Document 65Y9ZQG8b8mbdwM0VbanzQxNo

jciui z. min juoxi i.ucuux cuini x. mxxbav *tt:ux s. loiaxEsurt. js. XOSXJtT R.TIXIHill wxanrx v. xlacx dxaavjtrsl.wI. d*ncovTci Jonr s. joxxpx xxx.XdAxxDbixT.j*. CAIIQtX c. KAJUtlS xiczaxx p. xouon XaJUIY s. xoxomox join . duxxex cannwi aximiii sit*m s. rcjixoro umci p salpwx dxsoxax xxv* nuxin c. dovoxax jajuutt xdwaxs x. xoxvxx law amcu Kmis and Hecsmjln iim it-- stxxxt. *. w. WAXxufOTOx. D.c.aooaa May 9, 1980 Docket Officer Docket H-034 Room S6212 O.S. Department of Labor 200 Constitution Avenue# N. W. Washington# D. C. 20210 nisnovt 303 49T-UOO AADiitirttiJUjr vmtxM otiicT di*& imtmzm (202) 457-1116 F/tf COPY ^NO ' -j vc Re: Docket H-034, Occupational Safety and Health Administration Request for Infor mation on Vinyl Chloride and Polyvinyl Chloride - 44 Fed. Reg. 74928# December 18# 1979; 45 Fed. Reg. 668# January 29# 1980. Dear Sir: Pursuant to Section 4 of the Administrative Procedure Act# as amended# 5 U.S.C. Section 553(c)# and the above-refer enced D.S. Department of Labor - Occupational Safety and Health Administration (OSHA) Request for Information on Vinyl Chloride and Polyvinyl Chloride and the subsequent Notice extending the time during which interested persons are invited to submit written data# views# and comments with regard to the issues described in the original Notice# The Society of the Plastics Industry# Inc. (hereinafter referred to as "SPI" and/or "The Society")# by its attorneys# hereby submits in quadruplicate certain information which is intended to be responsive to the Agency's Request. UCO 010314 I. INTRODUCTION AND SUMMARY OF INFORMATION PRESENTED SPI is a corporation organized under the Not-forProfit Corporation law of the State of New York. Its 1500 member companies and individuals and 67 operating divisions include those who supply raw materials; process or manufac ture plastics or plastics products; engineer or construct molds or similar accessory equipment for the plastics indus try; and engage in the manufacture of machinery used to make plastics products and materials of all types. SPI is the major national trade association of the plastics industry. The majority of its members are the processors and converters of the plastics resins and end products which represent 75% of the dollar volume of sales of plastics in this country; SPI's membership also represents 95% of all plastics materials and machinery manufactured in the U.S.A. The Society's concern with vinyl chloride and poly vinyl chloride begins with the manufacture of the ethylene dichloride (used to manufacture the monomer) and the manufac ture of vinyl chloride monomer (VCM), carries forth through its polymerization into polyvinyl chloride (PVC), continues with the various processes which convert the PVC resin into its multitude of end uses, and includes, ultimately, the re cycling or disposal of PVC products. In the United States there are 17 ethylene dichloride plants, 13 plants which produce vinyl chloride monomer and 42 polymerization plants. ucc 010315 Twenty-two companies representing over 95% of the domestic VCM and PVC capacity are active members of SPl's PVC Safety Group. SPl's PVC Safety Group has prepared the information, data and views contained in what follows, and it is presented in a form which corresponds in large part to the explicit re quests for information contained in the Agency's Notice. In summary, The Society's responses to the questions asked are as follows: 1. OSHA is aware of the studies on vinyl chloride sponsored by Imperial Chemicals Industries, Limited; Montedison; Rhone-Poulenc Industries; and Solvay et Cie. in Or. Maltoni's laboratory in Bologna, Italy. These most recent data of Maltoni indicate pos sible effects in rats exposed to 10 ppm of vinyl chloride but no increase in tumors was found in experimental rats exposed below 10 ppm. It is clearly evident that rodents are more suscepti ble than humans and that human experience should be given higher importance than animal studies. Animal data have predicted an angiosarcoma in cidence rate over 500 times higher than that observed in man. 2. It has been reported in the literature that VCM can exert a carcinogenic effect transplacentally; -3- ucc 010316 3however, this phenomenon has only been demon strated in pregnant rats exposed to very high concentrations. Additional work in this area needs to be done using lower, more realistic doses since available data indicate that the rates of metabolism in the rat shift as exposure concentrations of vinyl chloride change. Vinyl chloride did not cause significant embryonal or fetal toxicity and was not teratogenic in stud ies in rats, mice or rabbits. We know of no valid scientific paper associating vinyl chlor ide with human birth defects at any level of exposure. 3. While no carcinogenic effect of inhaled PVC has been demonstrated in animals or man, recent data indicate that like most nuisance dusts slight effects may occur in the lungs following exposure to high concentrations of the dust. 4. Although there are no new epidemiological data on health effects associated with vinyl chloride exposure which would appear to change the conclu sions from those considered in the current stan dard, The Society has contracted for a complete, independent analysis of all available, relevant epidemiologic data. This is particularly im portant since it is not always made clear in subsequent papers reviewing them that many of -4- ucc 010317 the studies which have been reported represent repeated investigations of the same population or subsets thereof. Considering the magnitude of this project, it will not be finished by the May 9, 1980 deadline associated with the Request but these materials will be submitted to the Agency when they have been completed. 5. The Society is not aware of any new, unpublished case reports on cancer associated with vinyl chloride or polyvinyl chloride but is submitting to the Agency the most recent, world-wide com pilation of all liver angiosarcoma cases asso ciated with VCM. 6. It has been demonstrated that if mutagenic ef fects occur as monitored by chromosomal analysis of circulating lymphocytes, they were the re sults of high exposures; the changes have not been permanent since they have been reversible. The changes did not occur at lower levels of exposure. The clinical significance of the re versible changes is not known. 7. Being a poorly soluble gas, vinyl chloride does not accumulate from chronic exposure, but, rather, is rapidly exhaled after exposure ceases. Hence, there can be no body burden in the usual meaning of the term. 3- ucc 010318 8 and 9. 10. 11. An overview of PVC manufacturing operations, types of resin, residual monomer levels, and PVC dust experience is presented with infor mation on monitoring results, control technology and personal protective devices. Variability in resin type and the resin type relationship to differing residual monomer content in the resin, varying VCM exposure potential from both resin and dust, and the type of PVC dust and other conditions which might be expected in both the polymerization and fabricating indus tries are explained. SPI is unaware of any change in the types of occupations, jobs and industries which present a potential for exposure to VCM or PVC. The Society has no data on the numbers or break down by sex of employees exposed. The VCM/PVC industry is engaging in the use of appropriate engineering controls, work prac tices and personal protective equipment and is trying to stay in compliance with the existing standard; the industry knows of no additional, feasible measures to reduce exposure below the present level. PVC dust is adequately regulated by OSHA's nuisance dust permissible exposure level (29 C.F.R. S1910-100Q) and has not been shown to be hazardous at that level of exposure. -b- ucc 010319 II. SPECIFIC INDUSTRY RESPONSES TO INFORMATION REQUESTED (1) Experimental Test Results for Carcin ogenicity of Vinyl Chloride At Atmos pheric Exposures Less Than 50 pom The current studies on vinyl chloride are those con ducted in Or. Maltoni's laboratory in Bologna, Italy. As OSHA is aware, these investigations are sponsored by Imperial Chemicals Industries, Limited; Montedison; Rhone-Poulenc In dustries; and Solvay et Cie. These most recent data of Maltoni indicate probable effects in rats exposed to 10 ppm of vinyl chloride but no increase in tumors was found in experimental rats exposed be low 10 ppm. As to the mammary tumors Maltoni noted at lower levels, the data are not convincing because the experimental animals used are known to have a high incidence of spontane ous mammary tumors. As will be discussed below rodents are more susceptible than humans and human experience should be given higher importance than animal studies. Or. Maltoni's data were reported in detail at a re cent OSHA/NIOSH/NIEHS sponsored Symposium, March 20 and 21, 1930 in Bethesda, Maryland. An unedited stenographic tran script of the entire Symposium and photographic copies of most of the slides are attached as Appendix A. In Maltoni's studies, rats, mice and/or hamsters were exposed to concentrations ranging from 30,000 ppm to -7- ucc 010320 1 pom. The attached summary statement by the Suropean spon sors quotes Dr. Maltoni and indicates that extensive statis tical evaulations of Dr. Maltoni's data nave been completed. Appendix B. In that summary. Dr. Maltoni summarized his animal studies as follows: ...the following tumours should be given proper attention viz, extra-hepatic angiosarcomas, hepa tomas, Zymbal gland carcinomas, liver angiosar comas, neuroblastomas, nephroblastomas, fore stomach papillomas and mammary carcinomas. In oncological terms, the meaning of the results at the lowest doses may be better evaluated by considering, not separately, but together, the tumours found to be VCn dependent. Thus the fol lowing results should be considered: - at 25 ppm - In 120 animals, 5 liver angiosarcomas, 4 Zymbal gland carcinomas and 1 nephro blastoma. at 10 ppm - In 120 animals, 1 liver angiosarcoma, 2 extra-hepatic angiosarcomas and 2 Zymbal gland carcinomas. at lmg/kg - In 150 animals, 3 liver angiosarcomas, 1 extra-hepatic angiosarcoma, 1 hepatoma and 5 Zymbal gland carcinomas.... These data add to that previously published by Dr. Maltoni since tumors occurred in rats exposed to 25 or 10 ppm of vinyl chloride gas. Maltoni's Suropean sponsors state. In addition, it is worthwhile emphasising that none of the previously cited tumours have been observed at 5 ppm by inhalation and 0.03 mg/kg by ingestion. These data will be published as part of the proceed ings of Club de Cancerogenese Chemique held at the Curie -3- ucc 010321 Foundation in Paris, France, November 10, 1979. These pro ceedings, which will be supplied to OSHA as soon as available, will contain an even more complete report of Maltoni's stud ies than was presented in Bethesda on March 20, 1980. In regard to the response of laboratory animals to vinyl chloride gas, the attached paper by Gehring, Watanabe and Park is extremely pertinent. Appendix C. This paper indicates the necessity of considering the rate of metabolism and body size of different species when comparing the response of different species to vinyl chloride. Many factors, such as those considered by Gehring, Watanabe and Park, no doubt are involved in the wide differ ence between the high incidence of angiosarcoma in small ro dents and the much lower incidence in man. It is clearly evident that rodents are more suscepti ble than humans and that human experience should be given higher importance than animal studies. Dr. David Rail, Direc tor of NIEHS, has commented on the wide difference between the susceptibility of man and rodents. Appendicies D and E. He stated that in regard to angiosarcoma the available data ...project a cancer incidence rate 300 times higher than has so far been reported in man by epidemiological studies for vinyl chloride. (Rail, 1977, Appendix D, p. 2.) -9- UCC 010322 (2) Studies of Transplacental Carcinogenic and Teratogenic Effects in Humans or Animals at Any Level of Exposure to Vinvl Chloride It has been reported that VCM can exert a carcino genic effect transplacentally-^--however, the phenomenon has only been demonstrated in pregnant rats exposed to very high (10,000 or 6,000 ppm) concentrations of the material. Additional work needs to be done using lower, realistic doses since available data indicate that rates of metabolism in rats shift as exposure concentrations of vinyl chloride change and that some mechanisms of metabolism are saturable.-^ Vinyl chloride did not cause significant embryonal or fetal toxicity and was not teratogenic in studies in rats, mice or rabbits^ even at levels which resulted in maternal toxi city. we know of no valid scientific paper associating vinyl 1/ Maltoni, C., Vinyl Chloride Carcinogenecity: An Experi mental Model for Carcinogenesis Studies. In "Origins of Human Cancer. Book A; Incidence of Cancer in Humans." H.H. Hiatt, J.D. Watson and J.A. winsten. Cold Spring Harbor, Cold Spring University, 1977. 2/ Maltoni, C., Carcinogenicity Bioassays of Vinyl Chloride Monomer: A Model of Risk Assessment on Experimental Basis. Symposium Paper No. 1 (1980). 3/ Watanabe, P.G. and Gehring, P.J., Dose Dependent Fate " of Vinyl Chloride and Its Possible Relationship to Oco- genicity In Rats. Environmental Health Perspectives 17:145-152 (1976). 4/ John, J.A., Smith, F.A., Leong, B.K.J., and Schwetz, B.A., The Effects of Maternally Inhaled Vinyl Chloride on Em bryonal and Fetal Development in Mice, Rats, and Rabbits. Toxicol, and Appl. Pharmacol. 39:497-513 (1977). 10 - ucc 010323 chloride with human birth defects at any level of exposure. 1. TRANSPLACENTAL CARCINOGENESIS Maltoni has reported that exposure of female rats to 10,000 and 6,000 ppm of vinyl chloride has resulted in transplacental effects in their offspring. No data have been found in which pregnant animals have been exposed to lower concentrations. Rice^/, although not having actually studied vinyl chloride in his laboratory, reviewed the sub ject of transplacental carcinogenesis, in discussing the above-mentioned work of Maltoni, Rice refers to the important role of biotransformation of VC to the probable carcinogenic metabolite. This metabolic transformation in the pregnant female/ the possibility of a similar transformation in the fetus, the kinetics of placental transfer (which processes can be bidirectional), and the metabolic degradation in both the gravid female and the fetus all illustrate the complexity of transplacental carcinogenesis. Rice also rightly points out that in the case of vcm the probable carcinogenic metabolite has a relatively short half-life. This would limit the times for transfer across the placenta to the fetus and for distribution to the fetus. Although the data of Maltoni indicate that the metabolite either crosses the placental barrier or is formed in the fe tus in sufficient concentration to elicit a carcinogenic 5/ Rice, J., Transplacental Carcinogenic Effects. Sympo" 3ium Paper No. 27 (1980). ucc 010324 response, the short half-life suggests that the effect would be minimized at lower levels of maternal exposure. Unfortu nately, sufficient data are lacking on much of the foregoing, and, therefore, definitive conclusions cannot be reached. Another complicating factor, even over and above those usually recognized in extrapolating from Maltoni's transplacental carcinogenic data to rats to a possible hu man situation, is the knowledge that rats are far more sen sitive to VCM than humans. (See response to Request no. 1.) In addition, there are marked differences in placental struc ture between humans and rodents. The following discussion of the possible effects of these differences in placentation with regard to teratogenesis is equally germane to the consideration of transplacental car cinogenesis: ...Both man and the test animals commonly used pos sess chorioallantoic placentae, but that of man is the hemochorial one consisting essentially of fetal villi hanging in a pool of maternal blood. The chorioallantoic placenta of rodents and lagomorphs (rabbits) is the complex hemoendothelial type which consists of closely juxtaposed and highly modified fetal and maternal cells, permeated by a labyrinth of blood sinuses. An even more significant differ ence between the two types is that man has only the chorioallantoic placenta, whereas the rodents and the lagomorphs have a yolk-sac placenta as well. In man, once the chorioallantoic placenta has formed, most if not all, drugs reach the fetus by this route. In the rodents, often used as test animals, the pre sence of two types of placentae in the same animal means that the drugs might reach the embryo in two different ways, and it seems probable that in the earliest most vulnerable stage, the drugs that enter _ - ) _ ucc 010325 the embryo do so predominantly via the yolk-sac placentae/.... The marked difference in the structure of the pla centa between rats and humans, the alteration in metabolism at lower dosages, and the recognized higher susceptibility of the rat to angiosarcoma must all be taken into account in interpreting Maltoni's results at extremely high concen trations. The highly idealized scheme (Figure 1) may serve to highlight some of the complexities of these factors. 2. TERATOGENIC EFFECTS The landmark study of the teratogenic potential of VCM remains the industry-supported study of three species by John et al., first reported in part at the 14th Annual Meeting of the Society of Toxicology in 1975. John and her co-workers subsequently published a detailed report of the v,wor k and again reiterated the findings at this most recent Symposium. The authors' published summary of this important study is as follows: ...Groups of pregnant CF-1 mice, Sprague-Dawley rats and New Zealand white rabbits were exposed to 500 ppm of vinyl chloride 7 hr. daily during the period of major organogenesis. Subsequently, other groups of mice were similarly exposed to 50 ppm of vinyl 6/ "The Testing of Chemicals for Carcinogenicity, Mutageni city and Teratogenicity," Minister of Health and Welfare, Canada, 1973. 7/ John, J.A., Smith, F.A., Leong, B.K.J. and Schwetz, 3.A., " The Effects of Maternally Inhaled Vinyl Chloride on Em bryonal and Fetal Development in Mice, Rats, and Rabbits. Toxicol, and Appl. Pharmacol. 39:497-513 (1977). 13 ucc 010326 EXOGENOUS CHEMICAL LEGEND CHEMICAL, - -- - TOXIC (CARCINOGENIC) METABOLITE ---------NON-TOXIC (NON-CARCINOGENICI METABOLITE FIGURE 1. HIGHLY CONCEPTUALIZED SCHEME OF THE PATHWAYS FROM MATERNAEXPOSURE TO A CHEMICAL TO THE EXPOSURE OF FETAL TARGET ORGANS. THE INFLUENCE OF THE PHYSICOCHEMICAL PROPERTIES OF THE SPECIFIC CHEMICAL, AS WELL AS MANY BIOLOGICAL CAPABILITIES OF THE ORGANISM. ON THESE PATHWAYS ARE NOT CONSIDERED IN THE DRAWING. - 14 - UGC 010327 chloride and rats and rabbits were exposed to 2500 ppm of vinyl chloride, while maternal toxicity was observed, vinvl choride alone did not cause signi ficant embryonal or fetal toxicity and was not tera togenic in any of the species at the concentrations tested. Maternal toxicity was more prominent among mice than among rats and rabbits. Simultaneous ex posure of some of the pregnant animals to vinyl chloride by inhalation plus 15 percent ethanol in the drinking water resulted in toxic effects greater than those associated with exposure to vinyl chloride alone in the three species. The maternal toxicity was enhanced to an extent greater than the embryotoxicity. (Emphasis added.) It should be noted that, to our knowledge, the con clusions reached by John et al. with regard to the terato genic potential of VCM have not been seriously questioned and, in fact, have been confirmed. Dr. John, in her presentation at the Symposium, dis cussed briefly the results of two additional studies of the teratogenic potential of VCM which have appeared in the re cent literature. The first was a report of work carried out in Hungary,^ the findings of which were consistent with those reported by John et al. The second report, origina ting with the institute of Hygiene and Occupational Health in Bulgaria, is still available only in abstract form. Al though sufficient detail is not presented in the abstract to permit a critical evaluation of the study, the report al leges a teratogenic response at much lower levels of VCM exposure than those shown to have no effect by either (Jngvary 3/ (Jngvary, G., The Teratogenic Effect of Vinyl Chloride. MUNKAVEDSLEM (Work Safety) 25:29-33 (1979). ID - ucc 010328 or John et al. A complete assessment of this Bulgarian study is essential before it can be given any credence. Dr. John also mentioned the Symposium presentation of Hehir-/. As far as can be determined from the transcrip tion of Dr. Hehir's talk, as well as what can be gleaned from a prepublication copy of the CPSC report-^/, the study did not address teratogenesis. All FQ animals were exposed before mating but progeny were not. Thus, although effects on reproductive capacity or genetic changes in the germ cells (e.g., dominant lethal effects) could possibly be manifest, true teratogenic events dependent upon exposure of the fetus could not be revealed. It should be noted, however, that the Fq exposure did not result in any alterations in the various parameters monitored in the F^, ad ^3 genera tions. In summary, the most completely documented study of the teratogenic potential of VCM, viz.. the study of John et al., reveals that under the high exposure conditions of that study inhalation of VCM by pregnant rats, mice or rab bits was neither embryo nor fetotoxic, nor was it teratogenic 9/ Hehir, R., Cancer Induction Following Single and Multiple ~ Exposures to a Constant Amount of Vinyl Chloride Monomer. Symposium Paper Ho. S (1980). 10/ Hehir, R.M., 3ierbower, G., Willigan, D.A., Kolaja, G., Marts, G.S., Hinton, D.E., Dimmick, R.L. and Wiles, J.S., Toxicology, Carcinogeniity and Reproductive Effects of Single and Multiple Exposures to Vinyl Chloride in Rats and Mice. CPSC Prepublication Release, April 1, 1979. - iO - ucc 010329 even at concentrations sufficient to cause maternal toxicity. While an additional published report basically confirms the latter conclusions, results available only in abstract form from the Bulgarian literature purport to reveal a teratogenic effect for VCM at lower levels. Although this latter infor mation is contradictory of the study by John and her coworkers, as well as that of the Hungarian study, its full significance must await evaluation of the complete report when it becomes available. Further, it should be noted that the maximum dose levels tested in the study of John et al., 2500 ppm in rats and rabbits and 500 ppm in mice, provide ample margin for safety extrapolation from these test species to the human situation. Finally, to our knowledge, there are no reports which clearly relate birth defects in humans to maternal, or for that matter, paternal exposure to VCM. Two relevant studies which have been published^/^^ indicate no relationship be tween population exposure to VCM in the area surrounding PVC formulation plants and birth defects. Infante et al.^ 11/ Edmonds, L.D., Anderson, C.D., Flynt, J.W. Jr., and Heath, C.W. Jr., Congenital Cental Nervous System Mal formations, Kanawah County, west Virginia. O.S. Public Health Service, CDC, Atlanta, EPA-76-60-2 (1976). 12/ Edmonds, L.D., Falk, H. and Nissim, J.E., Congenital Malformations and Vinyl Chloride. Lancet ,ii:lQ98 (1975). 13/ Infante, P., Wagoner, J.K., McMichael, A.J., Waxweiler, R.J. and Falk, H., Genetic Risks of Vinyl Chloride. Lancet 11:734-35 (1976). - 17 - ucc 010330 have suggested a causal relationship between paternal expo sure to VCM in the industrial setting and pregnancy outcome. The adequacy of the data supplied by Infante et al. was al most immediately questioned-^/. More recently, Haas and Schottenfeld^/ have leveled severe criticisms at the infante study, and the following is extracted from their paper: ...Analysis of questionnaire responses suggested that the number of fetal deaths per 100 conceptions was higher in the VCM-exposed group than in the comparison group. This difference was reported only for the period following vinyl chloride exposure. Adjustments removing women who were chronic aborters eliminated statistically significant differences^! While the authors felt that these observations were likely to reflect a real difference in pregnancy outcome not attributable to either interviewer or patient recall bias, the conclusions were based on indirect sources of information and could not take into account the multiplicity of maternal factorsknown to affect pregnancy outcome. The study design precluded documenting in even the crudest manner the validity of pregnancy historieTT Withoutsuch adjustments and validation, the inferences made can not be sustained and little light is shed on the possible association of abnormalpregnancy outcome with paternal occupational exposure to VCM. (Em phasis added.) Likewise, others have raised serious doubts regarding the validity of the conclusions drawn by the authors of the Infante et al. study. For example. Downs et al.^ so com- 14/ Paddle, G.M., Genetic Risks of Vinyl Chloride Lancet 1:1079 (1976). Appendix F. 15/ Haas, J.F. and Scbottenfeld, D., Risks to the Offspring from Parental Occupational Exposures. J. Occup. Med. 21:607-13 (1979). Appendix G. 16/ Downs, T.D., Stallones, R.A., Frankowski, R.F. and Labarthe, D.R., Vinyl Chloride, Hirth Defects, and Fe tal Wastage: A Critical Review. Private Communica tion. Appendix H. 13 - ucc 010331 pletely discredited the study that their ultimate conclusion was as follows: ...It does not seem possible to salvage anything from this study.... Among the more specific criticisms are the following: The authors gave no information on the distribution of workers' reported recall of time intervals since pregnaneies. Such information would be useful in assessing the validity of this study, since it is well known that the reliability of recall of oast events decreases with time elapsed since the events. The authors' analytical methods are invalid since the T. . test requires that the two rates being com pared be independent, and this is not the case.... ..The methods used by the authors to test signifi cance are inappropriate since pregnancies are clustered.... ...The misleading conclusions drawn by the authors were brought about through the selection and use of their control group" ...The purpose of adjusting rates is to make them comparable. Adjusting a rate r to a population A and another rate to a population B, and then com paring the adjusted rates r and s is contrary to the purpose of adjusting rates, and the resulting comparison does not make any sense. But this is precisely what the authors do when they adjust the prior exposed rate to the prior control group, then adjust the subsequent exposed rate to the subsequent control group, and then compare the adjusted rates. When adjusted rates are to be compared the rates should be adjusted to the same population. ...The comparisons of rates made by the authors are irrelevant to the hypotheses tested oy them and to' their corresponding conclusions. (Emphasis aUcTedT) - 19 - ucc 010332 Similarly, McMahon--^ opens his review of the Infante paper with the following comment: ...It is disappointing to see an article of such poor quality as this published in the Lancet. The data are subject to serious criticism on several counts. and, after detailed point-by-point analysis of the study, presents the following conclusory statement: In short, this paper deserves ...no consideration whatsoever in weighing the question of whether there is or is not a genetic risk associated with exposure to VCM. (Emphasis added.) The foregoing reviews, two of which were available in 1977, completely rebut the scientific validity of the paper by Infante et al. in this matter. Absent a scienti fically sound defense of this paper by the authors or their scientific peers, continued citation of this paper is in appropriate. 17/ MacMahon, B. (Professor of Epidemiology, Harvard School of Public Health) Vinyl Chloride and Human Reproduction. Private Communication, 1977. Appendix I. - 20 - ucc 010333 (3) Experimental Studies of Carcinogenicity and Other Toxic Manifestations For Any Level of Polyvinyl Chloride Exposure. These Effects Should Include, But Are Not Limited to, Mutagenicity, Teratogeni city, Embryo Toxicity, and Other Trans placental Effects As well As Cytotoxic and Cytogenic Effects on Sperm Cells. To the Greatest Extent Possible, Complete Information Concerning the Industrial Source of the Polyvinyl Chloride, the Size and Characteristics of the Particles, and Exposure Levels or Concentrations of PVC and Residual VC Should Be Included for Each Study while no carcinogenic or other toxic effect of inhaled PVC has been demonstrated in animals or man, recent data in dicate that, like most nuisance dusts, slight effects may occur in the lungs following high exposures to PVC dust.^^ Two reports on PVC dust were presented during the 18/ The American Conference of Governmental Industrial Hy gienists in the preface to the 1979 List of Threshold Limit Values for Chemical Substances in the Work Air makes the following statement concerning nuisance par ticles: Nuisance particulates. In contrast to fibrogenic dusts which cause scar tissue to be formed in lungs when inhaled in excessive amounts, so-called 'nuisance* dusts have a long history of little adverse effect on lungs and do not produce significant organ ic disease or toxic effect when exposures are kept under reasonable control. The nui sance dusts have been called (biologically) "inert" dusts, but the latter term is inappro priate to the extent that there is no dust which does not evoke some cellular response in the lung when inhaled in sufficient amount. However, the lung-tissue reaction caused by inhalation of nuisance dusts has the following characteristics: (1) The architecture of the air spaces remains intact. (2) Collagen (scar tissue) is not formed to a significant extent. (3) The tissue reaction is potentially reversi ble. _a - ucc 010334 course of the Symposium, that is, the papers by Groth and Wagner. The paper by Frongia, et. al., cited as reference no. 3 in the December 18, 1979 Notice, is one of many pub lications which deal with experimental exposure of test animals to vinyl chloride. In addition, SPI is aware of feeding studies conducted either with polyvinyl chloride resin, polyvinyl chloride copolymer resins, or low molecular weight fractions extracted from commercial PVC resins and/or copolymers. Two of these reports, one done at Harvard and one by Smith et al., are attached as Appendices J and K. Other reports are in the files of the Food and Drug Adminisration (FDA) and efforts are being made to obtain copies. As soon as they have been released to us, copies will be sent to the Docket Officer. With regard to the papers presented by both Groth and Wagner, the specific nature and particle sizes of the samples used are not completely clear. It is essential that when written versions of their papers become available for study, these deficiencies be eliminated. For the present, we can only assume that fine particles (dispersion resins) were used. As noted by Wagner, these may contain surfactants or other suspending agents. Hence, their use may result in effects which were misattributed. As stated by Dr. Wagner, he has not been able to reproduce the positive results of his early work despite repeated attempts. Nevertheless, taking the reports at face value, both studies appear to be consistent in demonstrating that exposure 22 - ucc 010335 of experimental animals to respirable PVC dust results only in a low level of toxic response and in the retention of dust particles in the lungs with the development of macro phage aggregates, a normal clearance mechanism used by the lung. It is significant to note that these experimental exposures (at least in the work of Groth with monkeys) did not result in impairment of pulmonary function. Although both authors considered that the dust induced a low-level pneumoconiosis^/ in the exposed animals, their reports did not indicate the presence of fibrotic tissue which is ob served in acute pneumoconiosis resulting from exposure to other substances such as silica. The observations of Groth and Wagner appear to be quite consistent with the experimental work and observations reported by Frongia and his co-workers. Thus, it appears that in the experimental animals studied, exposure to re spirable PVC dust particles results in retention of such dust particles for long periods of time, perhaps for the entire lifetime, and the development of macrophagic responses to these particles. A major deficiency in all these studies is the ab- 19/ Pneumoconiosis, which literally means dust in the lung, can range from benign effects such as mere storage of particles in the lung to very severe effects such as fibrotic changes and death. It must be emphasized that as used in this response and by the speakers at the March 20-21 Symposium only lung storage and very minimal tis sue response were seen. Fibrotic changes were not ob served. - 23 - UCC 010336 sence of a control using another inert "nuisance" dust. Thus, the observations made as a result of exposure to PVC dust may be a characteristic response of many dusts rather than a phenomenon unique to PVC. As to the ingestion studies undertaken for the purpose of assuring the safety of PVC packaging materials, feed ing either the whole resin or the low molecular weight (ex tractable) fractions showed no observed chronic effects up to the maximum quantities used, i,.e. in the range of 5%-10% of the animals' diets. In this connection, one other study should be mentioned, _i.e., that conducted by CIVO/TNO in Holland, a copy of which is attached as Appendix L. it is mentioned here only because a porous PVC powder was incor porated into the animals' diets as the vehicle to carry vinyl chloride monomer in a feeding study intended to measure the carcinogenic response of rats to vinyl chloride monomer. In that study, while it was not one directed at PVC, there was no observed effect attributed to exposure to PVC. Summarizing, except for the feeding studies utili zing PVC and its copolymers, studies which showed no toxic effect attributable to PVC, and those studies discussed above, SPI is not aware of other experimental studies dealing with the toxicity of PVC. Perhaps comment should be made on the speculative remarks made at the Bethesda Symposium concerning the impact of PVC dust on occupational exposure to vinyl chloride. - 24 - ucc 010337 The hypothesis is that the dust is carried into the lung and thereby distributed throughout the body. Even were the hypothesis correct/ and we think it is not, the quantity of monomer currently contained in PVC is so small that it would make this speculative exposure of no practical signi ficance. _ l>o - ucc 010338 (4) Epidemiologic Studies of Either Vinyl Chloride or of Polyvinyl Chloride (i.e., cohort/ cross-sectional/ or case-control) Because of the importance of this area of informa tion, The Society postponed preparing responsive commentary until the recent Conference to Reevaluate the Toxicity of Vinyl Chloride, Polyvinyl Chloride and Structural Analogs had been held. Prior to this Symposium it had been specu lated that, perhaps, some new epidemiologic data or infor mation might be presented concurrently with the industrysponsored presentation of Or. w. Clark Cooper. This, of course, did not happen. In fact, it is The Society's view that nothing new in this area was presented at all. However, because of the Agency's interest in the subject area, SPI concluded that a detailed review of the existing epidemiology would be in order and appropriate for filing with this OSHA Docket in response to the request for this information. Accordingly, The Society has contracted for a complete, independent analysis of all the relevant epidemiologic data. Considering the magnitude of this pro ject, it is obvious that it will not be finished by the May 9, 1980 deadline associated with the Request; hence these materials will be submitted when completed. It should be pointed out that, as is apparent from papers presented at the Bethesda Symposium, a factor complicating the preparation of this analysis involves the fact that it is not always - 26 VJCC 010339 made clear in subsequent papers reviewing them that many of the studies which have been reported represent repeated investigations of the same population or subsets thereof. - 27 - ucc 010340 (5) Case Reports and Case Series of Brain, Lympho-hematopoietic, Lung, and Liver Cancers By Facility and Relevant Demo graphic Variables, Such As Age, Sex, Race, Date of Diagnosis, Date of Death, Date of First Exposure, and Length of Exposure For Either Vinyl Chloride or Rolvvinvl Chloride At present, The Society is unaware of any informa tion responsive to request #5 which is not already contained in the published literature. However, since the papers prepared by Dr. John Staf ford of Imperial Chemical Industries, Ltd. were not consid ered appropriate for presentation at the above-referenced Symposium, it has occurred to SPI that the Agency might care now to have a copy of the most recent compilation of data on the world-wide incidence of angiosarcoma of the liver. Dr. Stafford's tables, copies of which have already been supplied (and, indeed, have been supplied on an ongoing ba sis) to the Director of the National Institute for Occupa tional Safety and Health, are a complete compilation of all liver angiosarcoma deaths due to exposure to vinyl chloride monomer through January, 1980. Appendix M. As can be seen from a review of these data, there have been only 42 cases of liver angiosarcoma reported in the last five years and a total of 84 cases reported to date. For background information on how Dr. Stafford came to be interested ih keeping a register of the liver angio sarcoma cases refer to the attached correspondence between Dr. Stafford and Dr. Robbins of NIOSH. Appendix. N. - 23 - ucc 010341 (6) Mutagenicity Study Results of Vinyl Chloride or Polyvinyl Chloride As Measured By Analysis of Human Body Fluids, e.g., Direct Mutagenic Testing With Peripheral Blood Lymphocytes, NonDisjunction In Humans With JTFF Sperm Test And In Vivo Cytogenetics It has been demonstrated that if mutagenic effects occur, as measured by circulating lymphocytes, they were the results of high exposures; the measured effects have not been permanent changes since they were reversible. The effects did not occur at lower levels of exposure. The clini cal significance is not known. The attached report by Hansteen, Hillestad, Thiis- Evensen and Heldaas is extremely important. Appendix 0. The mean chromosome-breakage frequency, which was signifi cantly higher than controls when analyzed in 39 workers in 1974, was found on subsequent reexamination 2-2.5 years later to be no higher than the controls. Hence, whatever "effects" may have been measured or whether they were related to high exposure to vinyl chloride or not, the "effects" reverted to normal when exposures to vinyl chloride (and possibly other materials) were reduced. It is our understanding that similar results on a similar study are being prepared for publication by ICI in England and that they will supply a copy of the manuscript when it is available. Picciano et al. found no effect in a study of men producing vinyl chloride monomer and those workers probably had lower levels of exposure than those above. Appendix ?. - 29 - ucc 010342 They summarized their data as follows: This report presents cytogenetic findings from a group of 209 workers employed for up to 28 years in the manufacture of vinyl chloride monomer at the Texas Division of Dow Chemical U.S.A. Cytogenetic evaluation results from this group were compared to results found in examination of individuals being considered for employment. Statistical analyses were performed on a group basis for chromatid aber rations, chromosome aberrations and proportion of abnormal cells; no statistical difference of significance was found between the two groups. Comparison of these results with reported studies suggests that the level of cytogenetic aberrations in vinyl chloride workers is pro bably related to the length and level of expo sure, and that risk of adverse genetic effect can be avoided in controlled, minimal-exposure environments. Fabricant attempted to summarize the mutagenic stud ies on vinyl chloride at the Symposium. This report merely reviewed the collected, previously-published information; nothing new was presented. The Fabricant report pointed out that in the O.S. genetic anomalies resulting in infant mortality increased from 54 in 1915 to 15% in 1965. She alleged that 33% of pediatric hospital admissions are due to genetic defects and that 80% of all clinical mental retardation in the CJ.S. arises from genetic causes. She speculates that these ob servations are due to "an environmental component" creating birth defects. No mention is made of higher incidence as a result of the use of improved diagnostic tools or longer survivership of affected infants. This author also relied on the discredited paper - 30 - ucc 010343 by Infante et al. This publication (reference 12 in the December 13 Notice in the Federal Register) alleging repro ductive effects in wives as a result of mutagenic changes in husbands who were exposed to vinyl chloride has been dis credited because of faulty methodology. See Appendicies G, H, and I. The faulty nature of this study has been re peatedly called to OSHA's attention and/ therefore/ absent a sound scientific defense of this study by the authors or their scientific peers/ Fabricant should not have cited it. - 31 - ucc 010344 (7) Body Burden Measurments of Vinyl Chloride In Humans The meaning of this specific request for information is not clear. Being a poorly soluble gas, vinyl chloride does not accumulate from chronic exposure but, rather, is rapidly exhaled after exposure ceases. Hence, there can be no body burden of vinyl chloride as the term is usually applied to the accumulation of heavy metals, large organic compounds or radio nuclides. Baretta, Stewart and Mutchler studied this subject and reported on "Monitoring Exposures to Vinyl Chloride Va por: Breath Analysis and Continuous Air Sampling." American Industrial Hygiene Association Journal. Vol. 30, NovemberOecember 1969. The data in this study clearly shows a rapid decay in the expired air in industrially exposed employees and laboratory subjects when exposure to VCM ceases. Published metabolic studies on laboratory animals-^' and human subjects also indicate rapid excretion of vinyl chloride in expired air. This, again, is consistent with the high volatility and low solubility of vinyl chloride gas. 20/ Watanabe, P.G., McGowan, G.R. and Gehring, P.G., Toxicol, and Appli. Pharmacol. 36:339--352 (1976). - 32 - ucc 010345 (8) For Operations Involving Polyvinyl Chloride/ the Types of Resin in Us , the Concentration of Vinyl Chloride Trapped in the Resinf and the Concentration of VC and PVC Oust in the Atmosphere Where Indi viduals Are Working. This Information Should Include Estimates of the Particles Sizes and Concentrations of Particles That Fall Within the Respirable Range and (9) In PVC Bagging and Milling Operations/ Atmospheric Levels of PVC and VC, Moni toring Devices Used to Detect VC, and the Type of Respirator Protection Program for Individuals Working in These Operations. This Should Include the Sensitivity and Validity of the Analytic Techniques in Use Information supplied to answer the inquiries cited above is likely to create confusion if used out of context. Past regulatory effort on the part of OSHA has resulted in the promulgation of regulations that covered resins contain ing any amount of contained vinyl chloride and materials that contained little or no vinyl chloride monomer; therefore it appears necessary to call OSHA's attention to all aspects of the industry. Operations involving polyvinyl chloride are broken down into the following sections: 1. Manufacture of PVC 2. Distribution 3. Compounding 4. Fabrication into semi-finished materials 5. Conversion of semi-finished materials to finished products - 33 - UCC 010346 The manufacture of synthetic resins (PVC) from vinyl chloride and other monomers involves reacting these monomers in agitated pressure vessels in the presence of catalysts in such a way that these liquids and/or gases are converted to solid resins. A considerable amount of heat is generated by the reaction. This is removed by cooling the vessel. As the monomer is converted to polymer during the reaction, the rate of reaction slows down. The unconverted monomers are removed from the reacting mass by heat and vacuum, and the resin (PVC) is recovered as a dried powder or as a latex or solution. The polymerization reaction may take place in pure monomer, in a solution, in a water-monomer emulsion or in a water-suspension of monomer. The nature of the poly merization process determines the nature of the subsequent recovery process and the nature of the resin particles pro duced. Currently there are four basic vinyl chloride poly merization techniques; 1. Suspension 2. Emulsion/Dispersioa3. Bmlk 4. Solution Suspension polymerization is the major process used for the manufacture of PVC resins and is used for about 8285% of C.S. production. (Figure 1). It involves the char ging of one or two parts water and one part vinyl chloride ** 34 a* ucc 010347 VC HO NOME It WATER SUSPENDING AID INITIATOR UHi WATER SUSPENSION POLYMERIZATION PROCESS IIGURE 1 ucc 010348 monomer or co-monomer mixture to an agitated reactor along with initiator and suspending agents. The mass is reacted at 50 to 65C until about 85-90% of the monomer is converted to resin. The resin-water mixture is then heated, sometimes under vacuum, until the unconverted monomer is substantially removed. The resin is then removed from the water and dried in rotary, flash or fluid bed dryers by exposure to heated air. The dried resin is transferred to storage silos prior to shipment in bulk containers or in paper bags. If only vinyl chloride monomer is reacted, the product is homopoly mer PVC. If a monomer such as vinyl acetate is mixed with the vinyl chloride, then a co-polymer PVC is produced. Resin products of the suspension resin process are many and varied in terms of molecular weight, composition, particle size, monomer retention, heat stability and ultimate use. A general description of the various grades of resins follows: (a) General purpose homopolymer for flexible mate rials such as shower curtains and wire insula tion are porous, large particle ("100 microns or more diameter) size, high molecular weight resins with good heat stability and low monomer retention characteristics. These resins contain essentially no particles less than 10 microns in diameter and the residual monomer content is in the range of non-detectable (N.D.) to 25 ppmw.21/ Particle porosity is a critical property. 21/ Particles 10 microns or larger in diameter are considered non-respirable. 36 - UCC 010349 (b) Homopolymer resins for pipe manufacture are dense, large particle size (~100 microns in diameter), high molecular weight resins with good heat stability. Monomer retention char acteristics are medium to low. These resins contain essentially no particles less than 10 microns in diameter and residual monomer content is in the range of N.D. to 30 ppmw. Generally the lower the molecular weight the higher the monomer retention. Particle density is a cri tical property. (c) Homopolyraer resins for rigid extruder shapes and calendered rigid sheeting are dense, medium particle size ("80 microns in diameter), medium molecular weight resins with reasonable heat stability and medium monomer retention charac teristics. These resins contain essentially no particles less than 10 microns in diameter and the residual monomer content ranges from N.D. to 50 ppmw. Particle density is desirable and porous particles are difficult to produce. (d) General purpose copolymer resins for rigid sheet ing, molding and flooring are medium particle size ("30 microns in diameter), glassy to low porosity, low to medium molecular weight, and high in monomer retention with poor heat sta bility. Comonomer content ranges up to 20%. The monomers most often used are vinyl acetate and vinylidene chloride. These resins contain essentially no particles less than 10 microns in diameter and residual monomer in the range of 100 to 300 ppmw. The poor heat stability coupled with the glassy particles make vinyl chloride monomer removal difficult. Copolymer resins offer ease of fabrication and have the ability to take up high loadings of fillers and pigments. (e) Copolymer resins for coating applications are low molecular weight, medium particle size ("75 microns in diameter), glassy non-porous par ticles, poor in heat stability and high in monomer retention. Co-monomer content ranges up to 40%. These resins contain few particles less than 10 microns and residual vinyl chloride monomer contents of 25 to 100 ppmw. - 37 - ucc 010350 (f) Plastisol additive resins for dispersion resin fabrication are medium molecular weight, small particle size ("25 microns in diameter), low in particle porosity, and medium in heat sta bility materials. The addition of these re sins to a dispersion resin plastisol reduces the plastisol viscosity and reduces the pro duct cost. The ability to perform uniformly in a plastisol is critical. These resins con tain appreciable quantities of particles smaller than 10 microns in diameter and contain N.D. to 25 ppmw of residual vinyl chloride monomer. Suspension process plants are generally meeting the permissible personal exposure limit of 1 pprav TWAg imposed by the OSHA Standard but are having difficulty meeting the 5 ppmv ceiling value without the use of respirators. Cer tain tasks, such as maintenance, cleaning and correcting process upsets, involve personnel exposure to brief periods of high vinyl chloride concentrations. These personnel are protected by continuus air-supplied respirators. Elimination of all use of respirators cannot be considered a realistic requirement. Suspension PVC, except for plastisol additive resins, presents no hazard from exposure to respirable dusts since these resins contain essentially no particles less than 10 microns in diameter. Indeed, except for the plastisol ad ditive resins, the use of cyclone collectors on resin dryers and resin transfer systems obviates the presence of such particles in suspension resins, i,.e., such particles are lost in the dryer exhaust. - 33 - ucc 010351 ucc 010352 ucc 010353 Emulsion/dispersion polymerization is the second most widely used process for the manufacture of PVC resins and amounts to 10-12% of total U.S. production. One of the important things to understand about emulsion polymerization is that it is not a single process but a family of processes, each producing specialized products that are defined or speci fied in terms of performance in a particular application. In the interest of brevity only the two major process families, the water soluble initiator system and the oil-soluble ini tiator system, will be discussed. (Figure 2). In the water soluble initiator system one to two parts water, one part monomer, 0.01 to 0.03 parts surfactant and water-soluble initiator (a redox system or a persulfate salt) are charged or fed to an agitated reactor and reacted at 30 to 60C to form a latex emulsion. The reactor agita tion must be sufficiently vigorous to emulsify the monomerwater mixture but not so vigorous that the latex is desta bilized. When 80 to 95% of the monomer is converted to poly mer the latex may be gently stripped of the unconverted mono mer with heat and vaccum or it may be subjected to a second initiator treatment and reacted to essentially 100% monomer conversion. The product of this polymerization may be simply filtered and shipped to consumers as a latex for use in the manufacture of coatings, mastics, laminations, and the like, or the polymer may be recovered as a dry resin. Recovery techniques vary. The most commonly used is to spray-dry 41 ucc 010354 EMULSION POLYMERIZATION PROCESS IIGURE ? ucc 010355 the latex, though some resins are recovered by coagulating the latex and dewatering with subsequent drying o the coagulura (resin). in the oil soluble initiator system one part monomer containing an organic peroxide is emulsified in one to two parts water containing 0.01 to 0.03 parts surfactant. The resulting emulsion is reacted at 30 to 60C to form a latex. From this point onward the oil soluble initiator system is similar to the water soluble initiator system. The choice of process depends to a great extent on the ultimate use of the resin. If resin particle size is critical the oil soluble initiator system is preferred. The resin particles formed during emulsion polymerization range in size from 0.05 to 2 microns. In the course of re covery and drying these may be agglomerated to particles as large as 30 microns. For some uses the agglomerates may be ground to a median particle size of about two microns. The small particle size results in rapid loss of residual vinyl chloride so that the resin contains only about 1 ppm free monomer. Because of handling problems nearly all the resin is bagged. In this process, the small amount of mono mer retained easily escapes before the resin arrives at a fabricating plant. Some proprietary dispersion resins, how ever, have material handling properties comparable to larger particle size suspension resins. These can be shipped, stored, conveyed and processed in bulk instead of in bags. - 43 - ucc 010356 Resin products of the emulsion process are more difficult to list because most products are sold on a performance ba sis as opposed to suspension products which are sold largely on specification and price. A rough classification is as follows: (a) Plastisol resins are the major emulsion pro cess products. These are very small particle size (2 to 3 micron diameter), non-porous, very high molecular weight, 100% vinyl chloride re sins with good heat stability and low monomer retention characteristics. These resins consist of particles less than 10 microns in diameter, contain significant amounts of surfactants and about 1 ppmw of residual vinyl chloride mono mer. When stirred into approximately 60 parts of plasticizer per hundred parts resin, these resins yield a viscous liquid plastisol which, when baked, fuses to a flexible vinyl plastic. (b) Foam resins are substantially the same as the plastisol resins except that they are medium molecular weight instead of high. The lower molecular weight yields a plastisol which fuses near the temperature at which a blowing agent yields up its gas. This is how a stable plastic foam is formed. (c) Organosol resins are a special variety of plasti sol resin primarily used for metal coating. If a high molecular weight PVC homopolymer dis persion resin is very finely ground and the remaining agglomerates are loosely bound together, it can be blended further with ketone, naphtha, pigments, stabilizers and adhesion promoters to yield a liquid coating material. This or ganosol is coated on metal and baked to provide a tough, abrasion resistant coating. (d) Specialty resins are an assortment of materials that make use of the flexibility of the emulsion process for their manufacture. These are made from vinyl chloride in combination with other monomers. The resins are recovered from the latex by coagulation and subsequent drying. Uses of these materials range from film for food packaging to modifiers for other resin fabrication. Further characterization of these 44 ucc 010351 materials is not possible, and they are men tioned here only to call attention to the fact that these important resins are impacted by vinyl chloride and polyvinyl chloride regula tions. (e) Latexes, too, are an assortment of materials generated by the flexibilty of the emulsion process. These are liquid materials containing 40 to 30% resin solids emulsified in water. Latexes containing resin solids high in vinyl chloride content are usually formulated with plasticizers and solvents and applied to a sub strate. The substrate is heated or baked to yield a resin film. Latexes containing resin solids low in vinyl chloride content will yield a resin film when the latex coating is simply air dried. These latexes find major use in latex paints, impregnants, mastics and adhe sives. Since both types of latexes are used as liquids, there is obviously no possibility of PVC dusts. Depending on the latex produced, most PVC latexes contain less than 10 ppmw of residual vinyl chloride monomer. This monomer is released slowly, and employee exposures in subsequent formulating and use is rarely over 0.5 ppmv. As is the case with suspension PVC process plants, emulsion process PVC plants are generally meeting the OSHA permissible exposure limit of 1 ppmv TWAg for employees. However, these plants, too, are experiencing difficulty meeting the ceiling limit without reasonable use of respira tors. The manufacture of dispersion PVC resins represents a source of respirable PVC dusts, and dust respirator use is usually required in dusty locations such as bagging. Certain proprietary dispersion resins do, however, have low dusting properties which greatly simplify control of the workplace dust normally associated with handling dispersion resins. 43 - ucc 010358 ucc 010359 ucc 010360 3ulk polymerization is the third major process in terms of volume for the manufacture of PVC resins but ac counts for only about 5% of U.S. production. (Figure 3). The process involves the charging of vinyl chloride mono mer and initiator to a first stage polymerizer where about 10% of the monomer is converted to polymer. This batch is then transferred to a second stage polymerizer where addi tional monomer and sometimes initiator are added. The poly merization is continued until about 80-85% of the monomer is converted to polymer. The unreacted vinyl chloride is removed by heat and vacuum and the finished resin product transferred to storage bins for later shipment to fabricating plants. The absence of water in the polymerization stage eliminates the need for the drying step. The advantages of the bulk process are its simpli city/ the uniformity of the resin particle size/ the high porosity of the resin particles/ the purity of the polymer (no soaps or suspending aids) and the granular/ low dustiness of the product. The disadvantages are less flexibility in product mix (homopolymers only) than the suspension process and poorer removal of residual monomer. These bulk process resins are competitive with suspension process PVC homopoly mers. Sulk process PVC resins are used in applications where clarity of the finished plastic, uniform resin particle size and high resin particle porosity are desired. A sim ple classification of their uses is as follows: - 48 - ucc 010361 010362 HULK POl YIIERIZATIOM PROCESS 8 riGIIIlE 3 (a) Rigid and flexible plastic materials produced by extrusion and calendering requires resins with large porous particles (100 microns in diameter), good heat stability and low monomer retention. These medium molecular weight homo polymer resins contain essentially no particles less than 10 microns and the residual VC mono mer content is less than 50 ppmw. (b) Rigid plastic moldings, plastisol additive re sins and powder coatings are made from low mole cular weight homopolymers with a particle size of 75 microns. Particle porosity is good and monomer retention is low. There are few par ticles less than 10 microns in diameter and residual vinyl chloride content is less than 50 ppmw. Bulk process plants have the same general types of personnel exposures to vinyl chloride noted for suspension process plants. Solution polymerization is a process unique to one company and accounts for about two percent of the total resin produced. (Figure 4). Vinyl chloride monomer, co-monomer, solvent and initiator are fed to a continuous reactor system. The polymer formed is soluble in the reacting mass so that the reactor product is a viscous resin solution. This solu tion is distilled to remove the unconverted monomers and the resin is recovered by treating the resin solution with water and drying the product. The resin particle is very porous, is always a copolymer, is free of soaps and suspend ing agents, has a median particle size of 75 microns and contains less than 0.2 ppm residual vinyl chloride. Solution process PVC resins are very often confused with suspension process resins for solution application. Molecular weight - 50 - UCC 010363 rit;ijh !: 4 SOI.VKM I VINYl. RESIN PROCESS WATER VENT 010364 WASTE WATER of these resins ranges from low to very low to achieve solu bility in solvents. Essentially all these materials are used for coatings in combination with other resinous mate rials. The solution PVC resin process, because of its na ture, exposes personnel to vinyl chloride concentrations below 0.5 ppm. The resin contains essentially no particles less than 10 microns in diameter. In addition to the resins produced by the four basic processes there are resins which are chemically modified in a second operation after the resin has been produced. The major product in this area is chlorinated PVC. In the coatings area copolymer resins are often modified through reactive sites in the co-monomer. These materials are men tioned only to note their existence and to point out that the very nature of chemical modification and subsequent pro cessing removes all possibility of their release of vinyl chloride in subsequent applications. Distribution of PVC resins poses some potential for personnel exposure to vinyl chloride monomer and to polyvinyl chloride. The structure and the economics of the distribu tion system have acted to cause such exposures to be minimal except for certain special situations. Suspension and bulk process PVC resins, except for plastisol addition powder coating, solution coating and ex- -52- UCC 010365 port sales move from the producing plant to the user via bulk carriers such as rail cars (containing approximately 150.000 pounds) or hopper trucks (containing approximately 35.000 pounds). These carriers are loaded via gravity from overhead bins or by pneumatic conveyor. The carrier is sealed during transit. On arrival at the delivery site, the carrier is unloaded by pneumatic conveyor to a storage silo. There is some vinyl chloride monomer emitted during the loading and unloading process, but personnel exposure is well below the OSHA Standard "action level". Monitoring of this operation when the resin contained 800 ppmw of resi dual vinyl chloride monomer showed personnel VCM exposures of approximately 1 ppmv TWAg. Although there is no recent data, with current residual VCM levels of approximately 50 ppm, one would expect personnel exposures to be down around 0.1 ppm TWAg. There is some resin dusting and spillage in the loading and unloading process, but the relatively large particle sizes and remote contact by personnel obviate any potential hazard. The bagging of the 5 to 10% of suspension and bulk process resins that are handled in this fashion is highly automated and messy, but personnel exposure to dusts or VCM are negligible. Resin is delivered to the packaging machine via gravity or pneumatic conveyor. The packaging machine operator inserts the filling tube into a filling valve-type kraft paper bag and actuates the machine to fill the bag. The filled bag drops off the filling tube to a conveyor and - 53 ucc 010366 the operator repeats the operation with another bag. Filled bags are automatically or manually stacked on pallets which may be stored in a warehouse awaiting shipment or may be loaded on a truck or railcar immediately. When the filled bag drops off the packing machine a small puff of resin and air is emitted from the bag valve as it closes. Subsequent handling of the bag causes some shifting of resin out of the valve. There are also faulty bags which may break on filling. Thus, the resin bagging area is usually messy. However, monitoring conducted in these areas indicates personnel vinyl chloride exposures are less than the OSHA Standard "action level." Dust measure- * ments for suspension and bulk resin bagging show less than 1 mg/m3 respirable dust. Bagging and storage of suspension and bulk process resins causes a significant reduction in the residual vinyl chloride content of the resin. Tests of moderately porous medium molecular weight resins show a reduction of over 50% in free monomer after one week. Handling and transport of suspension and bulk PVC resin in bags via truck or rail car appears to present no unusual hazards if normal work space ventilation standards are met in storage, loading and un loading resins. Except for some special situations where bulk trans port or fiber drums are used, essentially all emulsion pro cess PVC resins are packaged in kraft paper multi-wall bags. The bagging operation is essentially the same as that de- 34 - UCC 010367 scribed for suspension and bulk process resins. Vinyl chlor ide exposure is less than the OSHA Standard "action level." The NIOSH study by Mr. J.H. Jones in 1974 indicated that exposure is not likely unless it comes from emissions in adjacent operations.^/ Dust exposure is potentially a problem due to the resin's small particle size but local ventilation can control this readily. Current dust monitor ing shows respirable dust less than 5 mg/m3. The storage and truck shipment of emulsion PVC resins offer minimal vinyl chloride exposure opportunities for per sonnel. Warehouse and closed truck vinyl chloride monitoring show levels well below 0.5 ppmv vinyl chloride in the air. Solution process PVC resins are also packaged pri marily in kraft paper multi-wall bags. Bagging is essen tially the same as described for suspension resins. The NIOSH study in 1974 indicated vinyl chloride exposure to baggers of N.D. to 0.7 ppmv and total dust of less than 2 mg/m3. Vinyl chloride exposure currently is about 0.1 ppmv with no change in total dust exposure. Respirable dust is about 0.1 mg/m3. Monitoring of storage and truck shipment of solution process PVC resins usually shows undetectable amounts of 22/ Jones, J.H., Worker Exposure to Vinyl Chloride During Production and Fabrication of Vinyl Chloride and Poly vinyl Chloride. Study conducted with the Bendix Cor poration under NIOSH Contract CDC-99-74-50. Draft of this Report is at Appendix Q. See ?. 36. - 55 - ucc 010368 vinyl chloride monomer. Polyvinyl chloride latexes are most often handled and shipped in tank cars or trucks and in fifty-five gallon drums. There is some emission of vinyl chloride during loading and unloading operations but, if the latex contains 10 ppraw residual vinyl chloride or less, the personnel ex posures are less than 0.5 ppmv. Dust is not a problem with latex shipments. Compounding a PVC resin or latex means the mixing of that material with pigments, stabilizers, plasticizers, fillers and other additives to yield an intermediate material for subsequent conversion into finished or semi-finished products. In major plastics operations this is simply a single process step in a large integrated factory, but in the specialty resin area, as well as with small plant opera tions, a compound is produced by one plant and is subsequent ly shipped in a container to the user. Thus, in terms of regulation, these materials are classified as polyvinyl chlor ide. Often, however, the properties of the material are completely dissimilar to the PVC resin raw material, i.e., the vinyl chloride monomer content is diluted or reduced by heating and dustiness is reduced sharply or eliminated completely. Some examples are pelletized PVC compounds, powder blends, organosols, plastisols, lacquers, dry blends, and latex paints. The purpose of compounding is to combine the resin and additives into a homogeneous state suitable for further - 30 UCC 010369 processing. The level of compounding ingredients employed for PVC is substantially higher than for most plastics. Resin content of a compound may vary from 99% for rigid sheet ing to 15% for floor tile. Some compounding ingredients introduced in PVC fabrication are as follows: (a) Plasticizers are high boiling temperature esters of phthalic acid, adipic acid, azelaic acid, phosphoric acid and so on. Epoxidized oils, epoxy resins, and polyester resins are also used. (b) Heat stabilizers are compounds of lead, barium, cadmium, tin and zinc. Epoxies and phosphites are also used. (c) Fillers consist of clay, talc, mica, asbestos, calcium carbonate, titanium dioxide, diatomaeeous earth and barytes. (d) Pigments may be inorganic compounds, such as titanium dioxide, chromium oxide, ultramarine blue or molybdate orange, or they may be organic compounds, such as phthalocyanine, quinacridone and benzidine salts. (e) Modifying resins improve processing character istics and impact resistance. These are acry late, ABS, and chlorinated polyethylene resins. (f) Lubricants make subsequent processing easier. Some of these are waxes, stearic acid and metal stearates. (g) Light stabilizers provide ultra-violet light resistance. Examples are benzotriazoles or benzophenones. (h) Fungicides give resistance to fungal attack. Materials commonly used are amines, arsenates and organotins. (i) Flame retardants, such as antimony oxide and the boranes, are used where plasticizer con tent is high. - 57 - UCC 010370 (j) Anti-static agents reduce dust and dust pickup. These are often amine compounds. (k) 3righteners yield a whiter, clearer film. (l) Anti-oxidants, such as bisphenol A, are some times used. Additionally, particularly in the coatings area, there are specialized additives such as surfactants, pig ment wetting aids, solvents, and diluents. These compounding ingredients and additives are men tioned in some detail to show the difficulty of isolating causative agents if an employee health problem is believed to exist in the PVC fabricating area. It is certainly a mistake to attribute dust problems solely to PVC dust and toxic vapor problems solely to vinyl chloride monomer. Compounding PVC resins for subsequent fabricating via calendering, extrusion or molding involves two basic steps; dry or powder blending followed by melt compounding. The choice of equipment is important because variations in the homogeneity of the resin compound may cause serious de ficiencies in processing and in the finished product. The calendering, extrusion and molding operations involve large scale operations with suspension and bulk process PVC resins which are almost always handled in bulk. Resin is charged from a bulk silo to a weigh hopper and dumped into the mixer. Plasticizers are metered into the charge. Other additives are charged by similar techniques though small volume addi tives may be first mixed into a portion of the plasticizer. - 53 - UCC 010371 The mixer is closed and heat is applied externally or gener ated by the shear action of the mixer itself. The charge is subjected to mixing and heat (approximately 200-250F) for some predetermined time or until the mass is a dry pow der. Gases from the charge are vented outside the work area. On completion of the dry or powder blending, the mix may be cooled and stored for subsequent use or charged directly to a high intensity mixer or to an extruder. The mixers and/or the extruder melt the dry or powder compound blend to secure a hot plastic mass. For calendering, the mixer or extruder charge is transferred to the calender where it is formed into flexible film or into rigid sheets as semi-finished products. For extruded products, the ex truder may simply be fitted with a die, as in the manufacture of pipe, to form the finished product. The industrial hygiene survey carried out by NXOSH in 1974 and 1975 indicated that vinyl chloride monomer exposures for this type of operation in the range of N.D. to 0.6 ppm. (See attached Table 33 from the NIOSH report). With the current low levels of re sidual vinyl chloride monomer in suspension and bulk process PVC resins, vinyl chloride monomer exposure is negligible. Dust is a problem in calendering, molding and extru sion processing but as Mr. Jones points out in his NXOSH report the dust is probably not all PVC since fillers and other additives are used. Mr. Jones does not mention, how ever, that plasticizer aerosols formed during processing - 59 - UCC 010372 Tabit 33 Sunsarr of ?tsy 1 Chlori,dt Sis liag --All :ibri.cation ? ;is:f s b* Job n Calender Personnel IS Cospoundlag Personnel 78 Intrusion Personnel 58 Lab Personnel 18 Maintenance Personnel 10 Holding Personnel 16 Plastisol Sipping Personnel 40 Miscellaneous Personnel 20 Total of Personal Staples 268 Cosposice of All Ares Seales 32 _* X (ppm) 0.57 O.U 0.09 0.08 0.01 , <0.01 0.01 <0.01 0.14 0.04 X (pptt.) 0.24 0.05 0.04 0.05 <0.01 <0.01 <0.01 <0.01 0.03 0.05 Lange (pptt) KD-2.4A ND-0.69 NO-0.76 HD-0.68 ' HD-0.02 KD-0.03 HD-0.06 HD--0.01 HD-2.44 K2-0.68 * x TWA ucc 010373 also appear as part of the total dust measurement. (See attached Tables 30 and 32 from the NIQSH report along with flow sheets for calendering, pipe extrusion and flexible film extrusion). Plastisol techniques for compounding and fabricating PVC involve the use of dispersion process PVC resins along with plastisol additive resins from the suspension and bulk PVC processes. The principal advantages to this fabrication technique are low investment in fabricating equipment and flexibility in changing from one product to another, A basic plastisol might consist of 100 parts dispersion process PVC resin, 55 parts dioctyl phthalate plasticizer, 5 parts epoxy plasticizer and 3 parts barium, cadium, or zinc liquid sta bilizer. Heating the plastisol to 350-375F fuses it into a flexible homogeneous plastic. In practice, however, the only time this simple formulation is used is to test resins. Additive resins are used to reduce cost, to alter the plasti sol viscosity and to increase the hardness. Reactive resins, such as epoxies and acrylates, are added for hardness. Pig ments are added for color and opacity. Anti-foamers reduce foaming during deaeration and fusion. Plastisol preparation is carried out in a slow speed, unheated mixing vessel. Plasticizer is weighed or metered into the vat and followed by the requisite number of bags of various resins, fillers and so forth. When the mixture is homogeneous, it is either transferred to a deaerator or - 61 - ucc 010374 :: 30 rclr^^T'- Cil=r^d Ou*r Sensing U:i S' *- - * lacnrlas Ku; Slender " " " Near Mixer B lien; Calendar " Dttsz Caasesgr*: :lsr ac>sJ 11.3 1.21 6.6: 8.75 11.67 10.0 6.06 11.67 8.33 62 - ucc 010375 i: Jsir^T- -iicTid* >ut c?liag Caia y^j-* v laeatiss cu Slaa*7 Ar** y'-' Lni laabury vix>; iru C^liadcr iru ?l*StlSoi IJiSiag Rdos Cut ?tla lias rxisi Caase.;r*si3=. /Z' 6.67 1.67 6.67 . 13.33 6.67 7.9 7.27 - 63 - ucc 010376 PiMtuclion FIGURE IV--11 TYPICAL CALENDERING OPERATION ucc 010377 FIGURE IV-B FLEXIBLE FVC FILM EXTRUSION UITII IN-PLANT COMPOUNDING ucc 010378 I Oo\k I ucc 010379 V.nl i at -i l FIGURE IV-12 SOLVENT CAST rvc FILM PRODUCTION ucc 010380 the mixing vessel may be closed and a vacuum applied to remove entrained air carried in by the solid components. After deaeration the plastisol is ready for fabrication. It may be coated on a release paper, on a metal substrate or on a fabric. These items pass into an oven where the plastisol is fused to yield a plastic film which may be stripped from the release paper or a coated metal sheet or fabric. The plastisol may be poured into metal molds which are subsequently heated. This fuses the plastic for later removal from the mold. To produce foamed plastic, the plas tisol may be mechanically frothed or a blowing agent such as an azide can be added. The blowing agent releases gas during the fusion step and the result is a sponge-like plas tic. Plastisol fabrication is likely to be less sophis ticated, involve smaller plants and be more labor intensive than conventional PVC fabrication. In such operations, the potential for exposure to PVC dust and vinyl chloride monomer is usually greater. Dispersion PVC and PVC plastisol addi tive resins are low in residual monomer content when manufac tured and are usually shipped and used in paper bags after a considerable time lag for analysis and warehousing. Ac cordingly, vinyl chloride monomer exposure in this type of operation is minimal. The attached table from the NIOSH survey in 1974-1975 could be said to be representative of the VCM exposures in plastisol operations. -sa uce 010381 Exposure to dust may be considerable in these opera tions due to the small particle size of dispersion and ad ditive PVC resins as well as the small particle size of the fillers and pigments. During the fusion step plastisols also give off plasticizer aerosols which appear as a part of total dust. Because dust control is largely an individual matter for each installation to resolve based on plant con figuration and the like, no generalized statement can be made for the industry except to point out that the dust is not wholly PVC. Organosols are a specialized version of a plastisol. Ketones, esters and hydrocarbons are added to the plastisol to yield a low viscosity liquid composition which is sprayed, roller-coated or brushed onto a substrate. The resulting coated substrate is baked to drive off the diluents and fuse the coating. Solution coating is a small, specialized area of PVC resin fabrication. PVC resins dissolved in organic sol vents and applied to a suitably prepared substrate yield coatings with excellent resistance to water, alkalis, acids and weather. The resins used are copolymers produced by solution polymerization or by special suspension resin pro cesses. These resins must be exceptionally free of electro lytes and insoluble materials. The resin typically is dis solved in a mixture of toluene, methyl ethyl ketone and methyl isobutyl ketone. Pigments and stabilizer are added - 59 - UCC 010382 :u.i Sussary Cf tiSTl Oiloridt Sa=slx=s 5axi by Jo'; il :a.irioario:. "lax: I Job lAb Ptrsoeatl ?L*s:iaol Ptrsoaatl Toral of ?*1*06*1 Saaplss Cocsexlt* of AH Atm Sxap Its .* X e Cp?s) 4 SB 40 0.01 44 <0.01 4 SB X C??a) SB o.o: <0.01 KB SUxgt (.77*' KB KB-0.06 ro-o.06 3D * X - TWA - 70 - ucc 010383 and the mixture "ground" in a colloid mill or similar device. The resulting coating is sprayed on the substrate and either oven or air-dried. Each coating is formulated for perfor mance in certain areas and coating formulations are closely guarded by individual formulators. Formulation of coatings is a small scale operation generally dealing with resins in paper bags and solvents in built. There is little or no exposure to residual vinyl chloride monomer from most solution resins since VCM is vir tually non-detectable in the resin. Dust exposure from re sin and pigments is low because only small volumes are handled. Most formulators have fume control systems for control of solvent vapors and these also remove dusts from the work area. Monitoring for vinyl chloride monomer at coating for mulators generally shows non-detectable to 0.05 ppmv. Solvent cast PVC film is a small fabrication opera tion which is based on solution coating with solvent recovery. Higher molecular weight resins are often used to achieve higher film strength. A high solids vinyl resin solution is cast on a stainless steel belt. Heat drives off the solvent until a very thin transparent film can be stripped off and dried further on heated rolls. The solvent is col lected and reused. More expensive solvents, such as tetrahvdrofuran, are often used to reduce solution viscosity. Exposures to dust and vinyl chloride monomer are similar to that of a coating formulator. PVC and PVC copolymer dispersions are produced for - 71 - ucc 010384 use in latex form for coating, binder and saturant appli cations. These latexes fall into two categories. One is a PVC homopolymer or copolymer, high in vinyl chloride con tent, for industrial use. The second is a copolymer latex containing less than 50% vinyl chloride in the polymer. This type of process forms films drying the latex at ambient temperature. Latexes are formulated with the additives listed earlier for vinyl resins plus thickeners, surface active agents, colloids, solvents and anti-foamers. Open or semi open vessels equipped with low speed, low shear agitators are used for formulation. Oils such as plasticizers are often emulsified with water prior to addition to the mix. Depending on the latex the finished compound may be applied to a substrate by dipping, roller coating or spraying and the coated substrate baked to fuse the resin and drive off the water or it may simply be applied and air dried as a latex paint. When pigments and fillers are used, dust is a poten tial problem during the charging of the formula mix. There is, of course, no PVC dust. Residual vinyl chloride monomer in the latex is controlled by the latex producer. Latexes containing 10 ppmw or less RVCM do not emit enough vinyl chloride monomer during formulation or application to cause employee exposures in excess of the OSHA standard "action level". Latexes containing more than 10 ppmw RVCM are usually processed under controlled conditions where employee exposure - 72 - ucc 010385 is within the prescribed limits. The PVC resin industry is very large, and the ver satility of the products is such that all uses and modes of application cannot be covered in this brief overview. Others include powder coating, blending resin for polyethyl ene wire compounds, and rug fiber flame proofing. Health hazards in these applications are negligible. Conversion of semi-finished PVC plastics to finished products involves drilling, cutting, welding, and heating of the material. Considerable concern has been expressed by many persons that heated PVC will breakdown to its monomer or that enough residual VCM is contained in the product to be emitted during heating or welding. There are a number of studies by NIOSH, EPA and others that conclusively show that this is not the case although there can be evolution of plasticizer fumes, acetic acid, hydrogen chloride and, ultimately, oxides of carbon when PVC is heated. Trace amounts of vinyl chloride have been detected in some cases but only after considerable production of irritating gases which would preclude employee inhalation. As regards vinyl chloride monitoring devices where there is potential massive exposure to vinyl chloride via leaks, vessel rupture or emergency discharge, the most ef fective monitors are those automatic systems based on organic vapor detection, chromatographic analysis, and infrared ab sorption spectroscopy. These give prompt warning of such VCM emissions and permit prompt protective action by the - 73 - UCC 010386 employee. Portable units such as the HNu unit or the Century Systems Corp. OVA-98 are extremely useful for leak control and on the spot monitoring. Respirators in use for vinyl chloride protection are those prescribed by NIOSH. Most vinyl chloride and poly vinyl chloride producers rely heavily on self-contained breathing air units or hose-fed breathing air masks. - 74 - ucc 010387 (10) Types of Occupations, Job Classi fications, and Industries Where Where Exposure to Either VC or PVC At Any Level May Occur, and The Num bers of Employees Involved in Each Vinyl Chloride and Polyvinyl Chloride Exposure Situation, Separated By Sex and Race As to the types of occupations, jobs and industries presenting a potential for exposure to either vinyl chloride or polyvinyl chloride, SPI is unaware of any change in these areas whatsoever since the time of the initial OSHA rule making on vinyl chloride. As the industry trade association, SPI neither has nor collects data on the numbers of employees involved in each exposure situation, separated by sex and race. - 75 - ucc 010388 (11) Appropriate Engineering Controls, Work Practices, and Personal Pro tective Equipment Available to Re duce Levels of Exposure to VC or PVC Below the Current Standards Or To the Lowest Levels Feasible The Society is informed that the individual company members of the PVC Safety Group are presently engaging in the use of appropriate engineering controls, work practices and personal protective equipment to reduce levels of expo sure to vinyl chloride and polyvinyl chloride to the current ly permitted levels. As to vinyl chloride, the current standard for con trolling occupational exposure to VCM is sufficiently strin gent that great difficulty has been encountered by industry in coming into compliance with the standard that is currently in effect. Because of its stringency, not all work places are at all times in compliance with the current standard. In short, there are no feasible, additional engineering con trols, work practices and/or personal protective equipment available to reduce levels of vinyl chloride scientifically below the present exposure level. Therefore, it would seem that the current standard is the lowest level attainable * and that techniques to reduce the current exposure levels are not known. Furthermore, SPI submits that the present permitted exposure level is adequate to safeguard employee health. No new evidence has been presented to refute this conclusion. - 76 - ucc 010389 As to PVC generally, we know of no reason to control exposure to the polymer because polyvinyl chloride in any form is not a health hazard. In fact, PVC is so stable and inert that it finds use in such demanding applications as surgical implants, medical tubing and high voltage electrical wire. As to respirable dust which may be associated with certain operations involving PVC production, these dusts are currently governed by OSHA's nuisance dust regulations. 29 C.F.R. S1910.1000. Controls are utilized to comply with these regulations and to protect workers from any hazard which would be associated with exposure to the dust. Con sequently, extensive investigation into appropriate engi neering controls, work practices and personal protective equipment available to reduce the levels of exposure to PVC dust further are not areas known to us to have been investi gated in any great detail. As a final comment it should be noted that inasmuch as PVC dust has not been shown to be a health hazard at levels below those to which it is currently controlled (or at any other level, for that matter), we know of no purpose which would be served by speculating on methods to reduce levels of exposure. - 77 - IJCC 010390 III. CONCLUSION As to VCM. OSHA is aware of Maltoni's experiments which indicate possible effects in animals exposed to 10 ppm VCM. The Agency must also be aware that no increase of neoplasms was found in animals exposed to less than 10 ppm. Based on these and previous experiments, it is clearly evident that rodents are more susceptible to VCM than are humans. Accordingly, that cancer can be induced in animals at levels lower than previously reported seems to be of scientific interest only. The fact is that human experience should be given higher importance than animal studies, the animal data having predicted a cancer incidence rate over 500 times greater than that observed in man. The Agency also appears to be interested in another report from Maltoni to the effect that VCM can exert a car cinogenic effect transplacentally. This phenomenon, however, has only been demonstrated in pregnant rats exposed to very high concentrations of vinyl chloride. Additional work in this area needs to be conducted using lower, more realistic doses since available data indicate that the rates of meta bolism in the rat shift as exposure concentrations of vinyl chloride change* Of further interest to OSHA should be the fact that vinyl chloride did not cause significant embryonal or fetal - 73 - ucc 010391 toxicity and was not teratogenic in studies in rats, mice or rabbits. In fact, 3PI knows of no valid scientific paper associating vinyl chloride with human birth defects at any level of exposure. Regarding effects in humans caused by exposure to vinyl chloride, there is no new epidemiologic data on vinyl chloride exposed populations. The Society has, however, contracted for a complete, independent analysis of all avail able, relevant epidemiologic data. This is particularly important since it is not always made clear in subsequent papers reviewing them that many of the studies which have been reported represent investigations of the same population or subsets thereof. The next epidemiologic data on VCM ex posure is expected to be the five year update on the original Tabershaw and Gaffey study. The Society is informed that this study will soon begin under the direction of the Chemical Manufacturers Association and will be a straight forward epidemiology update with special emphasis on neoplasms of the brain. In the meantime, SPI is submitting to the Agency with these Comments the most recent compilation of all liver angiosarcoma cases associated with VCM. If mutagenic effects occur as monitored by chromo somal analysis of circulating lympocytes, it has been demon strated that they were the results of high exposures; the changes have not been permanent since they have been rever sible. The changes did not occur at lower levels of exposure. - 79 - uoc 010392 The clinical significance of the reversible changes observed is not known. Being a poorly soluble gas, vinyl chloride does not accumulate from chronic exposure but, rather, is rapidly exhaled after exposure ceases. Hence, there can be no body burden in the usual meaning of the term. Responsive to the Agency's questions about personnel exposure to VCM and appropriate engineering controls, work practices and personal protective equipment available to reduce levels of exposure to VCM below the current stan dards or to the lowest levels feasible, the VCM/PVC industry is presently using appropriate engineering controls, work practices and personal protective equipment aimed at achieving compliance with the existing standard. It must be recog nized by OSHA, however, that the Vinyl Chloride Standard is very stringent and industry is still encountering signi ficant difficulties relative to achieving full time compli ance with it. Although the industry has made tremendous strides in controlling VCM exposure, the variability in resin type and the resin type relationship to differing VCM expo sure potential has the industry in a position where the use of work practices and respiratory protective equipment to achieve day-to-day compliance with the standard is still wide-spread. Because of process variability no additional, feasible measures to reduce exposure levels significantly oelow the present level are known by the industry to exist. It would appear that they are all in use and that the present - 30 - ucc 010393 * s permitted exposure level is adequate to safeguard employee health. As to PVC. experimental studies show no carcinogenic or other toxic manifestations related to polyvinyl chloride exposure. Solid PVC has long been known to be inert and the effects resulting from experimental exposure to pvc dust appear to be characteristic of nuisance dusts in general. The effects appear to be similar in man, that is, they are limited to deposition of dust in the lungs in a manner which can cause slight effects to occur but no carcinogenic or other toxic effects have been observed. Regarding epidemiology or case reports of cancer associated with exposure to PVC, the only new information that SPI knows to be available is that presented by Dr. t Seaton at the Bethesda Symposium. As to that study and the others referenced in the Request for Information, it is The Society's position that PVC dust is adequately regulated by OSHA's general dust control standards and has not been shown to present any hazard at these low levels. As to the hypothesis that PVC dust carried into the lung can result in its being distributed throughout the body, SPI believes that, even were this hypothesis correct -- and it is not thought to be correct, the minute quantity of mono mer in PVC dust particles is so small that it would make this speculative exposure of no practical significance. In PVC manufacturing operations, both the quantity and size of dust particles vary depending on the resin - SI - ucc 010394 being handled. The same variability is inherent in the resi dual vinyl chloride in dust particles and other conditions which might be expected in manufacturing and fabricating different resins. In light of these conditions, appropriate control technology, work practices and personal protective equipment are employed as required. In addition to the information and views presented above, the Agency should be advised as noted in the body of this document that SPI has additional comments and infor mation to submit for the Record. These materials will be assembled and supplied to the Docket Officer when they are available. The foregoing considered, SPI's PVC Safety Group most strongly asserts that, based on the information being considered by the Agency in its reassessment of VCM, no data are available to suggest any new or greater hazard associated with occupational exposure to vinyl chloride. The Society is also steadfastly of the opinion that PVC dust is merely a nuisance dust and that no adverse health hazard information has been presented to change this position. Accordingly, SPI suggests that the available data indicate that both vinyl chloride and polyvinyl chloride are adequately regulated to protect worker health. Respectfully submitted. INDUSTRY, INC. 32 - UCC 010395