Reconstruction of methylmercury intakes in indigenous populations from biomarker data

HealthCanada,ChemicalHealthHazardAssessmentDivision, BureauofChemicalSafety,FoodDirectorate,SirF.BantingBldg, Tunney’sPasture,Ottawa,Ontario,CanadaK1A0L2Significantamountsofmethylmercury(MeHg)canbioaccumulateinfishandseamammals.TomonitorMeHgexposureinindividuals,organicandinorganicmercuryareoftenmeasuredinbloodsamplesorinhairstrands,thelatterbeingbyfarthebestintegratorofpastexposure.Withknowledgeo ftheMeHgkineticsinhumans,thelevelsofbothbiomarkerscanberelatedtoMeHgbodyburdenandintakes.Inthepresentstudy,weusethetoxicokineticmodelofCarrieretal.(2001)describingthedistributionandexcretionofMeHginhumans,toreconstructthehistoryofMeHgintakeso findigenouswomenoftheInuvikregioninCanadastartingfromtotalmercuryconcentrationsinhairsegments.FromthesereconstructedMeHgintakes,thecorrespondingsimulatedmercurybloodconcentrationsarefoundtobegoodpredictorsoftheconcentrationsactuallymeasuredinbloodsamples. Animportantconclusionofthisstudyisthat,foralmostallsubjects,thereconstructedhistoryoftheirMeHgintakesprovidesmuchlowerintakevalue sthanintakesestimatedfromquestionnairesonfoodconsumptionandestimatedMeHglevelsinthesefoods;themeanvalueofthereconstructedMeHgintakesis0.03mg/kg/daycomparedwiththemeanvalueof0.20 mg/kg/dayobtainedfromquestionnaires.Themodelwasalsousedtoback-calculatetheMeHgintakesfromconcentrationsinhairstrandscollectedfromaboriginalsoftheAmazonregioninBrazil,apopulationsignificantlymoreexposedthanthepopulationoftheInuvikregion.Journal of Exposure Science and Environmental Epidemiology (2006)16, 19–29.doi:10.1038/sj.jea.7500433;publishedonline29June2005Keywords: methylmercury,biomonitoring,toxicokinetics,biomarker.