Document KGp4aw2REoZX2vz4QYLe9D8gK

The School of Public Health Department of Environmental Sciences and Engineering w\ THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL The University of North Carolina at Chapel Hill CB 7400. Roscnau Hall Chapel Hill. N.C 27599-7400 June 6,1995 Dr. Hasmukh C. Shah Manager, Vinyl Chloride Panel Chemical Manufacturers Association 2501 M Street, NW Washington, D.C. 20037 Dear Dr. Shah: Dr. Jim Knaak asked me to write to. you with a proposal for additional studies on vinyl chloride research that I would be interested in conducting in collaboration with the CMA. I FAXed Jim a copy of this and he will bring it to your meeting this week. I am sending you a copy by FAX and by Federal Express, so that you have a hard copy for the meeting. If you have any questions, please give me a call Thank you for your continued interest in our research. Sincerely, James A. Swenberg, D.V.M., Ph.D. Director, Curriculum in Toxicology Professor, Environmental Sciences and Engineering, and Pathology R&S151304 PROPOSED STUDIES ON VINYL CHLORIDE James A. Swenberg, D.V.M., Ph.D. University of North Carolina June 5,1995 Listed below is a series of studies on the formation and repair of DNA adducts induced by vinyl chloride (VC) that will provide molecular dosimetry information relevant to risk assessment These studies would be conducted in a manner that will complement the two generation reproductive and developmental toxicity studies currently being planned. Dose-response Studies Presently, we have data showing that preweanling rats are more susceptible than adults to VC carcinogenesis, that preweanlings develop 3-fold greater numbers of VC DNA adducts, and that preweanlings have 3-fold higher expression of CYP 2E. The adduct and carcinogenesis data are all from "high" exposures of -500 ppm. No information exists on lower exposures. By adding additional animals to the reproductive and developmental toxicity studies, we could assess the effect ofexposure concentration on the molecular dose of ethenoguanine, the primary promutagenic DNA adduct ofVC in adult and preweanling rats. Experimental design: 5 adult + 5 preweanling rats per dose (4 dosesL including controls). The projected cost is $10,000. Concentration x Time Studies No information on C x T and VC molecular dosimetry are available. Such information would assist in extrapolating risks for brief exposure from carcinogenesis data. While I do. not know what exposure concentrations will be used in the reproductive and developmental toxicity studies, several C x T groups could be constructed to examine this issue. For example, 1000 ppm x 1 hour, versus 500 ppm x 2 hours, versus 250 ppm x 4 hours, versus 100 ppm x 10 hours. Again, 5 adults and 5 preweanling rats per group would provide a reasonable number of samples. It would also be possible to compare naive versus pre-exposed rats. Project cost would be $10,000-20,000. R&S151305 Molecular Dosimetry Studies in Nonparenchvmal Cells (NPC1 versus Hepatocytes Understanding why VC targets the endothelial cell for its carcinogenic effect is critical to proper risk assessment We have preliminary data on ethenoguanine adducts in vinyl fluorideexposed rats (2500 ppm, 6 hr/day, 5 days/wk, 4 wks) that shows that the number of adducts is ~10fold higher in NPC than hepatocytes. It is of great interest to determine if important differences exist between adults and preweanling rats, and between high and low exposures. I would propose using a one week exposure to the four exposure groups investigated above under dose-response in adult and preweanling rats. DNA adducts would be measured at the end of the exposure and 3,7 and 14 days post exposure (4 doses, 2 ages, 4 times, 3 tissue/cells = 96 samples). In addition, the expression of the major DNA repair pathway, N-methylpurine-DNA glycosylase (MPG) would be examined in NPC and hepatocytes from these animals. The cost of this study would be $40,000. Studies Using [l3C^UYC When I met with the CMA Vinyl Chloride Panel, I requested that you consider having [13CJ-VC synthesized so that studies on the formation and repair of VC-induced DNA adducts could be studied relative to those adducts formed endogenously. I believe that these studies will critically inpact on any risk assessment on accidental exposures. There are many studies that could be done. First, the number of adducts formed by [13CJ-VC needs to be determined at several exposure concentrations to identify the molecular dose of induced versus endogenous adducts. I propose that closed chamber exposures to 500,250,100,50,25,10,5,2.5,1 and 0 ppm ( 5 rats, 6 hrs) be used. The cost of this portion is $35,000 and CMA supplies the [13CJ-VC. Next, I would examine the rate of repair of [13CJ-VC induced DNA adducts in a high, mid and low exposure group (3 concentrations x 5 rats x 4 times). These same animals would be housed in metabolism cages during the post exposure holding periods so that urine could be collected. The urine would be analyzed for endogenous and induced DNA adducts that had been repaired by the MPG pathway. In addition, it may be possible to identify and quantitate [13CJ-VC metabolites in the urine using NMR. Drs. Fennell and Sumner at CIIT would be possible collaborators on this. The cost of this would be $40,000. f R&S151306 HPRT Mutations in VC-exposed Mire versus VC Workers As part of our Superfund grant we are determining the HPRT mutation frequency and mutational spectra in workers in the vinyl chloride plants of France. The cohort contains over 400 workers, some of who were exposed to high concentrations of VC prior to 1974. Of these workers, some have markedly elevated numbers of mutations, while others have no increase. We are determining the molecular nature of these mutations and examining possible factors involved in differences in inter-individual variability including MPG expression and GST and CYP 2E1 genotyping. We would like to be able to compare the human data with an in vivo animal model. To this extent, we would like to have B6C3F1 mice exposed to the highest concentration of VC (500 1000 ppm) that you are using in the reproductive and developmental toxicity studies for -8 weeks. We could go with as little as 4 weeks, but feel that the longer time would increase the number of mutants available for molecular analysis. The test animal would be 3 weeks old at the beginning of exposure. A total of 48 exposed and 24 control mice would be used. The mice would be shipped to UNC in groups of 12 exposed and 6 controls at 2,4, 6 and 8 weeks post exposure, where we would isolate the HPRT mutants and conduct the molecular analyses of the type of mutations that were present We have comparable data on human cells in culture exposed to VC, chloroethylene oxide (CEO) and chloroacetaldehyde. The cost of the HPRT analyses for this experiment would be $27,000. Studies on VC-induced_DNA Adducts in Human Endothelial Cells Human endothelial cells are now commercially available. These cells could be used to compare the formation and repair of VC DNA adducts in human versus rat endothelial cells. We would expose endothelial cells to CEO or VC and determine the number of ethenoguanine, ethenocytidine and ethenoadenine DNA adducts at various times after exposure. In addition, the expression of MPG would be quantified. One reason that this experiment is important is that human angiosarcomas arising in VC workers have shown p53 mutations at AT base pairs, whereas, ethenoadenine adducts appear to be rapidly repaired in rodent liver, but ethenoguanine adducts accumulate. Therefore, we would expect that most mutations would occur at GC base pairs. By r comparing both the molecular dose of DNA adducts and the expression of MPG in human versus rodent cells, we will better understand the cause of this difference and be able to select the most appropriate biomarker for humans. The cost of this research would be $13,000. Budget The total budget for these studies is $175,000 -185,000. In addition, the CMA would need to cover the costs of animals, exposures and the synthesis of [I3CJ-VC. The studies would be conducted over a two year time frame and could begin as soon as the project is funded. The research can be provided as a gift, with no overhead, or as a grant, with 44.5% overhead. If you select the latter, I will need to submit a formal proposal once we have finalized the research program. R&S151308 R&S151309 Name of Agent Acrylamide Atdrin --------------------------1.3-Butadiene Carbamazepfne Carbon tetrachloride Chlotdane ODTt3) Ethylene dtbromkfe Formaldehyde Heptachlor Methylene chloride Progesterone 2.4.5-T.birtyl ester Trichloroethylene Vinyl chloride CAS# Leva) of Toxicological Level of Exposure Priority Slates- DART r Concern^ - - Concern r^~ 79061 High rj 309002 High 75 * 106980 Medium Medium Low Medium _ High Medium Medium cv 36507309 S' 56235 High Medium Low . Medium Medium Medium 57749 ** 50293 High High .. tow. ..........> -....... MfdltWL- Medium .High 106934 High Law Medium 50090 Low - High Medium 76448 High Low Medhim .75092 tea. Ik -- * lliiiie 57830 " .High Medium^ 93798 79016 75014 Low Medium Medium Low High Medium Low High Medium to Priority chemicals from Donald. JM, MwKsrrat, LG, Hooper, K, Book. SA and Chemoff, refwductlve/devetopmenlat toxicants for evaluation. Reprod 7ox?coJ6:90-106. 6F (1092). Prioritizing candidate (2) The evaluation of the level ol lardoatagical-concern Is based on secondary sources (databases and reviews), ft is likely that data exist which have not been considered in the evaluation. In a more detailed review, additional date may be found that will alter the assigned lava) of toxicologic conoem". Consequently, a Tow" or "medium" level of toxicologic concern should not be Interpreted to mean tfrat lhB chemical has little or no potential to cause reproductive or developmental effects. <3> Would also Include consideration of major metabolites and breakdown products such as ODE (CAS 6 72558) and ODD (CAS # 72545). (0 Progesterone Is intentionally used as a contraceptive. Unintentional exposures are believed to be I Posi-It1" brand fax transmittal memo 7671 #otpgn * t From _ 8- 4/7/85 Page f of Oept ~ Tioto Fan* [so----_ O0HCAL ROUTE EXPERIMENT LENGTH SPECIES TARGET HAST TABLE 3: CARCINOGENICITY CAJCCEK ESJOK FACKSG EEPA ORAL IUAUATKH CUU] log/tg/day)'1 (g/ts/cfey?' March 1W3 bsmv mso ORAL ^ INHALATION REFERENCE (<0/t> CU3/CTI ^ VINYL CHLORIDE ORAL: WET not DATS MT 000075-01-4 UWG uvea TUMORS tumors A t.9*0 ORAL [SLOPE] CODEIt1= UNDER REVIEW, NUMBER SUBJECT TO CHANCE. 5.4E-5 010365 IUHAUTUT4: IHIEKHITTEUT 1 TEAR RAT tlVER (BINS A 3.0E-1 R-4E-5 010967 IMHALATIOK [SLOPE] COMfENT: SEE APPEWIX A-II, ROSE COBWEfiSJONS B REASI. inhalation obit risk] canton: under review, uuhber subject to chance. GENERAL CBMEHTl THE *OST RECENTLY REVIEWED QUABI1TATIVE TOM[CITY VALUES LISTED HERE APPEAR IK ERA DOCUMENTS PHRLISflET IK 1984 AMD 19. USE Of THESE VALUES ON AH INTER1H RASIS WAS VALIDATED BT CRAVE {N4/Q5/W). THE ASEMCT IS MURE THAT THESE VALUES DO ROT INCORPORATE CONSIDERABLE INFORMATION THAT IS Ml AVAILABLE. THE OFFICE OF BEALTV AMR EWIRORHERTAL ASSESSMENT'S PQ5TTKW IS TMT THESE TOUCHY VALUES *0 NOT REFLECT STAT-OF<TE'ART SCIENCE FOR VINYL OULOMCC. T-PA SOU HRS INDIVIDUAL MIHAL BATA, HOI AVAILABLE WEEK TRE ORAL UNIT RISE WAS CALCUtATED, THAT NAT INFLUENCE THIS VALUE. ADMTIMM. INFORMATION THAT KAY RE FACTORED INTO * REVISED QUANTITATIVE TOUCHY VALUE INCUDES DATA CM INCREASED SEISlIlVin OBSERVED IN YOUNG ANIMALS AND DATA OH HEIABDLtSH/PKA&UCCKlIjEnCS. A UNIT RISC fOR AIR THAT CONSIDERS IUFORMAT 1ON OB TOMS AGE EXPOSURE INCREASES IKE RISC LOWERS THE RISC SPECIFIC 0CSE> KY XT LEAST 3-TOLD. TNE CONSIDERATION OF METABOLISM PRARMACOaRETICS VOU. FURTHER 1RCSEMSE TOE RISK. ONE tBPIMLlSHED PHtSICLOGICAU-T'IASTO PHARKAOOKIHET1C MODEL PREDICTION RESULTS IN A IOC-FOLD INCREASED RISK. ISIS, EPA* #KATES RISK UFQRMXICM HSTB* IS UPDATED tUMTlLY. FURTHER IMF OK: IRIS USER SUPPORT: <513) 569-7254