Document ZBnrV6egyXydm05ZzLvgBx7bd

AR226-3386 Development of a Mammalian Screen to Evaluate Absorption and Persistence of Fluorinated Chemicals C. Finlay, G. Jevson, G. Kennedy, and J. Stadler The DuPont Company, Haskell Laboratory for Toxicology and Industrial Medicine, Newark, Delaware, USA U Abstract Questions have arisen regarding the potential of fluoroorganic cliemicals to be absorbed and to bioaccuniulate in tlte human body. Rats were used in an experiment to measure the blood uptake and clearance fora series of fluoroorganic cliemicals. Eighteen chemicals were screened at doses expected to be minimally toxic. Each ciiemical was administered by oral gavage to groups of S rats each for 10 days. Blood was collected 2 hours after the first dose, and on days 5. 10 (treatment), 13,24,52, and 94 (post-treatment). The total fluorine content (ppm F) in blood was determined by using a Wickboid torch combustkm/fluoride ion electrode analysis method. Noncompartmental analysis was conducted on blood fluorine data. The dose-normalized area under tlic blood-concentration curve (AUOD) was calculated for each chemical and used as a comparative metric. The blood AUC/D for the chemicals tested ranged from 566,500 for perfluorooctane sulfonate (PFOS) and 70,800 for perfluoroocianoic acid (PFOA) to a range o f 0 to 28,900 for ascriesofTelomer-based cliemicals. This screen could also be used to assess levels of test material derived fluorine in target orgaas or estimate tlte biological half-life of test materials. As utilized here, the screen proved valuable in assessing tile relative biopersistence of a wide range of fluorinated cliemicals. HillIntroduction The objective of tliese studies was to examine the potential of selected fluorinated organic cliemicals to be absorbed and persist in a mammalian system This rat assay was developed as a screening test that could be used to compare bioaccumulation/biopeisistence potential of the chemicals to one another. Blood samples taken fromrats at selected time points during a 10-daydosing pliase and an 84-day recovery phase were analyzed for total fluorine. The data were normalized so that comparisons could be mode, regardless of chemical characteristics or the dose administered. Non-comparttnentai kinetic analysis of tlie blood data was used to provide the basis for comparisons. Liver samples were also analyzed for total fluorine to supplenient tlie information obtained from blood analyses. IMethods - Sprague Dawley male rats Test Materials and Dosages - Selected fluorinated organic cliemicals were given to rats by gavage atlhe indicated dosages. The doses were selected to achieve minimal toxicity (some effect on body weight gain) or an upper limit o f 1000 mg/kg/day. Dosage Identifier Chemical______________________________ Img/ke/dav) A Perflurooctane sulfonate 10 B Ammonium perfluorooctouoate 20 C Fluoroalkylethyl Sulfonate 35 D Fluoroaikylethyl Betaine 75 E Fluoroalkyleduuiol Mixture 100 F Fluoroalkylethyl Carboxylate 100 G Mixture of Fluoroalkylethyl Anionic Surfactants 200 H 2-Perfluoroociyiedumol 300 I Fluoroalkylethyl Ethoxylate 300 I Fluoroalkyethyl Methacrylate Polymer 1000 K Fluoroalkylethyl Acrylate Polymer 1000 L Fluoroalkylethyl Phosphate #1 1000 M 1000 N Fluoroalkylethyl Urethane Polymer 1000 O Polyttrafluorothylne 1000 P Polytetrafluoroedtylene mixture 1000 Q Perfluojopoiyether 111 R Perfluoropolyetber #2 1000 1000 * Vehicles and Negative Controls - The test chemicals were administered as received or were suspended in water, com oil, or a mixture o f acetone and com oil (20:80). Negative control rats were dosed with wateror respective earners. Study Design MBResults Magnitude of Response Comparisons - A plot of total organic blood fluorine concentration normalized to micromotor equivalents vs. time provides a comparison of tlie magnitude of Cmax and area under tlte curve for selected chemicals, in thisexample, four selected chemicals arc sliown: __________Chemical_____ AUC1NF/D_______Cmax A 566,479.1 989.1 B 70,789.6 518.1 F 23,298.6 101.1 G 14,886.1 49.3 Comparison of AUCINF/D for Blood Organic Fluorine Across Tested Chemicals Tlie area under die curve calculation provides an estimate of total fluorine load in the rat during tlie course of the dosing and recovery periods. Fourteen of the tested 18 chemicals ore compared for relative accumulation in a mammalian system The oilier four chemicals tested liad no measurable area under the curve. Total Blood Fluorine Area Under the Curve s' I l l s Total Fluorine Analyses - Wickboid torch combustion followed by analysis with selective tonelectrode * Data analyses - All data were normalized to 0.1 nurole/kg based on dosage, percentage active ingredient, and percent fluorine, to compare kinetics from one material to another. The following parameters were calculated for the blood: AUCINF/D faren under the curve! - Represents the area under tile blood concentration curve from tlte time of initial dosing extrapolated to infinity. Cmax - Maximum observed concentration in the hlood Determination of Uptake and Clearance - A plot o f blood fluorine levels vs. time illustrates the rate of absorption and clearance from tlte blood. In this example, absorption and clearance patterns of two selected chemicals are compared. Fluorine blood levels for Chemical F do not reach steady state within the 10-day dosing period in this test No estimate of steady state level is available. Alternatively, total fluorine levels for Ciiemical E indicate that the chemical may be approacliing steady state near tlie end of tlie dosing phase. Differences in clearance patterns can also be seen initial clearance of Ciiemical F from the blood is rapid after dosing ceases and is followed by slower clearance between days 13 and die end of tie recovery piiasc. Clearance of Chemical E follows a different pattern and appears to be slower. Comparison of Organic Fluorine Levels in Blood and Liver Tlie Wickboid torch can be used for combustion and subsequent analysiso f total organic fluorine in tissue samples. In die first example, fluorine levels in blood and liver o f animals treated with Chemicals A and B arc compared at die end of dosing (Day 10), three days after the dosing pliase (Day 13) and atthe end of die recovery phase (Day 94). Both blood and liver samples have liigher levels of organic fluorine in rats treated with Chemical A than in those treated withB. - in tlie second example, two alcolwls are compared at tlie end of tlie dosing period (Day id) and at tlie end o f the recovery period (Day 94). Blood levels were similar, but levels of fluorine in the liver were higlier for one alcohol than for the other. I Discussion Normalization of data by taking into consideration die dosage administered and die organic fluorine content of the test chemical mokes it possible to readily compare different test materials. Kinetic analysis and calculation of AUCINF/D for this set of chemicals showed a wide range in die potential for fluorine to accumulate in the blood of treated rats. Area under die curve ranged from a high of approximately 566,500 for Chemical A (PFOS) to a low of zero. Fluorotclomer process chemicals had AUCINF/D values of 28,900 or less in this assay. It is recognized, however, that not all of these cliemicals had achieved steady state in the blood by die termination ofdosing on Day 10. Thus, the calculated numbers have limitations and should lie used accordingly. Todetermine if organic fluorine can be stored in odier body compartments, tissues were also combusted and analyzed by this mediod. Tlie fluorine levels in the liver indicated that blood levels do not account for the total fluorine storage in the body. A variety of liver levels were evident, indicating a need for furtiier assessment of distribution for some of these materials. Tlte Wickboid torch method of analysis is slow and tedious, but the measurement of total organic fluorine can show accumulation in tissue without having specific analytical methods available for each parent or metabolite. It is also useful when evaluating die results of exposures to mixtures, wliich make up a large portion o f this chemical selection. IConclusion This mammalian screening study was used successfully to rank a series of fluorinated chemicals for bioaccumulation/biopersistence potential. Tlie calculated blood area under the curve for perfluorooctane sulfonate (PFOS) was 8x that of ammonium perfluorooctanome (APFO) and 19-I800x that of fluoroteiomer-based materials. This screen has die potential to be a valuable too! for use in selection of chemicals for furtiier research and tn development of experimental designs. g Acknowledgements Tlie authors would like to diank the following: Study technicians - Nita Baker, Rich Mtitheno, Steve Carpenter, Charlene Smith * Fluorine analysis - Chris Bowers and Ward Gibson * Kinetic analyses - Paul HinderUter Poster Preparation - Maryanne Wilford