Document xzgQNN13gZYX9yRKm2qd4K7KE

Vista Chemical Company 15990 North Barker's Landing Road Post Office Box 19029 / r. -ion, Texas 77224 Phone (713) 531-3200 December 8, 1987 Roy T. Gottesman The Vinyl Institute 355 Lexington Avenue New York, NY 10017 SUBJECT: PAPER ON VCM CON1 AMINATION Dear Mr. Gottesman I met Dr. Kathleen Wolf at a recent conference on waste minimization, Subsequently, she sent me the attached reprint of her paper on VCM contamination. I thought you may be interested. Sincerely, jsetph C. Ledvina 'Director, Environmental Activities aj o Attachment SPI-00001 Journal of Hazardous Mali.rials, 15 (1987) 163-184 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands 163 VINYL CHLORIDE CONTAMINATION: THE HIDDEN THREAT* KATY WOLF, RICHARD HOLLAND and ARJUN RAJARATNAM The Rand Corporation, 170^ Main Street, Santa Monica, CA 90406 (U.S.A.) (Received August 1986; aocipted September 1986) Summary Vinyl chloride - an establi; ihed human carcinogen - has been found in groundwater and in gases emitted from sanitary landfil s. In many cases, the chemical itselfwas not placed in those locations and its origin is unknown. T1 is paper presents and analyses a number of possible origins. The two most likely include biotransfc imatron and chemical reaction. Biotransformation leading to a vinyl chloride end product has bee a observed in the laboratory. The analysis shows chemical reaction resulting in the formation oi' vinyl chloride might be favored in certain instances. The results suggest that further research, particularly focusing on these two routes, could shed light on the processes of vinyl chloride formation in the environment. 1. Introduction In the last several years, vinyl chloride (VC) has been detected in the air, water, and soil in locations where the substance was not disposed of or stored. This raises questions ab Dut the origin of the VC, an established human carcin ogen, about how widespread it is in the environment, and about its ultimate fate. Indeed, ifthe VC is being created through an environmental process, then concentrations may increase over time and human health may eventually be adversely affected. In this paper, we explc re the possible origin of the vinyl chloride. Our results suggest that there may be more than one source or mechanism of formation in land disposal sites and groundwater aquifers. The existing data are insufficient for a more rigorous analysis at the present time, and our conclusions are spec ulative and designed primarily to focus more attention on the question. In what follows in Section II, we describe several locations where vinyl chlo ride has been found. In section III, we present production and use data that suggest the chemical was probably not used or disposed of near these sites. Its presence, however, is of concern because of potential human health effects 'Views expressed in this paper are the authors' own and are not necessarily shared by the Rand Corporation or its research sponsors. 0.104-3894/87/$03.50 1987 Elsevier Science Publishers B.V. SPI-00002 -r I 164 which we alsc describe. In Section IV, we analyze six possible explanations of vinyl chloride's presence. These include formation through reduction by microorganisms, formation through chemical reaction, and migration of VC from various sources. In Section V, we summarize our results and make some concluding remarks. II. Sources of vinyl chloride VC has been found in trace amounts in the Santa Clara Valley. It was detected in the range of 50 to 500 parts per billion in the groundwater in the vicinity of three separate plants manufacturing electronics equipment [ 1 ]. Such plants use significant amounts of chlorinated solvents each year, most of which is stored in underground tanks. This so-called clean industry received a great deal of publicity in recent years when it was found that a number of the storage tanks were leaking. Because it is unlikely that these plants ever purchased VC for any purpose, its detection in the soil and groundwater in the area is curious. Another source also reports the presence of VC and groundwater in the same general area [2,3]. VC has, in fact, been found in groundwater in trace con centrations throughout the U.S. [4,5]. The chemical has also been detected in the gas collection systems and the ambient air surrounding hazardous waste disposal sites. At one such site BKK landfill in West Covina, California - VC was detected in spite of the fact that the firm had not accepted the chemical for disposal for some time [6]. Two separate industry sources indicate that VC has also been detected at the perimeter of sar itary landfills where only municipal trash was buried and where disposal of VC was never permitted. III. Background data on vinyl chloride Production and use In 1984, production of VC - called VC monomer - amounted to somewhat more than 6 bill ion pounds or about 2.7 million metric tons. VC is produced by eight manufacturers in eleven domestic plants. Virtually all of the VC pro duced today is used as an intermediate in the manufacture of polyvinyl chloride ( PVC) or other copolymers [7]. PVC is today used in a variety of products throughout the ;conomy including piping, tubing, flooring, textiles, coating, wire, cable, film photograph records, and bottles [8]. Prior to 1974, VC was used as an aerosol propellant in a variety of products such as pesticides, drugs, and cosmetics. Although manufacturers may have actually stopped using VC for this purpose for financial reasons, in 1974 three government agencies - the Food and Drug Administration (FDA), the Environmental Prote :tion Agency (EPA), and the Consumer Product Safety Com- SPI-00003 T 165 mission (CPSC) - banned VC's use in self-pressurized aerosols for household use [9,10]. Health effects The ban on use of VC in aerosol applicalions in 1974 was prompted by indis putable evidence that VC was a human ctrcinogen. At that time, Goodrich, a VC and PVC producer, announced that four of its workers had died of angios arcoma, a rare liver cancer. By the spring of 1968, 68 cases of the disease had been reported [10]. The highest incidence appeared in workers who cleaned the polymerization reactor where concent: -ations of VC averaged between 250 and 300 parts per million (ppm) and peak concentrations were as high as several parts per thousands. The results of animal studies confirm the unequivocal carcinogenicity of VC. In 1974, an Italian group reported that rats had developed angiosarcoma in inhalation studies with VC concentrations at 250 ppm [ 11 ]. Another experi ment conducted in 1975 reported angiosarcoma at 50 ppm [12]. Since then, other studies have verified that VC is a carcinogen through inhalation and ingestion [13]. There is today a consensus that VC is carcinogenic. The National Toxicol ogy Program lists it as one of the few do ten chemicals that are established human carcinogens [14]. Its identification in groundwater and at the perim eters land disposal sites therefore is cause for concern. IV. Vinyl chloride origins In what follows, we discuss several poss ible processes that could result in VC's presence in inexplicable locations, hese include anaerobic microbial transformation, chemical transformation, PVC outgassing, PVC depolymerization, emission from aerosol cans, and solvent contamination. We examine the first two - biotransformation and chemical transformation - in some detail and only briefly discuss the other processes By way of introduction, we first describe several chemicals that are widely used, disposed of in hazardous waste landfills, and stored in underground stor age tanks. Such chemicals include the industrial solvents 1,1,1-trichloroethane (TCA), trichloroethylene (TCE), and pe chloroethylene (PERC). Annual historical production of these chemicals is presented by Wolf and Chesnutt [ 15] and reproduced here in Table 1 for 1934. The values of Table 1 show that the comb ned annual production of the three industrial solvents is huge - 760 thousand metric tons. They are used in a variety of applications including the dry cleaning and metal cleaning indus tries. They are stored in underground tanks near businesses across the U.S. and are present in hazardous waste land disposal sites all over the nation. In SPI-00004 T 166 TABLE 1 Production of Chlorinated solvents - 1984 Solvent Production (thousand metric tons) TCA TCE PERC 306 200 260 Source: U.S.ITC [16];CMR [17], the discussion of VC origins that follows, we will refer to these chemicals frequently. Biotransforn mtion Three investigators have presented evidence that under the anaerobic con dition that exists in groundwater, certain chlorinated hydrocarbons are biod egraded. For reference, we show the degradation sequence in Fig. 1. tram-1* 2-4ich lororthy lent trns-l,2-0CE -------- i H Cl >C*<( Cl H perch! worthy!i PEC Cl Cl >CC( Cl Cl triehlororthylr Cl H >C=<1 Cl Cl cis-1,2-dich lorcrthy1m ci-l,2-8CE HH )OC( Cl Cl vinyl chloride VC HH -) IC-Cl Cl H l, l, l-tnctUororth*r|a 1,1, l-TCA l, l-dicMororther* 1,l-OCP Cl H cJ~ tl--H ii i Cl--ll 1-- .1H HI Fig. 1. Possible biodegradation sequence. cis*t,2-didilororthylem 1,1-XE Cl H -4 )CC< Cl H Cl H J-i- SPI-00005 T\BLE 2 B Kjdefradation half-lives Chemical PERC TCE 1.1-DCE cu-1.2-DCE trans-1.1DCE VC Half-life (days) 34 43 53 long* long* long* 1.1.1-TCA 1.1- DCA Chloroethane 16 long* 10 Source: Wood et al. [ 5 ]. Long means no detectable reduction of the chenfical over 30 to 60 days. l 167 1 1> The biotransformation steps each r(suit in the replacement of a chlorine atom in the molecule by a hydrogen ato . In the top sequence, a chloride atom in PERC is replaced with a hydrogen atom, transforming it to TCE. In the next step, substitution of one chlorine atom by a hydrogen atom in TCE can, in principle, lead to the three products, c,,'s- and tr<ms-l,2-dichloroethylene (cis1,2-DCE and trans-l,2-DCE) and 1,1- hloroethylene (1,1-DCE). In the third dt step, replacement of the third chlorine atom with a hydrogen atom produces the compound of interest - VC. In the> bo ttom sequence, TCA is first converted to 1,1-dichloroethane (DCA) which is Converted, in turn, to chloroethane. In one study, Wood et al. [5] identified VC, the three DCEs, 1,1-DCA, and chloroethane in an aquifer that supplips drinking water. The authors stress that these chemicals have no logical so'jirce since they are not produced or in wide use today.* The investigators iso ated and cultured anaerobic bacteria from groundwater and muck-water in tPe laboratory in the presence of PERC. From these experiments, the authors de ;ermined the biodegradation half-lives of the chemicals shown in Table 2. In both the current work and the earlier work, Wood et al. [5] found that the ratio of production of cis- 1,2-DCE to frams-l.l-DCE was at least 25 to one. Woodetal. [5] also examined a series of actual spills. In one such spill which occurred 15 years ago, concentrations of TCE, TCA, and PERC - the com monly used solvents - were still extremely high. In samples of water deeper in the aquifer or farther downstream from the spill site, concentrations of these "As discussed earlier in Section II, VC monomer , in fact, produced in huge quantities. It is true, however, that virtually all of it is converted into RVC. SPI-00006 168 TABLE3 Chemical concentr itions Sample Chemical (g/1) PERC Muck before incuba lion Muck after 21-day i icubation Groundwater-treatc lent plant Groundweter-spiU s te PERC 1,630 1.430 466 0.02 0.03 b TCE 30 18 78 0.29 + 0.14 426 45.7 1,1-DCE' 2 2.5 0.21 0.21 0.68+0.16 C14' 1.2-DCE b 63.3 25.6 3.4 1145 + 302 trans* 1,2-DCE b 1.8 1.6 0.4 4.9 2.4 Source: Parsons et al. (181. "The authors call this dichloromethane. See footnote in text for explanation. bLesa than detection limit of 0.5 g/1. 'Not measurable. I VC I 28.3 6.8 6.0 82.1 21.5 chemicals were lower and concentrations of their transformation products were higher. A second group - Parsons et al. [18] - found VC and cis- and trans-1,2-DCE in the groundwater in Southern Florida where local industries do not use the chemicals. Using water with indigenous microorganisms injected with PERC in the laboratory, the group demonstrated the formation of TCE and the other chemicals meas ired using gas chomatography* (GC) in muck but not in auto claved muck - the control. The results are summarized in Table 3. In the third sample - the muck after the 21 day incubation - Parsons et al. [ 18] found a P!RC concentration of 466 pig/\, a fairly high concentration of TCE (78 fi g/1, reasonable concentrations of the next sequence of compounds, 1,1-DCE and cii- and trans-l,2-DCE (67.6 /r g/1 combined), and a smaller concentration o: VC (28.3 fig/l). These data are certainly suggestive of the chain of successive reduction in Fig. 1. Note also that the Parson et al. [ 18] data agree with Wood et al. [5] in that cis-1,2-DCE formation is much favored over frans-1,2-DCE formation. Furthermore, the data of Table 3 also suggest even less of a tendency to form 1,1-DCE. The information in Table 3 on the actual groundwater measurements are also persuasive. At this site in question, TCE and not PERC was spilled and detected. Although the authors do not refer to the length of time since the spill, the high indicated conversions - especially to cis-1,2-DCE suggest it probably occurred years ago. McCarty [ 19] reports the formation of DCE and VC from PERC and TCE 'The authors also m<l< ntion that they found either dichloromethane (CH.CU) or l.l-dichloroethylene (1,1-DCE) it that the GC could not distinguish between them. With reference to Fig. 1, it is not likely that one-carbon chemical like methylene chloride (dichloromethane) would be present. The presenci of 1,1-DCE. on the other hand, would be expected - and it is clear this chemical was found. SPI-00007 169 in unpublished experiments conducted Ill his laboratory. Under anaerobic conditions, TCA and PERC were almost com]pletely transformed. In contrast under aerobic conditions, no biotransformatic n was detected. McCarty also states that the evidence suggests that VC wio|uld in turn be degraded into carbon dioxide. All three groups mention that bactelria might be used to decontaminate groundwater polluted by spills of solvents like PERC and TCE. It is worth noting here that the process of VC degra d.ation to carbon dioxide and presumably HC1, requires further investigation This step may not occur at all, or it may be extremely slow. In this light, or e study reports that over the 17-day experimental period, the VC concentrateon remained virtually constant [ 4 ]. If degradation was not significant, the tie|chnique would not be safe. We would be faced with a situation where biodegr^dation of toxic animal carcinogens PERC and TCE - leads to production of a more dangerous substance, VC - an established human carcinogen. Chemical transformation A second potential origin for the VC found in groundwater and soil is for- nation through chemical reaction. One possibility is hydrolysis of the com monly used solvents with water or base substitution of chlorine. This reaction would be more favored in a basic rather than an acidic environment and would result in the formation of products contabining oxygen - not in products like DCE or VC. Since these products have not been identified, the reaction is probably not favored. Indeed, there is evidence that hydrolysis of the three solvents is very slow [ 20 ]. A second possibility is that the VC and DCE found at various sites could be formed by a chemical reaction that remov as both a chlorine and hydrogen atom (dehydrochlorination). The top two reactions depicted in Fig. 2 show how VC can be formed through dehydrochlorination of two different starting products - 1,1-DCA and 1,2-DCA. Figure 3 shows four separate dehydrochlorination reactions that can lead to the formation of the three DCEs. The two starting chemicals in this case are 1,1,1-TCA and 1,1,2-TCA. A third possibility is that VC is formed Ithrough a dechlorination reaction in which a chlorine molecule is removed. This process is depicted in the two bot tom reactions in Fig. 2 which show forma :ion of VC through dechlorination of 1,1,1-TCA and 1,1,2-TCA. There are similar reactions for the formation of DCE from dechlorination of ethanes containing four chlorine atoms. Such chemicals are not widely used, however, fxcept as intermediates and for sim plicity, we do not examine them further. In the Santa Clara Valley, the chemicals appearing in Figs. 2 and 3 were found in the groundwater and in the soil near many firms in the area at the concentrations indicated in Table 4 [1 ]. In reference to the table, recall that VC can be formed from DCA or TCA and that DCE can be formed from TCA. } 5 l f. SPI-00008 170 1, l*4idilorMtFun> 1,1-OCA Cl H ci--i--i-H 1A -*C1 <11 1.2-didilorovtham 1.2-OCA 1,1, l-tnchlorotha TCA Cl Cl UJ-* HH Cl H Cl-i--i-H u 1 -tci (2) -Cl 2 13) 1.1.2-tridilorwtfurt 1.1.2-TCA Cl Cl -Cl 2 (4) HH )OCt Cl H vinyl cMoridt VC Fig. 2. Paths for VC formation. At the Ford Motor Co., the VC found in the groundwater could have been formed either from dehydrochlorination of DCA or dechlorination of 1,1,1TCA. DCA, like VC was found in the groundwater whereas 1,1,1-TCA was found only in tie soil. The trans- 1,2-DCE found at the site could not have been 1,1, l-tricftlorc*than* 1, 1-TCA Cl H Cl~^-- i, A 1,1,2~tneMorothrw l, 1,2-TCA Cl Cl Cl-- -HCl (5) -HCI (6) Cl H 4 >C=C( Cl K 1,l-d!Cftlorofthylfw 1,1-DCE l* l,2"tP\chloro*th*ft 1,1,2-TCA Cl Cl cJJ- AA 4C1 (71 1, l,2-tPichloro#thar 1,1,2-TCA Cl Cl Cl-iJAA -fCl IB) Fig. 3. Paths for DC E formation. Cl Cl Ci*-l,2-OicTiloro*thylen* 1 >CC( i-l,2-DCE HH Cl H > >C-C< trir>*-i,2-dicMciro*tfiyltn# tr*n*-l,2-DCE H Cl SP1-00009 i 171 TABLE 4 Contamination levels at sites in the Santa Claja Valley Site Chemical Concentration (ppb) Ford Motor Corp Milpitas DCA* trans- 1,2-DC E 1,1,1-TCA VC Groundwater <100 50 to 100 50 to 100 Soil <100 Great Western Chem. Co. Milpitas DCA* 1,1-DCA DCE" 1,1-DCE 1,1,1-TCA > 1000 100 to 500 > 1000 <100 > 1000 >1000 Intel Corp. - DCA* <100 Mountain View DCE6 100 to 500 trans-1,2-DC E >1000 <100 1,1,1-TCA 100 to 500 in VC 100 to 500 1- Sunnyvale Intersil 1,1-DCE <100 is trans-1,2-DC E >1000 n 1,1,1-TCA <100 VC <100 Source: White Paper [ 1 ]. `Not specified if this chemical is 1,1-DCA or 1,5 -DCA. "'Not specified if this chemical is 1,1-DCE or 1,5 -DCE. formed from either DCA by dehydrogenation or 1,1,1-TCA by transformation to 1,1,2-TCA and subsequent dehydrochlorination (see Fig. 3). At the Great Western Chemical Co , no VC was identified. An unspecified DCE and 1,1-DCE were found at concentrations greater than 1,000 parts per billion (ppb) in the groundwater an i soil, respectively. The only product detected that could lead to the formation of the DCEs is 1,1,1-TCA which was measured only in the soil at a concentration greater than 1,000 ppb. The chemicals found near the Intel Corp. site include DCE, DCA, VC, and 1,1,1-TCA. VC, found at 100 to 500 ppb in the groundwater, could have been formed from the dehydrochlorination Df DCA, detected at less than 100 ppb, or from the dechlorination of 1,1,1-TC',A, found at between 100 and 500 ppb. The trans-1,2,-DCE could not have been formed from the detected products without transformation of 1,1,1-TCA to 1,1,2-TCA occurring first. The unspecified DCE, found in the groundwater at between 100 to 500 ppb is prob- f t SPI-00010 ably 1,1-DCA which could have been formed from the dehydrochlorination of 1,1,1-TCA fcund at the same concentration. At the Intersil site, the VC detected in the groundwater at a concentration less than 10(1 ppb, could have been formed through dechlorination of 1,1,1TCA found i 1 the soil. The trans-1,2-DCE could not be formed directly from 1,1,1-TCA bi t the 1,1-DCE could - through dehydrochlorination. The fact that the correct combinations of the chlorinated chemicals were found together at various sites suggests that the chemical reactions in Figs. 2 and 3 could b<; taking place. However, it is true as well that TCE was also found at each of the four sites. This supports the possibility that biotransformation of TCE may actually be the mechanism leading to formation of 1,1-DCE and ultimately VC as described in Fig. 1. To investigate further the likelihood that chemical reaction may be the mechanism ol origin, we calculated the enthalpy of the reactions in Figs. 2 and 3. In each case, we determined the enthalpy of formation for each species in the reaction a] id the enthalpy for the reaction as a whole. Table 5 displays these data. It should be noted that this thermodynamic analysis does not indicate how long it tares for a product to be formed or detected. In the last column of Table 5, a positive enthalpy value indicates that the theoretical reaction pathway is endothermic - that it requires energy to take place; a negat ve enthalpy value indicates that the reaction is exothermic that it could cccur spontaneously assuming there are no kinetic or entropic barriers. The more negative is the enthalpy, the more likely the reaction will occur. From the values, we observe that none of the reactions involving VC formation is favored. In fact, the enthalpies of reaction are quite high. At the same time, we note that the reactions involving aqueous rather than gaseous HC1 are favored (less positive enthalpy of reaction) and that dehydrochlori nation is favored over dechlorination. The reactants in reaction numbers 1 and 2 - 1,1-DCA and 1,2-DCA - are undoubtedly in the liquid state in the environ ment. Because we have no data on liquid enthalpies, we present only the enthalpies of the gaseous state. We can surmise from the other table entries, however, that the enthalpies of the total reaction would be more positive or even less favond if the reactants were in the lqiuid state. We also note that in the environment, the HC1 is likely to be in aqueous form. Those reactions where this is the case are favored over those where HC1 is a gas. Some of the reactions in Table 5 that lead to the formation of one of the DCE products could occur spontaneously. These reactions are presented in more detail in tae tables of the Appendix. As we discussed above, in the envi ronment, the reactant and product both are likely to be in liquid form and the HC1 is probably aqueous. Under these circumsntances, the enthalpy of the reaction that forms, 1,1-DCE is -3.32 keal/mol (see last number in column under 1,1-DCE in Table A-3 of the Appendix); that forms cis-1,2-DCE is --4.02 keal/mol (see last number in column under d.v-L,2-DCE in Table A-4 of the SPl-00011 ZtOOO'ldS T ' r $ Xs >= B , "S. v"> 0_9 s 33 0"0 = --- s h rC <q 5? 5' =' -&&2 '2ft# Jff3tt tt ciStB* !'' gO sfrt*i "o* o *2ft _ y Cft 3w < -= = c- 3 3 sz. 5ft1 fwt t* s t 3- <-* S'! S8 ' J o < ff f? 3 o > o o > i 3ft r Kft SSr - (t ft w 2; o0 _3 3* II -o3 > - -Oo4. of2-qtT. Do -3 o> .1 |3 o 3 s: S -"=r ii ii U CO >U 05 &5 N U tO 05 tO 05 Ij L gM ii -n3 > i i , c o |5 . i? 5 3* 38- 3 *0 AO) .rotI ^<uoI,rrooI*teoINf9oI<foeI .t!ko> .OIU NNISO JOI*- NNISS bto o<0 otO b(D X o s 5: S- f0rt* 5O3Q' 2o Z 3 . ` -3 a ttn e n 0 vc 0 vi #n #n o b ?* -gz >o < o .5.5 r?0- <^to3 C5- Wi ^f3* 5* S ! O S' ft ^ ft "O 05 O 05 0 o u o O' I I I I ,*~-- <JQ ~ A 05 o -o * a rna I *cr L 0er II I oo P3 O~ oS c* ^ tn . to -m - 05 cr bno - b '* b boc o-- 0-0 *--_ ft IT o NO o bb - 02 -- - ZLl i Enthalpy values for chemical transformation F s I 0 3 3 9 U P 9t P U P: 0 9. U. -1 u JC The speed vith which reactants form products cannot be deduced from the reaction enthalpy. Another factor that can influence the formation of products is the kinetic quantity - the activation energy barrier*. A pictorial represen tation of sucli a barrier is shown in Fig. 4. In this particular situation, the energy of the products is greater than the energy of the reactants indicating a net energy requirement. The products are higher in energy than the reactants Reaction rates f re proportional to reaction rate constants which are inversely proportional to the exponential of the activation energy. SPl-00013 j j 175 by only a small amount - E0 in Fig. 4. To get the reaction to move in the direction of the products, however, a muo:h higher energy, one equal in magnitude to the activation energy, is necessary. The fact that a reaction theoretically could occur spontaneously according to its enthalpy value may not imply that the reaction occurs in practice. If the particular reaction has a high activation barrier, it will probably not occur. No data on the activation barrier for reaction 1 in Fig. 2 appear to be available. Although reaction 2 in Fig. 2 has been studied [ 22,23 ], no value for the height of the barrier has been established. Data on the barriers for reaction 3 in Fig. 2 and reaction 5 in Fig. 3 involving 1,1,1-TCA are available. The height of the activation barriers for the dehydrochlorination reaction, number 5, is 54 heal greater than the enthalpy of the reactant - 1,1,1-TCA. The barrier for the dechlorination reaction, number 3, is even higher, at an estimated 92 keal. Thii i suggests that significant additional energy would be required for the reactions to take place. Although we have no information on the barrier height of reactions involving 1,1,2-TCA, we doubt that it would be significantly lower than that of 1,1,1-TCA. Factors that may favor the reactions incli.de the presence of catalyzing agents like the microorganisms and high temperatures. Indeed, the high temperatures found in landfills result from anaerobic biodegradation processes of thermophile bacteria which flourish at 120-1403 F (49-60 C). Bacterial catalysis could lower the activation energy so that detectable amounts of product would be formed. Thus, even with high activation barriers, we cannot rule out chemical reaction as the mechanism for transformation. Migration from PVC A third possible origin of VC is its migrat ion from PVC - the so-called "Milk Carton Theory." In sanitary landfills, PVC in numerous forms would be expected to be present. These would indue,e food packaging, bottles, and dis carded piping and siding. Near leaking underground storage tanks, it is less obvious that PVC would be present. PVC pipe, however, has been used in water distribution systems all over the country and could be the origin of the VC found in Santa Clara Valley. In polyvinyl chloride products, some vinyl chloride is retained within the network of the polymer as a residue from the polymerization reaction. This residue may eventually leave the polymerized material by volatilization or migration. One group has been studying VC migration in PVC pipe containing 29.5 ppm of VC [25]. When they prevented volatilization and increased the surface area of the pipe wall in contact with the water, they found that VC migrated into water at levels greater than 50 ppm. With chlorine present in the water, the VC reacted to yield products containing oxygen like chloracetaldehyde and chloroacetic acid. In groundwater or under soil, only small anmount of volatilization from PVC i ! I i ! | SPI-00014 products might be expected to occur. But under normal circumstances, we might expect VC to migrate mainly into the surrounding media. Ando and Sayato [25] invelitigated pipes which are rigid and had reasonably thick walls. Significant ml:igration from other types of pipe with thermal walls might be possible. In ndfills, where more flexible PVC products may have been placed, VC migratton would probably be lower [ 10 ]. Depolymerization of PVC Under curtain conditions the PVC can decompose to form VC molecule. In general, this requires either significant thermal energy or ultraviolet irradia tion. It is unlikely that the high temperature required could be achieved or that sunlight would penetrate at sanitary landfills or groundwater. Disposal of aerosol cans As mentioned in an earlier section, the use of VC as a propellant in aerosol consumer products was banned in 1974. Before that time, aerosol cans con taining a "heel" of VC were probably widely disposed of in sanitary landfills across the country. The VC would eventually leak from the cans as they are crushed or corrode and it would be detected in the gas collection system. Although this source of VC may adequately explain detection of the chemical at sanitary landfills, it does not explain detection of VC near underground storage tanks or in aquifers located near chemical spills. It also does not explain the origin of the DCE detected in either location. Contamination of solvents One other potential source of the VC is as a contaminant from the produc tion process of chlorinated solvents. Under such circumstances, we would expect to detect small amounts of VC and, perhaps, DCE, as well, in much larger amounts of the solvents in the environment. The data of Table 4 do not allow us to draw a definitive conclusion. Some TCA is produced from VC, and the distillation vent gas from a model plant contains 0.1 percent of VC by weight. The gas from a drying column vent in a plant pioducing PERC and TCE contains 21 and 16 percent of VC and 1,1-DCE by weight, respectively [26]. These data suggest that VC and 1,1DCE may be present in small amounts in virgin TCA, PERC, and TCE when they are sold. Because of a lack of specific information on the concentrations of all species present at landfills and at spill sites, it is not possible to decide whether the detected VC and 1,1-DCE are simply contaminants in the widely used solvents. Such data co jld help shed light on the VC origin. V. Results and conclusions Vinyl chlor de and dichloroethvlene have been found at sites where the widely used chlorinated solvents - TCA, PERC, and TCE - have been released into SPI-00015 177 tr.e soii and groundwater. Vinyl chloride has also been detected in the gas streams emitted from sanitary landfills. Both vinyl chloride and dichloroethyiene are used only as intermediates in the production of other chemicals so it is unlikely that either chemical was disposed of or used in the vicinity of the sites of detection. A number of investigators have demonstrated that VC and DCE are formed in the laboratory through anaerobic transformation of TCE or PERC by microorganisms. This mechanism is a possible explanation for the origin of VC and DCE. More research is required for verification of this formation mechanism. Our analysis suggests that another pathway - chemical reaction - may also be responsible for the formation of VC and DCE. In this case, the reactants that are converted to VC and DCE through dehydrochlorination and dechlorination include DCA and TCA. Although DCA's primary use is as an intermediate in chemical production processes,T' CA is a widely used solvent. The results show that the formation of DCE is more favorable than that of VC. More research is necessary to determine whether or not this pathway is likely. Another possible explanation for the presence of VC and DCE are that they exist as contaminants in chlorinated solver ts. VC may also be present because of migration from various plastic products, depolymerization of those same products, or leakage from aerosol cans. The intent of this paper was not to assign a definitive source to the hazard ous chemicals. Its purpose, rather, was to propose a range of possible sources as the starting point for more detailed investi gation. In the future, it will become increasingly important to verify the sources - particularly of VC, an estab lished human carcinogen. As time passes, more VC may be formed, and the air and groundwater will become increasingly piolluted. If we can identify the ori gin, we can hope to prevent or limit its form ation with more certainty. References 1 White Paper, Groundwater and drinking water in ::he Santa Clara Valley, California Department of Health Services, October 5, 1984. 2 K. Hinman, D. Schwartz. E. Soffer, D. Morell ar.d F. Reinhardt, Santa Clara Valley inte grated environmental management project: draft stage one report, October 11, 1985. 3 Comments on Integrated Environmental Management Project. March 14, 1986. 4 AWWA Research Foundation, Occurrence and removal of volatile organic chemicals from drinking water, undated. 5 P.R. Wood, R.F, Lang and LL. Payan, Anaerobic transformation, transport, and removal of volatile organics in groundwater, in C.H. Ward, W. Giger and P.L. McCarty (Eds.), Groundwater Quality, Wiley and Sons, 1985. p. 493. 6 California Air Resources Board (CARB). An assessment of the volatile and toxic organic emissions from hazardous waste disposal in Califoinnia. February 11,1982. Chemical Marketing Reporter (CMR), Vinyl chloride chemical profile, June 2, 1986, t' I i i I SPI-00016 178 8 Chemi :al Marketing Reporter (CMR), Polyvinyl chloride chemical profile, June 9, 1986. 9 Chemi :al Marketing Reporter (CMR), VCM aerosol marketing ban proposed by U.S. safety unit; ir ventory trace also planned, May 27, 1974. 10 D. Dor iger. Toxic substances control, a case study of vinyl chloride. In: Resources for the Future, Johns Hopkins University Press, 1978. 11 OSHA smergency temporary standard for exposure to vinyl chloride, Fed. Regist. 39, (1974) 12342. 12 C. Mali oni and G. Lefemine, Carcinogenicity bioassays of vinyl chloride: current results, Ann. N Y. Acad. Sci., 24 (1975) 195. 13 Environmental Health Perspectives (EHP), Vinyl chloride related compounds, Vol. 21, Deceml er 1977. 14 U.S. De Jartment of Health and Human Services, National toxicology program (NTP), Third annual: eport on carcinogens. December 1982. 15 K. Woii and T.W. Chesnutt, Chlorinated solvents: market interactions and regulation, J. Hazard; us Materials, 15 (1987 ) 000-000. 16 U.S. Intemational Trade Commission Reports (U.S. ITC), Synthetic Organic Chemicals, U.S. Prc duction and Sales, 1984. 17 Chemicr 1 Marketing Reporter (CMR), Chemical profile, trichloroethylene, January 27,1986; Februar' 14,1983. 18 F. Parsois, P.R. Wood and J. DeMarco, Transformations of tetrachloroethene and trichlo- roethene in microcosms and groundwater, J. Amer. Water Works Assoc., 76 (1984) 56. 19 P.L. McCarty, Application of biological transformations in groundwater, In: N.W. Durham and A.E Redelfs (Eds.), Proceedings Second International Conference on Groundwater Quality Research, 1985, p. 6. 20 U.S. Environmental Protection Agency (EPA), Treatability Manual, Vol. I, Treatability Data, September 1981. 21 D. R. Stu 1, E.F. Westrum, Jr. and G.C. Sinke, The Chemical Thermodynamics of Organic Compounds, Wiley and Sons, Inc., 1969. 22 Z. Czarny, B. Malinowska and J. Banak-Tabkowska, Pol. J. Chem., 41 (1967) 1583. 23 B. Malinowska, A. Malik and Z. Czarny, Analysis of the kinetic data obtained from the reac tion of eliminating hydrogen chloride from 1,2-dichloroethane, Pol. J. Chem., 49 (1975) 2061. 24 A.S. Sudlio, P.A. Schulz, Y.R. Shen and Y.L. Lee, Three and four center elimination of HC1 in the mcltiphoton dissociation of halogenated hydrocarbons, J. Chem. Phys. (1978) 2312. 25 M. Ando snd Y. Sayato, Studies on vinyl chloride migrating into drinking water from poly vinyl chic ride pipe and reaction between vinyl chloride and chlorine. Water Res., 18 (1984) 315. 26 U.S. Env:ronmental Protection Agency (EPA), Organic Chemical Manufacturing, Vol. 8, Selected Processes, Office of Air Quality Planning and Standards. Research Triangle Park. Decembei 1980. SPI-00017 ) i 6. ifeiy the 74) alts. 21. bird i, J. :als, 186: hloam ater lity .nic ac61. iCI 12. . 8. rk. 9 72 "c2 41 a3-* c= J> >v >s .ff 0 1 o ao uo I .st a: S ^w 41 TJ jWc J52 J^S J o i! >o aoC*5 'T Of a ; s lI a> 2s c= >5 a .2 "O 5 oQ< os x' "- xw X- Ui JX TM =5 5- o- x oo X < if = Ed .2 s 1*1 c CJ w c Oo 'i d^ XX \o/ o /\ xx !l ao cm CO mm i be O 41 4} 53 1s 4> sa :s 24*>a1*t XJbre 0 pB _Q_. Oto w n zcmr Qc o --* o " S5 41 _ 45 3 41 C/3 5 1P oto> i -o J= 4 V C *3 C S- C ". 4u1 l2: cj 4> C 4) 5 .2 - 8o ^< .c 13| g.s i S' -2 | Jo Z5 j_ws wc 41. -.Se*. -3 4) _^C- *3 e`Cqj *-2P" C X41i i be "3 X II! O ~w-- oCdOi c9r' i .2 c S 7. tS 179 1 i * * i * i SPI-00018 T 180 Enthalpy of formation of vinyl chloride (VC ) from 1,2-dichloroethane (1,2DCA ) at standard temperature and pressure from standard enthalpies o f formation---------- --------------------------------------------------------------------(S TP ) t i o n U r a l / m n lAH, kcal/mol Dechlorina AH2 (STP) Cc 31 > 11 >o <| CCJ O _-c X1 g 1 CJI X CXJ r II SI \/ C1J CJ _/ \ CJ X _ C- U-X U- O-X 05 9 00 U5 1 05 05 00 co -- iorot 05 CO ci t/5 CM ~ o* Ooto'! jy4c) >% X 4) H H \/ C1J CJ /\ XX O Il 05 CM 99 CM bo CCOO to 0000 CM 1 CM ChOM &C c i o CrO- G 0 d SPI-00019 Notes: see notes of Table A - 1. Appendix 181 In this Appendix, we show the complete details of our enthalpy calculations, All calculations were performed acco:riing to the relationship: 4-^reac -- PRODUCTS -- Xd/fjREACT. (NTS (A-l) Table A-l describes the enthalpy relationships in the dehydrochlorination of 1,1-DCA to form VC. We also show ;he enthalpies for the second stage reac tions that form acetylene and ethylem i. The enthalpies for the formation of VC from 1,2-DCA are shown in Table A-2. We again present enthalpies for tb e second stage reactions leading to acet ylene and ethylene. In Table A-3, we show the enthalpy relationships for conversion of 1,1,1TCA to 1,1-DCE and VC. We also show) similar data for the further conversion to acetylene. TABLE A-3 Enthalpy of formation of vinyl chloride {VC) from 1.1.1trichloroethane (1.1,1-TCA) at standard temperature and pressui from standard enthalpies of formation dtf, kcal/mol (STP) Dechlorination JH. 9JHvt kcal/mol (STP) 1.1,1-TCA 1,1.1 - trichloroethane methyl chloroform 1.1-DCE 1.1-dichloroethyi: vinylidene chlorii de acetylene ethyne 9* Cl-Cl -Ct -H Cl H - HC1 j b.p. (SC, 14.1 760 mmHg); (-33.10(g)) -22.09 <g) JHt: (-33.10(g)) -40.02 (aq) ( -33.10 (g)) -22.09 (g) ( -33.10 <g)> -40.02 (aq) t -- 42.7 U -22.09 (gi ( -42.7 (D) - 40.02 | aq) ( -42.7 M )) -22.09 (g) ( -42.7 (b -40.02 (aq) b.p.oc, 760 mmHg): (-33.10 lg)) JH.: (-42.7(1) Notes: see notes Tuble A-l. 0(k) 0(b) Cl H CLC'C'h 37 (32) 0.30 (g) 0.30 (g) -6.0 (1) -6.0 (1) 0.30 (g) 0.30 (g) -6.0 (I) -6.0 (1) vinyl chloride chloroethyiene Cl H H C-C. H -13.37 8.4 (j) 8.4(*) - cv- H-C-C-H (11.31) -6.62) (5.01 > - 12.92) (20.91) (2.98) (14.61) -3.32) 0 (g) 0 (gl -84.0 54.19 (g) 53.89 54.19 (g) 60.19 - HC1 H-C-C-H 141.5) (51.1) -84.0 -22.09 1 g) 54.19(g) -40.02(g) 23.7 5.77 (65.20 (47.27 (65.20) (47.27) (74.30) (56.87) (75.80' (56.87 (65.2) (56.9) V SPI-00020 T "t T 182 NNNNI 5 -M55 J^H C> >nX ocI I90 V XcsU4t * :|S : 3 co r9t0Ogtfin < HCJ 4> !6 j 2 auQi1o--cg2w -.*6-8 X0oN1 ? ^^OrC-J<9Be0fol >0Mcb_o<--doL0oU0r<tboeoA"w > o <j " 11 11 CoIJ c-1.2-DCE cii-1,2 dichlorocthylene 1.1,2-TCA 1,1.2-trichloruethane -OC52d *5usao >s 4 O3 . *9 iI < w.c&j >a*> "a9g IIli11 W 9( U UA ^ A -- --oo-- o--'p*'-'r,*^r'*,,'cw- ciririHwwwN tII1II1! d^ SPI-0002A OCMrC-MOCPMr-C'OMaroc-cbOo^c*of"ao- $^C0^P-`OP*>rt o p r- p- N N O CO X op <*b0 P- P"*- cifbl P <ob 183 CM con u<ob c~ C*j *b 0O1 UOI <*-f<7lpbn^-<*"cWp*5o?O-pairct>**-5oN^ - I 7^ - I O-- CM cm rj eosj O-- ao (0 u--j 2T} 0 40 '">. Q0 40 *" ` Xri'IeInril ,l ao 2 * C< -oc JSi XO vo\i/ /\ OX /5 w C- Sx x 3 -2? c"oI' -- ^ ** <^1eI c*11t j y_>.v=> -sVt555rw/o\\\1/ CM O cm II ' esi v '"T "" N fi eg fi *? i C<OoI ceOoI CcaOI Orc-ird-.rp-i.f- 40 40 o Oft c o p. c an* SPI-00022 184 The enthalpies for the reaction of 1,1,2-TCA to form 1,1-DCE, trans-1,2DCE and cis- 1,2-DCE are presented in Table A-4. Values for the conversion to acetylene are also exhibited. The values illustrate that the formation of DCE (negative values for the enthalpy of reaction I is more likely to occur than is formation of VC (positive values for the enthalpy of rection). However, certain factors explained in the main text may increase the likelihood of both reactions. We note that the enthalpies of the reactions for the second stage conversion into ethylene or acetylene are always highly endothermic indicating that they probably do not proceed spontaneously. )j SPI-00023 T