLD50sChemical UnadjustedAdjusted for body weight15 g 35 g 1000 gBrodifacoum 0.48 0.96 0.78 0.34Difethialone 0.56 1.11 0.90 0.39Warfarin 3.0 5.7 4.6 2.0Chlorophacinone6 2611 69 44 1....Diphacinone 1.9 4.8 3.9 1.7Bromethalin 2.2 3.7 3.0 1.3LD50= mga.i./kg-bw1450g gToxicity value uncertainties•Missing endpoints: mammalian dietary LC50endpoints fordifethialone and bromethalin•Toxicity endpoints based on administered dose, not bioavailabledoseLi it d d t / t i it d t il bl•Limitedpredator/scavengertoxicitydata available•Large range in LD50values within chemical, some spanning severalorders of magnitudeordersofmagnitude•Scaling factors provide adjustment for test animal body weights, butmay introduce additional variation among chemicals•LD/LC50estimates: some studies have low confidence in estimatedvalue as slope was very shallow15One-day exposure to baitToxicity endpointsConcentrationHalf-life in primaryScaledtoxicityof a.i. in bait1d d ti idconsumerSca ed o c yendpoints basedon body weights1-day rodenticideintake via allometricfood intake equationsDaily body-burden forsingle day incrementsBody burden after6 days bait intake1-day exposure RQsg bait consumed and days to reach LD6-day exposure RQs16gbaitconsumedanddaystoreachLD50Daily rodenticide intake based on...Bait concentrationChemical % a.i. mg a.i./kg-baitBrodifacoum0 00550.Difethialone 0.0025 25Warfarin0.025 2500.054540Chlorophacinone 0.005 50Diphacinone 0.005 50Bromethalin 0.010 100Allometric equations(USEPA 1993)•Estimation of daily feeding rates of a i for 3 weight classes of:Estimationofdailyfeedingratesofa.i.for3weightclassesof:•generic birds and passerines•generic mammals and rodentsD il db di t k17Dailydosebasedintake:dividing daily a.i. intake by body weight to obtainmg a.i./kg-bw/dayRQs based on one day dose-based(LD50) exposure in birdsBrodifacoumRQ = 0.5DifethialoneWarfarin (0.025%)Warfarin (0.054%)ChlorophacinoneDiphacinoneBromethalin0.001 0.01 0.1 1 10 100RQ1820 g100 g1000 gPasserine, adjusted LD50Generic, adjusted LD50Generic, unadjusted LD50Passerine, unadjusted LD50RQs based on one day dose-based(LD50) exposure in mammalsBrodifacoumRQ = 0.5DifethialoneWarfarin (0.025%)Warfarin (0.054%)ChlorophacinoneDiphacinoneBromethalin0.1 1 10 100RQ19Rodent, adjusted LD50Generic, adjusted LD50Generic, unadjusted LD50Rodent, unadjusted LD5015 g35 g1000 gSummary: one-day dose-based RQsDose-Based RQsDietary-Bait availability/ChemicalBased RQsBaitavailability/consumption rateOVERALL1 Day 6 DayBirdsBrodifacoumDifethialoneWarfarin (0.025%)Warfarin (0.054%)Chl h iChlorophacinoneDiphacinoneBromethalinMammalsBrodifacoumDifethialoneWarfarin (0.025%)Warfarin (0 054%)Warfarin(0.054%)ChlorophacinoneDiphacinoneBromethalin20All evidencesuggests riskPredominant evidenceof riskEquivocal evidenceof riskAll evidencesuggests low riskThere is apotential foraccumulation from day today......does it matter?...doesitmatter?21Six-day exposure to baitToxicity endpointsConcentrationHalf-life in primaryScaledtoxicityof a.i. in bait1d d ti idconsumerSca ed o c yendpoints basedon body weights1-day rodenticideintake via allometricfood intake equationsDaily body-burden forsingle day incrementsBody burden after6 days bait intake1-day exposure RQsg bait consumed and days to reach LD6-day exposure RQs22gbaitconsumedanddaystoreachLD50Chemical accumulation•Estimation of accumulated chemical loads(mgga.i./kg-bw) based on:•Daily feeding rates•Accumulation and elimination rates of chemicals•Whole-body elimination rates (half-lives) notavailable•Data available for liver and blood plasma halfDataavailableforliverandbloodplasmahalflives for most chemicals•Accumulation in body based on liver half-lives•Most values from one study to allow for method consistency•Bromethalin: blood plasma half-life, no liver data available•Used in primary and secondary exposure analysis23Half-lives for calculation ofdose accumulationRodenticide Test Species CompartmentEliminationhalf-life (days)B difMLi307 4roacoumousever.Difethialone Mouse Liver 28.5WarfarinMouseLiver66 8.Chlorophacinone Mouse Liver 35.4DiphacinonePigLiver5.5Bromethalin Rat Blood 5.624Liver and blood plasma half-livesB difroacoumDifethialoneWarfarinChlorophacinoneDiphacinoneBromethalin0.1 1 10 100 1000Liver half-life (days) used in accumulation calculationshalf-life, days-25Liverhalflife(days)usedinaccumulationcalculationsaccumulationcalculationsBlood plasma half-life (days)used in accumulation calculationsAccumulation equationdt=(FI*C / (wt/1000)) + d(t1)*e-kdt(FIC/(wt/1000))+d(t-1)ewhere:dt= dose (mg a.i./kg-bw) at daytFI f d i t k ( d t) b d ll t i tiFI=foodintake(g,dry wt)basedon allometric equationC = concentration of a.i. in bait (mg a.i./kg-diet)wt = weight (grams) of the bird or mammal consumerwt=weight(grams)ofthebirdormammalconsumerk = ln(2)/t1/2t1/2= half-life(days)ofchemical in liver(bloodforbromethalin)1/2ae (days) o c e ca e(b ood o b o et a )26Accumulation in 100 g generic bird100006-dayaccumulation1000Warfarin, 0.054%Warfarin, 0.025%100ChlorophacinoneBrodifacoumDifethialoneBromethalin

a .i./kg-bw10Diphacinone

mg a1270 5 10 15 20 25 30 35 40DaysRQs based on six day dose-based(LD50) exposure in birdsBrodifacoumRQ = 0.5DifethialoneWarfarin (0.025%)Warfarin (0.054%)ChlorophacinoneDiphacinoneBromethalin**0.001 0.01 0.1 1 10 100RQ2820 g100 g1000 g1-day exposure, adjusted LD506-day exposure, adjusted LD50**not expected to eat bait for 6 daysRQs based on six day dose-based(LD50) exposure in mammalsBrodifacoumRQ = 0.5DifethialoneWarfarin (0.025%)Warfarin (0.054%)ChlorophacinoneDiphacinoneBromethalin**0.1 1 10 100RQ291-day exposure, adjusted LD506-day exposure, adjusted LD50**not expected to eat bait for 6 days15 g35 g1000 gSummary: one- and six-day dose-based RQsDose-Based RQsDietary-Bait availability/ChemicalBased RQsBaitavailability/consumption rateOVERALL1 Day 6 DayBirdsBrodifacoumDifethialoneWarfarin (0.025%)Warfarin (0.054%)Chl h iChlorophacinoneDiphacinoneBromethalinNot assessedMammalsBrodifacoumDifethialoneWarfarin (0.025%)Warfarin (0 054%)Warfarin(0.054%)ChlorophacinoneDiphacinoneBromethalinNot assessed30All evidencesuggests riskPredominant evidenceof riskEquivocal evidenceof riskAll evidencesuggests low riskWhat if chemical wasincorporated in thedietary matrix......does that makea difference?31Exposure and toxicity values fordietary-based assessmentToxicityendpointConcentrationof a i in baitCalculate RQsLC(mg a i /kg-diet)y pofa.i.inbaitChemicalBait concentration(mg a.i./kg-bait)LC50(mga.i./kg-diet)Birds MammalsBrodifacoum501.330.53Difethialone 25 0.56 no dataWarfarin250625 5.4540Chlorophacinone 50 72 7.2Diphacinone 50 906 4.2Bromethalin 100 210 no data32RQs based on dietary (LC50) toxicityChemical Birds MammalsBrodifacoum38* 94*Difethialone45*no dataWarfarin (0 025%)0 4057*Warfarin(0.025%).Warfarin (0.054%)0.86* 123*Chlorophacinone0.89* 44*Diphacinone 0.0622*Bromethalin 0.48 no data* = exceed acute risk LOC(0.5)33( )Summary: all RQ analysesDose-Based RQsDietary-Bait availability/ChemicalBased RQsBaitavailability/consumption rateOVERALL1 Day 6 DayBirdsBrodifacoumDifethialoneWarfarin (0.025%)Warfarin (0.054%)Chl h iChlorophacinoneDiphacinoneBromethalinNot assessedMammalsBrodifacoumDifethialone No dataWarfarin (0.025%)Warfarin (0 054%)Warfarin(0.054%)ChlorophacinoneDiphacinoneBromethalinNot assessedNo data34All evidencesuggests riskPredominant evidenceof riskEquivocal evidenceof riskAll evidencesuggests low riskRQs say concerns exist forrodenticides...but will non-targets...butwillnontargetsreally be exposed toenough bait toexperience toxicity?35experiencetoxicity?Bait consumption opportunity...Toxicity endpointsConcentrationHalf-life in primaryScaledtoxicityof a.i. in bait1d d ti idconsumerSca ed o c yendpoints basedon body weights1-day rodenticideintake via allometricfood intake equationsDaily body-burden forsingle day incrementsBody burden after6 days bait intake1-day exposure RQsg bait consumed and days to reach LD6-day exposure RQs36gbaitconsumedanddaystoreachLD50How much bait does a 100 g bird needto consume?(part 1)1000(p )Warfarin, 0.054%100Brodifacoum

a .i./kg-bw10

mg1) Is body?2) YES–calculate101234567891011burden≥LD50?2)YES–calculategrams bait needed toreach LD50.0123456789101137DaysHow much bait does a 100 g bird needto consume?(part 2)10003) NO. Is bodyburden≥LD?(p )Warfarin, 0.054%1) Is bodyburden≥LD50?burden≥LD50?100Brodifacoum

a .i./kg-bw2)NO. Is body3) YES. For day 6, bodyburden is > LD5010

mg a) yburden≥LD50?4) Grams bait consumed=1012345678910114)Gramsbaitconsumedbait intake for 1 day x 6 days3801234567891011DaysBirds: grams bait to reach bodyburden equivalent to LD50Brodifacoum1 day feed1 day feedDifethialoneWarfarin (0.025%)5 days42 daysWarfarin (0.054%)Chlorophacinone19 days3 days5days17days>365 daysDiphacinoneBromethalin19days>365 daysy>365 days0.1 1 10 100 1000 10000 100000grams bait consumed3920 g generic birds1000 g generic birdsgramsbaitconsumedMammals: grams bait to reachbody burden equivalent to LD50Brodifacoum1 day feed1 day feedDifethialoneWarfarin (0.025%)Warfarin (0.054%)Chlorophacinone2 days2 daysDiphacinoneBromethalin2days2days0.1 1 10 100grams bait consumed4015 g generic mammals1000 g generic mammalsgramsbaitconsumedPrimary Exposure: Summary of ConcernsDose-Based RQsDietary-Bait availability/ChemicalBased RQsBaitavailability/consumption rateOVERALL1 Day 6 DayBirdsBrodifacoumDifethialoneWarfarin (0.025%)Warfarin (0.054%)Chl h iChlorophacinoneDiphacinoneBromethalinNot assessedMammalsBrodifacoumDifethialoneNo dataWarfarin (0.025%)Warfarin (0 054%)Warfarin(0.054%)ChlorophacinoneDiphacinoneBromethalinNot assessedNo data41All evidencesuggests riskPredominant evidenceof riskEquivocal evidenceof riskAll evidencesuggests low risk