Document 0JmYwvGnx8GLqnng1G4poYe2R

> i 9 General Offices tf April 25,2001 we wr AR 226 _ 1015 Mr. Charles Auer OfficeofPollution Prevention and Toxics U.S. Environmental Protection Agency 4W0a1shMingSttorene,t DS.CW. 20460 gE an ZR 8ow E=X Re: Serum Half-Life of Perfluorooctane Sulfonate 2 5 Dear Mr. Auer "This with will you, sOusmcmaarrHiezrenathnededzi,scMuiscsihoanelduSrainntgoroourancodnmfeerernecgearcdailnlgonneMwaricnfhor1m9a,t2i0o0n1 obtained as part of the ongoing serum half-life study on PFOS. SAuslfyoonuatken(oPwF,O3S)Mihnassebreuemnoafttreetmiprteidnwgotrokecrasl.culWatee haahvaelfp-lriefveiofourslpyerrfelpuoorrtoeodcotanntewo idinftfeirciumltdtaotainsteetrs.pret3.MThhaesycodnotinantuecdartroasbtaurdaytethoiusripssruieo.r cCaulrorvelnattliyonsavailable data are In January 1999, 3M half-life for PFOS in prertoivrieddewdorEkPerAs'wistehrluimmiotfedapdpartoaxfirmoatme3lywo1r,k4e0r0sdaiynsd.ica3tiMnghaad oiinn psreorguremshsalafllairfgeerofstPuFdyO,SaandmoonngJu2l7y r1e3t,ir2e0d0e0m,plsouybemeist.tedThtheesefiresmtpilnotyereiems rheapdort worked at 3M's Decatur, Alabama and Cottage Grove, Minnesota manufacturing plans. M"Tahiys i1n9it9i9alaanndalNyosivseomfbtehre 129799re,tdireeseisgunsateedddtaot,aipoainndtst2.colUlseicntgedaionnNeo-vcoemmpbaerrtm1e9n9t8, `dmaoydsel(,ratnhgeem1e3a9n-s6e4r0umdahyasl)f. lfTehdeerteemramiinniendgfo9re1m8polfoytehees27ciethmeprlhoaydeelsesws atsha3n0t3hree dwaatsa ipnoiitniatlslyorredpiodrtneodt sfohrocwyanotmreonldg.usThperi3m0a3tedsa(y2s7w4adsaynse)a.r Athlethsoeurguhmhwalefwleirfee that aiwmaprreoovfemseenvteroavlelrimoiutratpiroenvsioinustheisstismtuadtye., b3aMsecdonosnidoenlryed3tehmepilnotyeereims,daatnadtuosbiengan Varying advised analytic caution techniques for in interpreting determining PFOS. the limited data set. However, the Interim Report rSeetruurmnewdassevceorlallecmtoendtihnsMlaatyer 2000 and for a fourth data point (1). showed results inconsistent Initial analysis was with those expected. Tahnailsytciacusteedchunsiqtuoereexehxiabmitisnevoafrisaobuilrictyesofof20ertroor3i0n%thwehleanbotrhaetosraymmeeassaumrpelmeenist. The Contain I ' Me. Charles Auer April 25, 2001 Page 2 `measured at different time points. The best way to reduce this variability is to run all samples from one subject during one analytic run. Random errors represent another typeof error, and multiple analysis of the same sample can be used to reduce errors from this source. Nine of the 27 subjects, representing a range of PFOS values, were selected for reanalysis. Triplicate analysis was done for all time points (to through t;). All samples for each subject were analyzed during one analytic run. In this way, controllable sources of variability were reduced. Preliminary analysis of these data does not corroborate the range for serum half life reported in the first Interim Report. The data from these nine subjects forto through t; suggest a minimum half life near 1500 days, but we are still exploring various issues that confound interpretation of the data. Other factors complicating assessment of the serum half-life in retired workers may include the possible presenceofother fluorochemicals from occupational exposure that may be metabolized to PFOS during the study; ongoing non-occupational exposure during the study; or difficulty deriving average valuesifthe elimination kinetics are concentration-dependent, since the workers began the study with varying levels. At this point, the caution admonished in both 3M's Interim Report and the October 2000 draft OECD Initial Assessment is appropriate. Neither the current calculation nor prior values should be considered conclusive estimates. xtra or an wh whl nb de hwy 245 We plan to submit a second interim report in the summer of2001. Our plan after that, however, is to collect data for a periodof at least two years and possibly longer laboratory variability as much as possible. Although this typeofstudy continues to carry many limitations, it remains a good opportunity to measure human serum half life, albeit at concentrations many times higher than those observed in non-occupationally exposed individuals. Please do not hesitate to contact me if you have any questions. Soy RIpbd Very truly yours, Mi, MPH gre LarryRl Zob, M.D, MPH. Medical Director c: Mr. Oscar Hernandez Mr. Michael Santoro ES