Document nkwG7nJNJqvd7eV1VBJBak9JR

e ehponi,ne.org Al226-354p7t EHENAVLITRHONMENTAL PERSPECTIVES Accumulation and Clearance of PFOA in Current and Former Residents of an Exposed Community Ryan Seals, Scott M. Bartell, and Kyle Steenland doi: 10.1289/ehp.1002346 (available at http://dx.doi.org/) Online 22 September 2010 ah [rita -- p2 Page tarsi Manuscript Title: Accumulation and Clearance of PFOA in Current and Former Residents of an Exposed Community Author Names: Ryan Seals', Scott M Bartell, Kyle Steenland" "Department of Environmental and Occupational Health, Emory University, Atlanta, GA cAProgram in Public Health and Department of Epidemiology, University of California, Irvine, Corresponding Author: R1y51a8n CSleiaflison Road NE, Alana, GA 30322 cp..r4s0e4a.l7s2@7h:s5p3h68harvard du ..440044--742572.-81794640 1 3 Page 30133 Abstract Background. PFOA is a perfluoroalkyl acid found in over 99% of Americans. Is health effects are unknown. Prior estimates of serum half-life range from 2.3 0 3.8 years. Objectives. To assess the impact of years of residence and years since residence on serum PFOA. concentration in a sampleofcurrent and former residents of six water districts in West Virginia. and Ohio exposed to PFOA emissions from an industrial facility. Methods. Serum samples and questionnaires, including residential history, were collected in 2005-2006. We modeled log serum PFOA (ng/mL)forcurrent residents as a function of years of residence in a water district, adjusted for a variety of factors. We modeled the half-life in former tesidents via a two-segment log-linear spline in twowaterdistricts with high exposure. Results. We modeled serum PFOA concentration in 17,516 current residents as a function of years of residence (R'=0.68). Years of residence was significantly associated with PFOA concenteation (1% increase in serum PFOA per year of residence), with significant heterogeneity by water district. Half-life was estimated in two water districts comprising 1,573 total individuals. Years-since-residing in a water district was significantly associated with serum PFOA, yielding half-lives of 2.9:2nd 8.5 years for water districts with higher end lower exposure. levels, respectively. Conclusion. Yearsofresidence in an exposed water district was positively associated with `observed serum PFOA in 2005-2006. Differences in serum clearance rate between low- and 3 Running Title: Accumulation and Clearance of PFOA in a Community Key words: PFOA. C8, PFA, serum levels, half-life, water contamination pd Page2or33 Acknowledgements/Grant Support/Competing Financial Interests Declaration ``TChoiusntrye,scWaVrc.h UisSAfu)ndbeedtwbeyenthDeuCPo8ntClaasnsd AplcatinitoinffsS.etFtulnedmsentweArgeraedemmiennistte(rCierdcubiyttChoeuGratrodfenWoCiotdy Group (Melville, cither party to the NlaYw)suitth.at reports to the court. Our work and conclusions are independent of `The authors declare they have no competing financial interests. Abbreviations: PFOAICS - Perfluorooctanoic acid | PPAR - Peroxisome proliferator-activated receptor alpha 2 pS Page 40133 high-exposurewaterdistricts suggest a possible concentration-dependent or time-dependent clearance process, or inadequate adjustment for background exposures. a p.6 Pagesof3: Introduction Perfluorooctanoic acid (PFOA, or C8) is a perfluoroalky acid used in the production of many fluoropolymers including non-stick cookware, waterproofing, and flame retardants (Kennedy etal. 2004). Not naturally occurring, PFOA has been found in nature around the world, in multiple species, and in over 99% of serum samples obiained from the 2003-2004 National Health and Nutrition Examination Survey (Calafat ct al. 2007; Houdeetal. 2006). Despite recent regulatory and industrial efforts to phase out production and use by 2015, PFOA accumulates and persist in the environment, and human exposure is not expected to cease for some time. Studies in rodents suggest that PFOA may be associated with many disease outcomes, including increased hyperplasias and benign tumors of the testicles, liver, and pancreas, low birth weight, decreased immune response, and decreased cholesterol (Hines etal. 2009; Kennedy etal. 2004: Lau et al. 2007). However, the appropriatenessoftheanimal models has been called into question becauseofthe wide rangeofclearance rates observed between and within species, and becauseofspecies-specific differences in the ole of the PPARa-mediated effects of PFOA (DeWitt etal. 2009; Lau etal. 2007: Rosen et al. 2009). Human studies of PFOA have been thus far largely fimited to cross-sectional studies and retrospective analyses of occupational cohorts. To date no clear health effects of PFOA have been established, but studies 5o far are sparse. Average concentrations of 3.9 ng/mL (equivalent (0 parts per billion) were found in a nationally representative sample of US citizens in 2003-2004, with higher levels in males and whites (Calafat ct al. 2007). Levels ranging from 100 t0 5,000 ng/mL have been observed in `occupational cohorts (Lau et al. 2007; Lundin et al. 2009; Olsen and Zobel 2007). 5 7 Pager 33 "The current study population is derived from the C8 Health Project, which has been described previously (Frisbee etal. 2009). The C8 Health Project collected data on 69.000 current and former residents ofthemid:Ohio valley who had been exposed to PFOA via contaminated drinking water. The average serum PFOA in this population was 82 ng/mL, with a median of 28 ng/mL (Stcenland etal. 2009). Establishingtherate of clearance of PFOA from the body is important for retrospectively determining lifetime exposure levels and for predicting future serum concentrations. PFOA is known to persist in human serum long after exposure has ceased, and is not metabolized in the body (Kennedy et al. 2004). Current estimates of serum half-life are derived from thrce primary sources. A study of 26 former employees of a manufacturing facility that produced PFOA, with a mean initial serum concentration of 799 ng/mL. estimated an average half life of 3.8 years (95% CI: 3.04.1), with individual hallives ranging from 1.5 109.1 years based ona five year followup (Olsen etal. 2007), A more recent study of PFOA levels in 138 residents oaf German community following implementationofcharcoal filtration estimated a mean half-life of 3.26 years (range 1.03-14.67) (Brede etal. 2010). Finally, an ongoingstudyof 200 community residents livingnear a PFOAfacilityand partofthe C8 Health Project (a subsetofthe same population studied here) were followed for one year and, based on multiple blood samples and & `mean initial serum concentration of 180 ng/mL, exhibiteda half-life of 2.3 years (95% CI: 2.12.4) (Bartel et al. 2009). Half-life estimates based on only one year of follow-up must be: considered with caution. Preliminary results indicate that a traditional exponential decay model is sufficient for describing the clearance of PFOA from the body, despite earlier indications that clearance mayoccur in 4 time-dependent fashion in animals (Tacnt al. 2007). 6 ps Page7o133 `Our goal in this study was to estimate the effect of duratio ofresidence on PFOA levels among current residents and toestimatethe effect of yearssince-lcaving among former residents. The ater goal also involved estimating half-life. While useofcross-sectional vs. longitudinal data to estimate half-life is not optimal it can provide useful information. 7 Ix] Page of 33 Methods Data source. The C8 Health Project was conducted between August 2005 and August 2006. and collected health data from current and former residentsofthe study area using an extensive questionnaire and blood test, including the serum concentration of PFOA (n=69.030). fuller description of the study has been published previously (Frisbee et al. 2009). The questionnaire, in addition to basic demographic information, included an extensive residential History beginning in 1980, and included information on water consumption source at cach address (public/private, tap/bottled water). The questionnaire also queried individuals about behaviors including smoking, alcohol consumption, and vegetarianism. Studyparticipants. We identified individuals from the C8 Health Project who had consented to further follow-up and release of identifiable dat to us. and who had provided residential history during the C8 Health Project (n=48.880). As noted, our goal was (0 study the effectofduration of residence in a water district, and of years-sinceleaving a water district, on PFOA levels measured in 2005-2006. deally for our `purposes, water within a water district would have had a constant levelofcontamination over time, 50 that yearsofresidence would reflect aconstant exposure. In practice, PFOA emissions from the plant increased over time, peaking in the 1990s. In addition,different water district are Known to have differcat levelsof contamination, largely dueto distance from the plant (Steenland etal. 2009), `We first excluded individuals who had aselfreported history of employment by DuPont because oflikely high exposure levels at the chemical plant (5%). We then excluded those who had a history of residence in more than one water district (25%): ever reported a private well as 8 p.10 Page sar 33 thei primary source ofdrinking water (11%): or reported intermittent residence in the water district of interest (9%). These exclusions were motivated by the desire for subjects to have `continuous exposure 10 a single source of exposure, within single contaminated water district Because the limitofdetection for serum PFOA was 0.5 ng/mL we also excluded individuals at or below this level (2%). Finally, we excluded individuals who reported overlapping residences in their residential history (3%). After al exclusions, 19.460 subjects remained for analysis. (Curren residents. After the above exclusions. , we identified individuals who were residing in one of the six wate districts on the date of interview and esting ("current cesidentsTM; 1=17.516). The focusof the analysisofcurrent residents was the effectofcumulative years lived ina water district. Former residents. We studied a group of former residents to determine the effect of years-since-leaving on PFOA measured in 2005-2006 and to estimate half-life. We limited our analysis of former residents 0 the two water districts of Little Hocking and Lubeck, because. these districts are hypothesized to have higher levels of exposure and half-life could be more reliably estimated. In addition tothe above criteria forcurrent residents, among former residents we excluded individuals with less than 2yearsresidence in 2 water district (11%). and a serum PFOA concentration lower than 15 ng/mL (28%). These criteria were used to limit the analysis individuals who (1) had enough history in the water distictot build up substantial levels of PFOA, and (2) had sufficiently high baseline POA concentrations, such tha they had not reached background levels of PFOA by the interview date. The final cohort of former residents consisted of 643 Litle Hocking residents and 1.029 Lubeck residents. Statistical analysis 9 p11 Page 100133 General models without exposure termsofinteres. For all analyses, based on normalizing residuals for skewed data and in accordance with prior published results (Steenland et al. 2009), we modeled the natural logarithm of PFOA as `measured in 2005-2006 2s the outcome ofa linear set of predictors. Variables considered as potential covariates were: sex, age, race (white vs. non-white), BMI, growing one's own vegetables, vegetarianism, alcohol consumption, current and former smoking, regular exercise, and use of boiled wateras primary source of drinking water. These variables were all measured in 2005/2006. and had been used in prior analyses of PFOA levels (Steenland et al. 2009). Age, BMI, and date of interview were categorized as previously (Steenland etal. 2009). Forthe analysis of current residents, with six water districts, using a backward selection process with a cutoffof0.10 and without including duration of residence (our principal variable oFinterest) we created models individually for cachofthe six water districts, odetermine which covariates would be included in (inal models. The backward selection process iteratively fit `models, dropping the least significant covariate at each step until all were significant at the cutoff evelof0.10. In analyses with the six water districts combined, we added an indicator variable for water district 0 the model, which allowed us to determine the relative importance of residence in a particular water district, as well as the effect of having resided in that district, "This process was repeated for the analysis of former residents which was restricted 10 two water districts. Analysesfor durationofexposure "The goal of the first analysis was to estimate the relationship between duration of exposuretopublic water withina district and the measured serum PFOA level in 2005or2006 10 p12 Page 110133 For this analysis we considered only individuals residing inth six water districts onthedate of interview and testing (current residents). Cumulative years in the water district was analyzed as both a continuous and categorical variable In(PFOAs) = a + f+ CUM YEARS +5-X [1] where CUM YEARS represents the number of years lived i the water distict, and & and X are parameter and covariate vectors. Analyses byyears since leaving (half-ie analysis) A second analysis was performed Lo estimate the half-life in former residents only (restricted to two water districts), via analyzing the relationship between the number of years since living in the water district and the measured serum PFOA level in 2005 or 2006, using the following model: In(PFOAus 5) = a + fy - YEARS SINCE+f, CUM YEARS +3-X [2] where YEARS SINCE represents the number of years elapsed since residence in the water district, `CUM YEARS is the number of years lived inthe water district, and 8 and X are parameter and covariate vectors. This analysis was restricted t0 two water districts which had the highest levels, 50.25 10 avoid as much as possible the problem of background levels affecting our estimation of theelimination parameter (3). In this analysis, we sublracted background level5s ng/mi) from ll subjects, and required that all subjects had at least 15 ng/ml PFOA in 2005. Although performed on a single cross-sectional measurement of serum PFOA, rather than the more traditional longitudinal analysis of repeated measurements,the analysis byyearssince leaving can provide an approximationoftheclearance rate of PFOA,. The number of years 1u p13 : Page 120133 elapsed since living in the water district was analyzed as both a continuous and categorical variable. "The half-life of a serum concentration describes the number ofyears required for the concentration required t reach one-half of the baseline level Elimination of a substance from the circulatory system s usually described by a logarithmic process, where the concentration of the substance at tim(Ce) i elated tothe baseline concentration (Co) bythe time-dependent term *, where Ais a positive decay constant ie. C= Coe". Tis is called a ist order elimination in which the rate of elimination is constant and docs not depend on initial `concentration. To obtain the halflife (1). we scek the time required such tht C, is of Co. or (2) such that 4*Cy= Coe". Rearranging, we have: ta ==()4 3) "The slope ofthe line describing the relationship between YEARS and In(PFOA) is , whichis equal (0. in equation 3 above (also see below), and fence can be used o solv for the estimated number of years that would be required for the PFOA to fal by half. Since by model 2) we have predicted PFOA=e* "YEARS SINCE and. given tha some change in YEARS SINCE will cut predicted PFOA in haf, we haveVase?"YPARS SNCEL- YEARS SNCED, ince he intercept and covariate terms cancel out. The change in YEARS SINCE is then the halF-fe, and taking the Tog ofthe last expression we regain model (3) and have 05)=f12 4) wherefs equivalent to. 12 p14 Page 130133 `Graphing a scatter plot of log PFOA by YEARS SINCE, we found an apparent non-linear elationship usinag LOESS non-parametric curve. We then modeled the relationship usinag two-segment linear spline (Steenland and Deddens 2004). The spline is included in the model through the addition ofa time-dependent variable that is zero prior to the knot and increases after the knot. Below is an example, with a knot at YEARS SINCE=4: INPFOnAs = 5) = a + fi YEARS SINCE + fy max[O(VEARS SINCE ~4)) + fs - CUM YEARS +3-X [5] The expression max[0.(YEARS SINCE - 4)] evaluates to 0 whenYEARS SINCE <4 nd equals (YEARS SINCE 4) when YEARS SINCE > 4. The slopeof the regression line is therefore Bi prior the knot, and (Br+fz) after the knot. We chose the knot basd firs on visual inspecion of therelationshipbetweenyears clapsedand In(PFOA), to determine th likely region of interest, followed by an erative procedure where we picked the knot with the best model likelihood. We used an F-test test the increase in the goodness-of-fint the spline model over the linear model. Outliers with absolute studentized residualsgreaterthan 3 were discarded (0.5%). Prior work has suggested that half-life estimates aftr truncationtoaccount for nearbackground levelscan introduce bias (Michalek et al. 1998). We performed a sensitivity analysis using various truncation values (serum PFOA concentrations below the truncation value were. discarded) to assess the robustnessofour half-life estimates, retaining the same models and knot Tocations as in th initial analysis with truncation at 15 ng/mL. In al analyses, 5 ng/mL was subtracted after truncation and before regression. "The method for ascertaining the serum concentration of PFOA has been described previously (Frisbee et a. 2009). This study was approved by IRBs at al C8 Science Panel 13 p15 Page 140133 institutions, and all applicable requirements for human research were me. All participants gave writien informed consent o participate in the C8 Health project: consent procedures have been described previously (Frisbee etal. 2009). Al analyses were performed using SAS v9.1 (Cary, NC). Images were generated using PASW v17.0 (Chicago, IL). 1 p16 Page 15.0133 Results Median levels ofPFOA for current and former residents are shown in Table 1. In residents tll residing in the six wate districts at the time of the interview, differences in serum PFOA levels were apparent across wate distics, sex, useofbotled water, growing own vegetables, smoking history, and date of esting, similar to results reported previously for the entire C8 Health Study cohort (Sicenland etal. 2009). Thesubset of 1,672 former residents had higher PFOA levels than the current residents because this subset was limited to residents of Little Hocking and Lubeck, the two highest-exposed water districts. Curren Residents. Figure 1 displays the relationship between cumulative ears of residence in the six water districts and the natural logarithm of serum PFOA (ng/mL), in individuals reporting residence in one of the ix water disticts on the dat of interview in 20052006 (current residents). The positive slope i significant a th p<0.001 levelfo all ix districts. "The effect of cumulative years is reasonably linear with In(PFOA). "The results of the full model afer backward selection, with an indicator variable for water district, are shown in Table 2. The R-squared for the full model was 0.68. Waterdistrict residence explained the majorityofthe variance (partial R-squared), with residence in Little Hocking alone accounting for 394%. After residence, cumulative years of residence explained 1.5% of the variance. Previously observed associations were also replicated: higher levels in males, a U-shaped relationship with age, higher levels in current vs never smokers, and higher levels in those who grow their own vegetables (Stcenland etal. 2009), The average increase in PFOA levels for each year of residence in a water district was 1:29% (95% CI: 11-14%). However, because exposure levels are known o bedifferent betwen 15 pA? | Page 16.0133 water districts, and because median serum PFOA levels differed so greatly bywaterdistrict, we fit models for each water district separately (0 yield disrict-specifc effects of cumulative residence (Table 3; Fest for six interaction terms significant at p<0.001). As expected, districts with the highest exposure levels display the largest relationship between years of residential history and serum PFOA. In Pomeroy and Mason County, the districts with the lowest exposures as measured in current residents, the effec of years of residence was least. Former residents. Using a two-segment linear spline regression with the same variables as above, we obtained estimates for the effect of years elapsed since residence on In(PFOA) for the two segments of thesplinecurve. Based on visual inspection ofaLOESS curve and `goodness-of-fit statistics comparing various possible knots, we chose four years a the knot for Little Hocking and nine yeaasrthse knot for Lubec. Figures 2a and 2b show the plots and fited lines for the two water districts. An Fest for reduction in model erro after moving from | segment (standard linear regressiotno) 2 segments was significant atp<0.001 for both water districts, and overall model fit (Rsquare) increased by 4% in Little Hocking and 3% in Lubeck after inclusion of the spline. A three-segment incar spline was nota significantly better fit 0 the: data in either water district. "The estimated half-lives and percent change in PFOA by yearfor the twolinesegments in each water district are shown in Table 4. Because the half-lives are calculated from the slope, they represent the half-life that would result if the instantaneous rateofclearance were 0 continue indefinitely. The shallower line afte the kno likely reflects either the gradual slowing. of PFOA clearance over time (Lite Hocking) and/or the decline of low exposures to near background (15 ppb) inthe case of Lubeck. For example, an individual from Little Hocking with an initial serum PFOAof 55 ng/mL would have a concentrationof 21 ng/mL afer four years 16 p18 Page 170133 (21%reduction per year). and aconcentration of 15 ng/mL. four years later (8% reduction per year). The resultant half-lives for Lite Hocking were 2.9 and 10.1 years forthe two spline segments. while for Lubeck they were 8.5 years in the initial spline segment and undefined for the second segment (the estimated parameter was 0.0021, or approximately 0, indicating no furtherdecrease in PFOA levels over time). Our estimated half-lives were sensitive o the truncation cutpoint we used. below which subjects were excluded on the bass tha they were nearbackground levels. Table 5 displays various halF-fife estimates for the first spline segment in Little Hocking and Lubeck afer various truncation values were applied. Lite Hocking half-life estimates ranged from 2.5 10 3.0 years, while in Lubeck estimates ranged from 5.9 0 10.3 years At all truncation values the half-life in Litle Hocking was lower than in Lubeck, with larger discrepancies at higher truncation values. Because former Lubock residents had lower serum PFOA concentrations, more individuals were discarded from Lubeck at all truncation values, With the discrepancy larger at higher values. Our estimated half-lives were also sensitive to the amount we subtractedoffof our PFOA. levels, a subtraction designed to eliminate background levels in estimating half-life. To tet the robustnessofour estimate 0 this subaction, we performed asimilar analyss that climinated all individuals below 15 ng/mL in 2005, and subiracted 15. cather than 5, fromtheir measured value. Results wece similar 10 our original results: the estimated half forthe fist four years of clearance in former residents of Lille Hocking was 3.0 years, while for Lubeck (for the first nine years) it was 9.4 years. PFOA clearance appears to be sex-dependent in rais (with a much longer halflife in males), but not in monkeys (Lau etal. 2007). In our daa for Lite Hocking, males were associated wiaftasther rate of clearance (p=0.02), but only in the fist four years. Annual 17 p.19 Page 180133 reduction in scrum PFOA was 27% in males vs. 18% in females. Theeffect was non-significant after four years. However, prior longitudinal analysesof200 residents in Lite Hocking and Lubeck found no sex differences in half-life (Bartel et al. 2009). We did not observe sex differences in former residentsofLubeck. 18 p.20 Page 190133 Discussion `We founad significant positive association between years of residence in an exposed water district and serum PFOA, with an average of 1% increase peryear of residence. Lower levelsofserum PFOA in former vs. current residents residence has been demonstrated in this `cohort previously (Steenland ct al. 2009), but this analysis now demonstrates a significant trend within current residents (those still residing in exposed water districts in 2005-2006 based on their prior residential history). We also found a more substantial relationship between PFOA and years of residence in water districts closer (0 the industrial facility, as expected. After water district, years of residence accounted for the greatest variance in the ited model. These findings provide preliminaryjustification for possible useofresidential history asa proxy for prior exposure in epidemiologic studies. In former residents the main finding from our analysis was that the use ofa two-segment spline increased the model it and better approximated the observed relationship than simple linear model. In both water districts,an apparent nonlinear relationship resulted in asignificantly Tower clearance rat afte the knotofeithe4r or9 years. Ifourassumpatreicoorrnecst tis implies thata simple irs order elimination model may not hold, and thattherate of elimination may be concentration-dependent or time-dependent. We feel that the results suggest both a concentration- and time-dependent relationship because the time factoristhe same for both Lite Hocking and Lubeck (years since former residence), but exposure was lower in Lubeck. However, the apparent time-dependent relationship could also be due to the concenteation decrease over time. Its intresting tha the rate of decay (slope) of the second linear segment for Little Hocking is similar to the rate of decay for the first segment for Lubeck, at similar `concentration levels. Inourcohort, former residentsofLittle Hocking had PFOA levels roughly 19 p21 Page 200133 twice as high former residents of Lubeck.Ifserum clearance were concentration-independent the equation describing the relationship between PFOA and years living in the district and years elapsed since living in district would be the same in Lite Hocking and Lubeck. Furthermore, within each water district the decay in In(PFOA) would be linear rather than exhibiting a lower slope at lower concentrations. As in prior studies ofthis population, we observed decreasing serum concentrations cross dates of testing (Stcenland ct al. 2009). This may be du to behavior modification as the `ptative health effects of PFOA became publicized, both i increased bottled water usage and decreased tap water consumption. We observed a light increase in reported botled water usage. over the testing period, and Little Hocking was offering free bottled water 0 individuals. Additionally, iti plausible that those who tested earliest were those who lived closer o the industial facility and in morehighlyexposedwater districts,However, adjusting for date of testing did not significantly alter anyofour parameters of interest. Prior studies in humans have found no difference in clearance rates between men and women, but animal studies have suggested that females may be more effective elearers of PFOA (Bartell ctal. 2009; Bredeetal. 2010; Lau et al. 2007). Harada etal. demonstrated in moderately exposed city-dwelles that renal excretion rates in both males and females were negligibly small, but that female clearance maybe age-dependent (Harada et al. 2005). In our cohort we observed Tower PFOA levels in females, an observation consistent with prior studies in this cohort and others (Calafat ct al. 2007; Steenland et al. 2009). However, we observed a significantly faster clearance rate in men in the initial years of former Lite Hocking residents. This calls into question the assumption that lower levels in females are du to faster rate ofclearance, but we cannot rule out that the apparent sex effect is due to concentration. 20 p22 Page 210133 "This study has three major limitations. The first is the cross-sectional nature of the analysis. Particularly in the estimation of half-life, this limited our ability 0 draw inferences from the analysis. Although cross-sectional halflife estimation has been used in an analogous setting for urinary bisphenol A aftr fasting (Stahlehtuatl.2009), traditional half-life studies follow individuals over time, allowing researchers to compare serum concentration at any point in time to th intial concentration. Cross-sectional analyses must ely on model-based estimation of the inital concentrations insteadofdirectly observed values. Out regression model included years of residence in the contaminated water district, sex, age, growing own vegetables, smoking, and consuming bottled water. We relied on recall via questionnaire to develop prior residential history. In addition to missing and incomplete data (gaps in residential history, which led 10 the exclusionofsome subjects rom the analysis), there is the possibilty that individuals misteported their water district andlor years of residence. "The second major limitation is the implied assumption that exposure was uniform within a waterdistrict,both between individuals and over time, which we know to be false. Although we excluded individuals who were employed by DuPont or who reported private well use to limit the heterogeneity of the population, individual exposure was undoubtedly varied based on geographical location, individual behavior, and other uncontrollable factors. Also, we know that PFOA emissions from the plant were not constant over time and peaked in the late 19905, but we. were unable to account for this without queniitative estimatesofannual water system concentrations. Further studies ofthis population will make use of advanced exposure models that aceount for both individualand temporal variations in exposure. A third major limitationof our analysis is the potential bias introduced by the exclusion of participants with serum levels below 15 ng/mL. Truncation below a fixed concentration 2 p.23 Page 220133 threshold is known to introduce bias in half-life estimates for longitudinal data (Michalek et al. 1998). and is likely to have a similar effec in cross-sectional analyses. Although restricting the analysis to individuals with PFOA serum concentrations below 15 ng/mL avoids one typeof bias (overestimationofhalf-lives among participants whose PFOA serum concentrations are no toner in decline by the time of the serum sample). it is likely to introduce another type ofbias resulting in overestimation ofhalf-lives, because excluded participants are likely to have shorter half-lives on average than retained participants. Our sensitivity analysis using different truncation values resulled in a smaller range of values for the more highly exposed residents of Little Hocking, while the half-life in former Lubeck residents was more sensitive to the truncation value. Notably, Lubeck residents tended to have lower concentrations, so truncation at ll values resulted in more individuals discarded from the Lubeck analysis, withaprogressively larger difference at higher truncation values. A minor limitationof this study was the inability to differentiate between variable `exposure levels and accumulation duc to constant exposure. However, because emission levels and predicted water concentrations were Known to be variable over the study period, peaking in the late 1990s. we feel that some of the annual increase as shown by th significance of years of residence is fikely due to increasing exposures, rather than approach 10. steady-state (Paustenbach etal. 2007). Further work wil be done with exposure estimates that vary by year and location of residence. These results suggest that the half-life for PFOA lcs between the previously reported estimates of 2.3 and 3.8 years for more highly exposed individuals, but that serum clearance of PFOA may be concentration-depender. 2 p.2 Page 230133 References Bartell SPMF,OCAalCaofnactenAtMr,atiLoynusCa,fteKratGoraKn,ulRayraAnctPiBv,atSetdeeCnalrabnodnKF.il2t0r0a9t.ionRaatteTowfoDePculbilniec WinatSeerrum Brede ES,yWsitlehmeslimn MO,hiGoeanndTW,eMsatlVliregJri,niRaa.ucEhnfvuisrsonK,HeKarlatfht Perspect M, ct al. 118(2):222-228. 2010. Two-year follow-up rbeidoumcotniiotnoriinnpgubpliiloctwsattuedrysoyfrsetseimdeinntAs'rasnbdegco,rlGreolrsm'aPnFy.C IpnltaesmmaatiloenvaellsJoauftrenralPFofOHAygiene. CalafataAn,dWEonnvigroL,nmKeunktlaelnHyeiaklZt,h R2e1i3:d2y17J,-2N2e3e.dham L. 2007. Polyfluoroalkyl chemicals in the ('UNSHpAoNpuElaSt)io2n:00d3a-t2a0f0r4omantdhecoNmaptiaorniaslonHseawlitthh aNnHd ANuNtEriStio1n99E9x-a2m0i0n0a.tiEonnvSiurrovnemeyntal DeWittH,eaSlhtahyPrearAs,peBcaidvresM,11L5o(v1e1l)e:s1s59S6,-1H6o0b2a.n D, Frame S, et al. 2009. Immunotosicity of ppreoflliufoerraotoocrt-aancotiivcataecdidreacnedptpoerrfallpuhoar.ooCcrtiatncealsuelvfoineawtse ainndtotxhiecoolloegyofp3e9(r1o)x.i76s-o9m4e. FrisbeePSr,ojBercto:okdsesJirgnA,, mMeathheordsA,,aFnldeapsarbtoircgipaPn,tAs.moElnvdirS,onFlHeetaclhtehr TP,erestpale.ct2010197(.12T)h:e1C8783-H1e8a8l2t,h Harada pKe,rfIlnuooureooKc.taMnoersiuklafwonaatAe, aYnodshpiernfalguaorTo,oScatiatnooaNt,e Kion ihzuummainsA.an2d00t5h.eiRresnpaelcicelse-asrpaencciefiocf Hines Ee,xWcrheittioen.5,SEtnavnirkoonmJ,enGtiablbsR-eFselaorucmhoy99E(,2)L2a5u3-C2,6F1.entonS. 2009. Phenotypic dichotomy fmioclel:owLinogwddeovseelsopimnednutcaeleelxepvaotseudresetroupmeslleuptoirnooacntdaninosiuclianc,iadn(dPoFvOeAr)weiinghftemianlmeidC-Dli-f1e. Houde MMo,lMeacrutlianr and Cellular J, Letcher R, Endocrinology 304:97-105. Solomon K. Muic D. 2006. Biological monitoring of KennedpyolGy,flBuuotroeanlhkyolfJfs,ubOsltsaennceGs:, OaCroenvineow.r JE,nSveiarcoantSAc,iPTeerckhinnoslR,40c(t11al).:23040643.-T34h7e3.tosicology Lau C, oAnfipteorlfelKu,orHooodceiasnCa,t.LaCiriDt,icPalfarhelveise-wHsuticnhteonxsicAo,lSogeyed34J.(42)0:0375.1-P3e8r4f.luoroalkyl acids: a LundintJ,evAileewxoafndmeorniBt,oOrlisnegnaGn,d CtohxuirccohloTg.ic2a0l09fi.ndAinmgsm.onToixuicmolPoegrifclaulorSocoicetnacneosst9c9(P2r)o:d3u6c6t-i3o9n4 MichaleakndJ,OTcrciuppaathtiioRn,alKuMlokratranliityP., GEuppitdaemPi.oSleolgvyav2e0l(6K).:92119.98. Correction for bias incoduced by truncation in pharmacokinetic 9(2):165-174. studiesofenvironmental contaminants. Environmettics Olsen G,seBruurmresliJ,miEnhavteiosnmaonf pDe,rfFlruooerholoiccthanJ,esSuelafcoantatAe,, BpuetrfelnuhoorfotheJ.xaentcasl.ul2f0o0n7a.teH,alafn-ldife of Ppeerrsfpleucotriovoecsta1n15a(t9e):i1n2r9e5t.ired fluorochemical production workers. Environmental Health Olsen G,peZroflbueolroL.oc2t0a0n7o.atAes(sPeFssOmAe)nctoonfcelnitpirda,tiheopnastiicn,falnuodrtohcyhreomiidcaplarparmoedtuecrtsiownitwhorskeerrsu.m PausienIbnatcehrnDa,tiPonaanlkAorJc,hSicvoetsot fP,OcUcnuipcaetKi.on2a00l7a.ndAEmnevtihroodnomleontgaylfoHreaelsttihm8a1t(i2n)g:2h3u1m-a24n6,exposure t(o19p5e1r-f2l0u0o3r)o.ocJtoaunroniaclaocfidTo(PiFcOoAl)o:gyAraentdroEsnpveicrtoinvmeeenxtpaolsuHreealtahssPeasrstmAent7o0(f1)a:2c8o-m5m1u.nity 23 p.25 Page 240133 Rosen M`,HuLmaaunCH,eCalotrht?onToJ.xi2c0o0l9o.giDcoaelsSEcxipeonsceusre11t1o(1P)e:r1f-l3u.oroalkyl Acids Presenat Risk to Stahlhut`eRx,peWcetledshhaolnf-sliWf.e,SsuwbasntanSt.i2a0l0n9.onBfiosopdheexnpoolsuAred,atoaribnotNhH. AEnNvEirSonsmuegngteaslt lHoenagletrhthan SteenlanPedrKs,peDcetidvdeesns11J7A(.5)2:070844.-7A89p.racticalguidetodose-responseanalysesand risk assessment SteenlanindoKc.cuJpiantCi.onMaalceNpeiidlemJi,oLlaolglyy.CE,pDiudceamtiomlaongAy,15V(i1e)i:r6a3V-7,0e.t al. 2009. PredictorsofPFOA l1e1v7e(l7s)i:n10a8c3o-m10m8u8n.ity surrounding a chemical plant. Environ Health Perspect `Tan Y-Mdi.sCploeswiteilolniIniiraHJt,aAnnddmeornskeenysM:E.A2k0i0n8e.tiTciamnaelydseips.enTdoexniccioelsoignypLeertftleurosro1o7c7t(y1l)a:c3i8ds-47 2 p26 Pa25g013e3, Tables low" Towson [. | Table 1. Median PFOA (ng/mL) in 2005-2006 (N)forcurrent and former residents. Varable |Coeane|T_eFotmeor --[Vveamsmrw|a--Cu--mno|teomer] [B|T WeatebrDiestric"t m|woaswy [ 7 T T - VNee-------- T IT3s29s0a7.m030)_ | m362i01a518) HockiTnigtle ws 61) Grow Own Vegeubles [LobMaeson 4000 [31000| 9 Ves iE J I uppers ----T--Ft-- o ---- T YNees [[ owmr sw[si s[osuee d | fe [S--i0--650[133-- s0itcomn | | cJomcomer[I ew1m-- ms | LN [Buse[36880 | [ [oWohne Whit] e| 3s26m) 9) [ [3e5s 10i5|| ---- 1 C II -- a | ECACC--T1T Gwen I[O3R38T.01G01A09T56Y2)87)[3[737565036655000)0 | [2 [22 Dsesy 1548009)[36D9606185) 1 ---- 71 |DaeFotittesoiomdons || 5070068 | |H30% ---- S731 [ [[RY Negole eorBrercisTTe|33680G2m02)1[[33666460500 ||| FTohuritdhwowmoommohnkss mithwomonds ||236807((5435859m) || 334583(5(1E4n) 1215G430 |401 (147) C "Former residents Tmited to individuals in L1 idle FlCoT cskinog amndaLnubeck wiitho>2tyseares r[esid0encae m] 20d >15 ng/mL PFOA. "SDIa31t1e0s6,of6t/e1s1t0in6g-:883/11/10065-9/30/05, 10/1/05-1 1/30/05, 12131005-1/31/06, 2/1106-3/31/06, 4/1106- 25 par Page2sor3a `Table 2. Multivariate linear regression results" (R=0.68), current residents (n=17.516"). em | oneLom Loo | ew | FROeNGfm om || CmoPrOdAa| HR VEiTrONa):GGrti referent) RY) rr -- ft11711 widens [Sex Female TT 08 [03[ous | oz| oom | o = Ea TT-- Rr eS fear T|a ms |a ow" [aom | os1 ] 30.39 40-49 [om [% one|006 [oom| Tom |ooss[00m | 02% oom | | [FoE oono 77TE7 a TeeS[| 1 Y 01S o6aw70[ooCmTre0||002m 080||TMo _oYa eCxs]| fomoking -- 4 [omen Tw [oii 5m Former WBoattieerddwsarter -- --2 1 oon 1 Tow |oo |00% | oo% | Tow oui T -- om--] "Tupper Plains [ Refewm [To Belp [ps Lite Hoc 495% T1019 [iss |066| 0001| Tis[ims| 03% 394% [iubek 7 82% [MesonCowny "T 4% | 0600 | ose [063 | 65% | i018 | tor| 0989| 211% LC Pomery | 67% [teTier | 106] 11% ""5M5o2deilndailvsioduaadljsusmtiesdsifnorg date of visit covariate data (Bottled water=505, Smoking=66). 26 p28 Pagezrof3s ima ot setoe e `Table 3. Effect of years of residence on serum PFOA by water district, with district-specific model fit. Veco0f eeWnPcReOR)|Chanpgen"Fred| | Tupp Plaine s |r35s 86| 0.18 (partial R%) explainedby 32% PFOAbyYear of 1%1 IT Mwuoen Coun D|e3285oB| 0n0C5|T0e 6s --T |_06m 1ss TLouemsd]oaiowm]] [Pomery TenJon[as Tow Tomlin] 27 p28 Page 28.0133 `Table Lubec 4. k( Multivariate n=971). linear regressio n results, former residents of Little H oc ki ng (n=602") and Variable Estimated Hall-Life | %Change in PFOA 9% Cl (year) by Year rr TT [YonBapsedd| 35 7] rere ree] 214% [165|% [ewsBYelarasopfsReesiad.en>ce[ |" or | 1 i1o6%% |[081%8||.6a1%%| [Labed---- 1 YanBlpsed 9 |85| 18% [91% 765%| Years Elapsed, 9. na' YearsofResidence - 02% [3|3 38%%| 25% [18%| 31% MFPaoirdalemleatnaeallrsyos(i0sa0du0j2ums)biyceideroldsds uxa p,0osais5ti.ivGenRogawlenfoinwnstnmogVkeigienUgcbIhaiesstl.orsymgorskantidenorgn.hs3audnmpsceiorno.snuomfinbgelbieOd Iwatwearre 28 p.30 Page 290133 `Table 5. Sensitivity analysis for half-life after various truncation cut pointsofserum PFOA. Halflife, years (95% CI" [i| ulcHocking | L1u0be3c6k7 | 5s 304-40) 1 90338 13.1) $50,110) fo 2500-33) 6.6 (58-78) BL TT veins [5964 | "Models also adjufsotrsexd, age, growing own vegetable, smoking, and consuming bod water 29 p31 Page 30.0f33 Figure Legends Fwaitgeurredis1t.rPiclto,tscuorfrennatturreaslidleongtasr,iLthOmEoSfSPrFeOgrAess(inogn./mL) by cumulative years of residence in a Ffoirgmuerre L2iat.tlPerHedoiccktiendgderecsaiydeonftsseinrudmisPcrFetOeAsecognmceennttsraotfiloenssbatsheadn 4onahnadlfg-rleiavteesretshtainma4teydeafrrsosmince. living in Liule unadjusted for Hocking (solid covariates). line: adjusted for covariates), and LOESS regression (dashed line; fFoirgmuerreL2ub.bePcrkedriecstieddendtescainydoifscsreerteumsePgFmeOnAtscoofncleenstsratthiaonn9baansdedgorenathearlft-hlainve9s eysetairsmastiendcefrloivming ifnorLcuobvaercikat(esso).lid line: adjusted for covariates). and LOESS regression (dashed line: unadjusted 30 p32 Pagetora ramerey el g rovonrum Mason Coun sore rears oy ivoning --%| = _ TET Sesctzomm 300 30007) p33 Page20133 sie. . | 2 MwalidaEs,LL oLTL.- pi B| OdRamEinLs LEie LL. .., PP CoeETC aT nRNI E ETSS, TL Tz Troma TT 165x(13030x430m00m7) p34 Pagosa Bogen' Lo fel W W Ra A he I a altee uh e . .So r of BEENRLLL I E ST L SBranEW N T G eyheTan STL a AT Wiel NSE AER ! farsa" ? z ean1350m G00 5 300071) p.35 5.36 wa0/2010 10:37 Fax Pr `PSPuttaitcuerssrserpoforstfeofipAukbuear(tPyoFsOmAro)oagnoiddPaeefeiucorottohcetMaaInde-SOnubliooaVsatiil(ePRacOSr)estos to TheC Slee Panel(TonyFietchr,Ke Scola,DedSavi) Sep302010 "JTohieslstaftpuesrrefpoorrstoseumtmaanriiczeasctdh(ePSFoOdAin,gisoofaastlateistCiBca,l2an4alpyesicsuocfrtohcetrealnatisounlsfhoipnbee.tween P(rPojFeOcSt),maenadspubreerdtiyn.thAefbllloopdosretruofmofetshechdiilndgrenwwilhlobpeasrtibcipated0in4tpheeC8eHevalethd `scientific journal. - Introduction. PJmtFbaCakssabtePieR.sOTuAhgge(esosrtmCeEdo)tfhnaidssPsoRamOedSypwoyawfsiohtrepouxabalerymtliy.cbtosmhprooeulnnsdtsso(stPhiEopCrba)oemnaevylaevlelesvaaennlimosafiltwseal Tompoedoatee ofofimrenvsaiions.Woemwthdosdewth rcoomnhseiCdFHebaothtPhreoSjeciesnucpepPlaemleFteodiweith Methods. As2im0xo0w0n,gewteheeisxyroaiucintngsewpdhadritcifhcihpfaaondrtbs3o0g7necdbooy1ms8amsdtih2to9t3i1wmgiehsoPfFtaOhllACs.FTeHnhetaylswtehfrPoorraceleetsitsfuiordvyesyuh2an0vi5hn-g smcohespeubsert5y0atnhge oefoffesoeartvsiterbonaed5opnptmh.erorsbobysr,onmdesblaoocdleel20spy.for Ccgoiiinretlrmsao)v,leolarriangthgeafsevoicgnrhgcoralefnpreoerpaotcfeohdiettnhgaspstutbeihexerypptuhyibaGaedrrntsoytcahyreiftleiddrrmeoesnnw.aiFrtrcho0hdei(PtpFfeeOrfAiseo,mdsouc)xdd.oePsSltuRsar,tOsiSwsltIeoicvcvaeoelssum,,odadeldhlioslreeesseint {hFeuOdpisNf,fW.readciv(idaeidtrheopopnulaitionaytsooffrua:ceianglpgorboeurptsyb(ertlwese)dbiyfexpocseepso1sePeEOS Reals. p.37 L 08/30/2010 10:37 FAX aoe `1T8hnemgid-/piomninLgitro.lsf. PFFoOrbAoaysn,dtPheFrOeSwsaesruamclleevserleslawteiroen2sh6iponfd2re0dnugce/dLo.didnsbooyfsh,avainndg2r0eaacnhded pbuubtenrottywPiFtOhAi.ncFroeragsiirnsg,PbFiOghSer(edxeploaysoufre19o0eidtahyesrbPeFtwOeAoontrhePhFiOgShweastsaansdsolcoiwaetsetdqwuitahr), pruebdeurcteydo1d3d0sdoayfsRlaatveirntgrheaancthheedlpouwbeesrtteyx.pTohseubriegghreosutpP,eFnOdAf.ogrroPuFpOhSa,dthaendaevletryavgaasg of ceosntsiimsaiteeadtsas1d3i8redcatiyosncaonmdpmaarginnigtthuedewiightehsotnaenpdulbolwieshsetedsxtpuodsyurwehgircohuspu.gTghsessieerdesluasyaerde pubceornttrya(satlsoamneoatshuerresdtausdyswlfhriecphorriepeodrtmeedayoaubneg)eirnpurbeelarttiyo(nmteoaPsFuOreSdeaxspborseuarsetimoatguirrlast,aionnd) girlinrelation to PFOAexposure. Conclusions. PDeFlOayAsanofdpuPbFerOtSyexhpaovsebureeeinnogbisresr.vCeaduitnitohnisipnopeueldaetdiionnicnotrerreplraetteidnwgithtehsPeFreOsSulitns,bdouys oantdhe tfhaectsathmaetbtliomod,PaFnCdmleenvaelrscahnedwpausbseerltfy-sraetpuosrbta.sFeodroenxsaemxplhe,oirtmmonaeylbeveetlhsawtegrreowdtehtecrhmainngeedss.t ``acsosmocpioautneddwsihatvhipnugbaerntyyelfefaedctoocnhaagnegaetspuibePrFtOyA..FaurntdhPeFrwOoSrkbliosopdllaenvnelesd,toraitnhveersttheimgattheese patternsofpubertybyageinrelation toexposureprior 0puberty.