Document qad83or6yek6QyVy12yzR3EoR

Vinyl Chloride: Inhalation Teratology Study in Mice, Rats and Rabbits by J. A. John,* F. A. Smith* and B. A. Schwetz* These studies evuluiited I ho effects of inhaled vinyl rhlorido monomer i Y(*M> on mmi*e. ral and rabbit embryonal and fetal development, (iroups of pregnant (T'-l mire. Spnigue-lkiwlvy rats and New Zealand white rabbit* were exposed to 7tMl ppm V('M Tir 7 hr daily during the period of major organogenesis. Subsequently, other groups of mire Here similarly exposed to Til) ppm VCM. and rats and rabbits were exposed to 2.70(1 ppm. While maternal toxicity was observed, exposure to VCM did not cause significant embryonal or fetal toxicity and was not teratogenic in any of the three species at the concentrations tested. Simultaneous exposure or some of the pregnant animals to Vl'.M by inhalation plus 17% ethanol in the drinking water resulted in toxic effects greater than those associated with exposure to VCM alone in the three specie*. The fetal effects observed were similar to those reported for these three species following administration of ethanol without YOU exposure. Introduction Inhalation exposure to vin.vl chloride monomer (VCM) has been shown to be cureinoj;cnic in laboratory animals (/, J) anil in humans </). The carcinogenic potential of inhaled VCM following in Htcru exposure has been reporlcd but observa tions to determine the teratogenic potential in laboratory animals were not made. Kpidemiolojric studies (i-d) of incidence rates for malformations of the central nervous system amonjr families of employees or residents in the vicinity of vinyl chloride polymcrixalion facilities have not supported any evidence that VCM is teratogenic in humans, A series of studies were conducted in our laboratory to assess the hazard associated with exposure and to investigate the mechanism by which VCM mijrht exert its toxic effects. The purpose of the studies described in this rc|xjrt was to assess the embryotoxic and teratogenic potential of inhaled VCM in mice, rats and rabbits. The exposure levels tested in the teratology studies are presented in Table 1. In an initial experiment, (groups of mice, rats and rabbits were exposed to olH) ppm of VCM, 7 hr daily on days li-l.j # Tux if flurry HvM-iirvh IjilHiratury, I {(-alt h :ihil Knvii-umm*ntal Sfii-nct'M t'SA. I>u\v Cht-mintl C.S.A., Miillaml. Mu-lii^'an -In.Iii. October 1981 (mice and rats) or (i-18 (rabbits) of gestation. Subsequently, additional groups of ruts and rabbits were exposed to 2f>()() ppm. Kor each concentration tested, concurrent control groups of mice, rats and rabbits were sham-exposed to filtered room air. Since previous studies in this laboratory indicated tlum the primary metabolic pathway for VCM is blocked by ethanol (.'), it was considered possible that simultaneous administration of ethanol in the drinking water of animals exposed to VCM mijrlu alter its metabolism in a manner which would enhance its toxic or teratogenic potential. Thus, in this experiment some of the VCSl-cxposcd animals were jriven 1.V* (v/v) ethanol in their drinking water during the same period of jrcstation. Tnlilv 1. Ti-rilUiluyy Mudirx with vin.vl rhlurjdi': li-vvl. uf Miw Kilt?', r;ihltii^ Min*. ral>, t*:tUliU," VCM ciiiivii. I'pm .'ll HI 74 HI .">41 7*1 2.r*4s> J.Too 74*1 0 Klhiitf.l vunvn, 0 ir. It i'. It i`> 0 It 171 fH !' \L u.i. The Ifi-sitotrfiiif potential of imbibed ethanol in mice, nits, anil rabbits was previously studied in our laboratory and reported by Schweiz ot al. (s'). No teratogenic effects were observed when 1-V-! ethanol was yiven in the drinkiny water to mice and rats on days (M5 of gestation or to rabbits on days (MS of yestation, although retarded fetal growth and development were observed in mice and rats. Methods Female CF-1 mice (Carworth, 1'nrtaye. Michi-' yan) weiyhiny 25 to :{() y, Sprayiio-Dawlev rats (Spartan Research Animals, Inc., Hasletl. Michiyan) weiyhiny approximately 250 y and New Zea land white rabbits (I.anyshaws Rabbit rv, Auyusta, Michiyan) weiyhiny 5.5-1.5 ky were used in this study. The day on which a vayinal pluy was observed or the day on which sperm were seen in a vayinal smear was considered day zero of preynancy for mice and rats, respectively. The day of natural mutiny was considered day zero for rabbits. Between daily exposures, animals were housed in wire-bottom cuyes in a room controlled for temper ature, humidity and liyhl cycle. Commercial labora tory animal food (Ralston Purina Co., St. l.ouis. Missouri) and tap water or lap water containiny ethanol were available duriny tile periods between exposure to VC.M. Food consumption was mea sured til 5-day intervals for mice and nils and at 2-day intervals for rabbits. All animals were de prived of food and water duriny the 7-lir exposure period each day. Kxposurc of bred animals was conducted in stainless steel chambers of 5.7 m:i volume under dynamic conditions. The atmosphere of VCM was yenerated by dilutiny yuseous VCM with filtered room air at a rale calculated to yive the desired concentration. Vinyl chloride monomer Ichloroothylene) obtained from Malhesnn lias Products, .Joliet. Illinois was used for the exposures. Tile actual concentration was measured with an infrared spec trophotometer (Perkin Kinier I2A or .Miran J> with a multipath yas cell. All animals wen.* observed daily throuyhout preynancy and maternal body wciylits were recorded at several intervals duriny yestation. Preynant mice and rats were sacrificed by carbon dioxide inhala tion on day IS and 21 of yestation. respectively. Preynant rabbits were sacrificed on day 2!> of yestation. The uterine horns were exteriorized limuiyh a midline incision in the abdominal wall and the number and position of live, dead and re.-orbed fetuses were noted. After beiny weiyhed, mea sured tcrown-rump leiiylh) and sexed (mice and rats), the fetuses were examined for external 172 anomalies. One-third of each litter was immediately examined for evidence of soft tissue anomalies by dissection under a low power microscope (.'/). The heads of those fetuses (mice and rats only) were preserved in Hoiiin's solution and examined for soft tissue but not skeletal anomalies <IH). Rabbit fe tuses were sexed on the basis of examination of internal yenilalia. All fetuses were (hen eviscerat ed, preserved in alcohol and sub,-.ei|Uenlly cleared and stained with Alizarin Red-S for examination for skeletal anomalies (II). The Fisher exact probability tot (/-') was used to evaluate the incidence of resorption.-- amouy litters. Maternal and fetal body wciyhts and body mea surements and maternal liver wciyhts were ana lyzed statistically, by an analysis of variance and Donnell's lest (/.(). The incidence of fetal anomalies was analyzed by the Wilcoxon lest as modified by Haseman and Hocl (/.J). The yroup of animals which was exposed only to vinyl chloride .served as the control Ibr those animals which were exposed to vinyl chloride in combination with 15') ethanol in the drinkiny water. The controls for animals ex posed to vinyl chloride and maintained on tap w ater without ethanol wore exposed to tillered room air in exposure chambers which were similar to those used for exposure to vinyl chloride. Results and Discussion Maternal Toxicity Fxposurc to 5(ltl ppm VCM was maternally toxic to mice: deaths (5 of 2!) bred females), decreases in the amount of weiyht yained duriny yestation, in food consumption and in absolute liver weiyht a.compared to the air only controls were observed. Kvidenee of toxicity was not apparent amony mice exposed to 5b ppm of VCM. The combination of VCM exposure with I5'i ethanol in the drinkiny water siyniticanlly enhanced the toxicity as com pared to VCM aloiu- Ibr both concentrations, thouyh no deaths occurred in the 5u ppm VCM plus ethanol yroup of mice. Rats exposed to 500 ppm VCM yained less weiyht than emit rots duriny yestation. but no other evi dence of toxicity was observed at this level. One maternal death amony 17 bred feint ties, decreased food consumption and an increase m liver weiyht were observed tit 2.5ou ppm VCM in rats. F.thauol yiven in combination with 2501) ppm VCM was more maternally toxic than exposure to VCM alone: the amount of body weiyht yained by preynant rats duriny yestation and Ibid consumption were siynilicanlly decreased in the yroup yiven the eombi- Knvimnmcnlnl Health Perspectives I 1 I'vi-w*... nation. The liver weight relative to body weight was increased in this jrroup as compared to the nits exposed only to VCM, lull no deaths were observed its a result of treatment with the combination. An ethanol jrroup was not included amonjr the rats exposed to 500 ppm of VCM. Some deaths were observed amonjr pregnant rab bits exposed to 2500 ppm VCM alone (one nl`seven bred females) or in combination with ethanol Cl of lit bred females); however, other evidence of toxic ity in rabbits consisted only of decreases in food consumption amonjr those exposed to 500 ppm VCM alone and amonjr rabbits jriven the combination of 2500 ppm plus ethanol in the drinking water, Amonjr mice, rats and rabbits jri veil 15'/< ethanol in the drinkinjr water durinjr jreslation. Schweiz et id, (.s') reported that maternal toxicity, us evidenced by decreased body weights, occurred in all three species. Observations at the Time of Cesarean Section Amonjr litters of mice exposed to 500 ppm of VCM. the incidence of resorptions was increased; IT.) of the implants were resorbed versus 7'.f in the concurrent air controls (Table 2). Historical control data from SOI litters of CS-1 mice in our laboratory show the mean perrontajre of implantations resorbed to be II'/) with a ranjre of (!-22'.f. Thus, both of these values are within the ranjre observed for control jrrnups of litis strain. I.illcr size and fetal body woijrht were decreased at 500 ppm. These effects may have been secondary to the toxicity obser ed amonjr projrnanl dams at this exposure level Toxic effects on the embryo or fetus were not observed amonjr litters of mice exposed to 50 ppm VCM. Kthanol in combination with VCM produced jrrealer fetotoxicity than exposure to VCM alone at both levels. In the 500 ppm VCM plus ethanol jrroup, a decrease in the percenlajre of prejrnant mice was observed. This resulted in only seven litters, two of which contained only implantations which were re sorbed. l-'elal body measurements were decreased amonjr the ethanol jrrotips when compared to jrroups jriven either 50 or 500 ppm VCM alone. No adverse effects on the percenlajre of prejrnant dams or the incidence of implantations resorbed were observed amonjr rats (Table ;{). Kxposure to R&S 021459 Tuble 2. Mice: observation* al the time of cesarean section. No wm. no ethanol ;h |i|im VCM lln ethaniil I.VI ethanol NoVCM. mi ethanol .`INI ;>l>in VCM no ethanol l.Vi ethanol Nmnlier uf litters l.ivc fetuses litter* M Implantations i-esuriied Fetal body weight, jr* Fetal crown-rump lenjflh, nun" 'i I'repianey 21 1(1 - 1 I.'i(-|(l2lin 1,00 i. 0.11 22.0 l.ii XTcJI :(Ti Jo 1! -.1 NlSItfS) 1.112 - II. 1(1 21.2 u.s" 71(20 27) in HI 1 llil'.i 172) o>.i _ n.ir ITJ.-I - l.-V 2d 12 : 2 7(2*i 2.7 li 1.07 _* O.IMi 22.7 .- 1.2 N-djS :(2j IH 11 2'* 12(22 2IM1' II.HH - ((.It1, 2:{.(i 1.0 72(21 2:0 7 s - IV is hi (i;o U.7> - II. 1.7 21.2 . l.-V :II(!I2!I)*' "Mean * S.I). '`Significantly different from :iir-e.\|nsi'<| control, /> . O.ti.Y ^Significantly different from VO!'0\jNscd gnmp. /< o.u">. Table II.. Hals: observations at the time of cesarean section. Nuinlier of litters Live fetuses Inter* implantations resoi'lied Fetal IhhIv weight. JT* Fetal crown-rump lonrth, mm" '4 I'rejrnaney No VCM. no ethnnol 2S 12 - 2 H I 2-12) .`i.r.7 o.2'i VdA\ l 1/J !H1(2K2H> .`shi ppm VCM. no etliiinol 21 p> . > 2111 ;i!isi .`i.M n.:is1. 12.11 o.S1, OlCtl XU 51Mean ? S.I), ''Signilicanily different from nir*cX|H>sc<l control, /> n .'), 'Significantly different from WMvximsed group. / October 1981 No WM. no elhatHil 1!) i;i * 'I -Y.V.i o.;j? i.i.c - i.;. iCMioutn No ethannl Hi t:t * 'J :*o; 23 o a.(12 II.2H vx:\ - u 1011(17 171 ppm VC.M l.Vi ethanol Hi 12 2 117 l!Cn :>.:n - ".22* 12.1 o.!r alt Hi 171 25(Hl ppm \'CM plus ethanol resulted in fetal body weights and crown-rump lenjfths which were lower than fetal body measurements aiming litters from rats exposed only to 25(H) ppm VCM. In the jjroup exposed to 5(H) ppm of VCM alone, fetal body weights were decreased as compared to concurrent air controls, thoujrh fetal crown-rump lengths were sitfiiilicantly increased. In rabbits, the incidence of resorptions was significantly increased unions litters jdven 25(H) ppm VCM plus ethanol, where 5-'W of the implantations showed evidence of resorption versus 21'* union): Tabic I. Itahhits: observation* sit the linicnf cesarean *c<tbm. Number of litters I.ivr fi'lu.'cs litlcr1 S Implantations resorliod Fetal (totiv weight, g*` Kcial uroim-rump length, mm** I'rvirnanrr No W.M. n<> ethanol IS >* I lido m*) :e,.i( i.s* Pl.O 1* IIHNlS 1m ppni Vt'M, no ethanol ip T 21' Sill IV11 :< 1. >:< 1.17 aj.n .`i.n i.V I! Jto No Vf.M. no ethanol ii r :t 22(1PSM .'id, 10 * 1>L* i.7 Inin 11 Ih ;*Vin pptn V(*M No ethanol . i; t i 2 a in il'i 77 l. (s IV#' elhatioi m t i Vi( 7P | IP)' a*, is .i.ss fcT,l * -VJ 7* >7.7 ' !M 1* I3*i **.Menn t S.l), ``Significantly different from air-eX|M?.rd control. p n u,"i. `Significantly different fnun V('M*e\po?.eil group, ft n.n.V KMitiuiI examination Soft tissue examination Skeletal examination Hones of the skull Tabic V-\. Mice; incidence of JVlaJ anomalies. No Vf.M. no ethai oj No. fetuses too. llttel'M examined VI ppm Vt'M No ethafio) IV# ethanol No V<\\1, no ethanol Vki |i|iin Vt'M No ethanol l.V; ethanol 2'2K2m 71(2(11 221(201 U7(2< 22iii2ii| 7V2(0 i^ucjo) MV2m IVtdli -UN l-li \y.u i ii tirii 111_ 1ii7i2Ci :i2V2'n 217(2i'ii 21V l!'l 7:KI Pi 21V l`.'i 112i mi Vito) .ViCo :t7(o) Table rh. Mia't incidence of fetal anomalies. No Vf.M. no ethanol *t frtU'O <# litters! affected .`iii ppm Vi '.M No etlianol l.V# ethanol No Vf.M, etlianol Vm ppm Vt'M No etlianol l.V# ethanol External examination Cleft palate Aiin|ithiilmia Kxeneephalv Soft tissue examination Thvmus Skeletal examination Skull lames, (infused Skull, delayed ossification Slernelirae, unfused Sternebrae, delayed ossification Vertelirae-iumliar spurs Vertebrae, forked alias Vertebrae, delayed ossification Him <1 <t 0 0 pcc.i :2( 7(Vl> ICCi) (i.lC.) It Kid) t: 0 u 0.7<o> NUT) :t(2."i) ICC.) vim Kim 0 "Significantly different from V(`M-exposcd ^nniji, jt u.OV `Significantly different from air*cx|nsed control, p * o,u.T 174 2(21) u It lt71 iMiVb" llll 1IHIIl.tioTv* IK limr' 2(21) ICIC.P Kill u II Km n K12< K'.iVli 2( I'.ii KI2) IMIi It 0 1(0) 0 mm 0 V2I i UlH.Vd1, Pt I2)1' (K IV')*' 2(21) 0 H r.t fit) 2(2m 0 1112m Tot Mm'1 IVlnm1-Ksm" lejm vim* Environmental Health Perspectives ft&S 021460 I I l I i 1i r ! those exposed onjy to VCM (Table 4). Only five litters were available for examination in the latter group. Litter size was decreased as compared to concurrent air controls among litters of rabbits exposed to the lower level of 500 ppm, but no effect on litter size resulted from exposure to 2500 ppm of VCM. The decreased mean litter size at 500 ppm most likely occurred because the rabbits in this group released fewer ova; the number of corpora lutea observed on the ovaries was lower among animals in this group. In the studies by Schweiz et al. (<Y), a slight increase in the incidence of resorptions was ob served among litters of rabbits, but not among litters of mice or rats given 15% ethanol in their drinking water during gestation. Decreases in fetal body measurements were observed by Schwetz et al. (8) among litters from both mice and rats main tained on drinking water containing ethanol. In the present study, decreases in fetal body measure ments were more pronounced when ethanol was given in combination with VCM in these two spe cies: however it is not clear if this apparent syner gistic effect was mediated via metabolic interfer ence in the maternal animal. Incidence of Fetal Anomalies Among litters of mice, no external or soft tissue anomalies were observed at a significantly higher incidence than the respective controls for any of the exposed groups (Table 5). Cleft palate was observed in 40%, or two of the five litters examined, at 500 ppm VCM plus 15% ethanol. This incidence is not statistically increased as compared to the group exposed to 500 ppm VCM alone. Due to the lowpercentage of pregnancy in the females, only five litters were available for examination in the 500 ppm VCM plus ethanol group. Among litters of mice exposed to 500 ppm VCM without ethanol in the drinking water, increased incidences of three skeletal variants indicative of delayed skeletal de velopment were observed. Ethanol, when given in combination with VCM, caused a significant increase in the occurrence of a number of these skeletal variants at both levels of VCM exposure. Thus, the occurrence of delayed skeletal development coin cided with those treatment regiments which were maternally toxic and resulted in decreased fetal body measurements. Among rats exposed to 2500 ppm of VCM. the Kxternal examination Soft tissue examination Skeletal examination Hones of the skull Thlr DA. Kats: incidence of fi'lnl anomalies. No VCM. no ethanol , *t(2X) l i:t(2s> :7<2si 22."><2S) ,\*n. fetuses dm. lilUM> I examined odd ppm VCM. no ethanol NoVCM. no ethanol 2-Hin ppm VCM Xf ethanol 1-V-i ethanol :ts7<:tli 1 ,,".)<at) Xs7(.'tl1 g.ViUU) 2-P< IP) 7(i(l!U 22!t< IP) !.->:(( l!l) 2iim;) 7:tt Id) 2 Ml Hi) Milliii ISS(ld) tKttlf.) issue,) 12-*>[ ll>i Table (ill. 1Itulft: incidence of fetal nmunulic`S. No VCM. no ethanol 'J fetuses g; litters) affected .Hat ppm VCM, no ethanol No VCM. no ethanol 2.HK) ppm VCM No ethanol l.V; etiumol Kxtermi) examination Omphalocele Soft tissue examination Microphthalmia Oilatetl ureter Small kitlnev Skeletal examination Vertebrae, lumhar spurs Vertebrae, delayed ossification 0 0 2(7) 0 !(!) (UU) ICO (1 2(d) (I PCiSI1' 2<ldl *Sitfnifk'antiy ilifferent from iiir-icxfiosed control, ft - IMJ.V ''Significantly different from VCMex|sised group, /i : <l.(ir>. October 1981 (l..|(.'il n OtlPl (i IldiM Ti.'fct) 0 n 2T(."iO)* (1 I2lli! lloP) .Ml!')1, 2(d) .tYldP)1, 21IS1)" 175 i5 I r. K?" iC:- I; t: i t* f * i r i t incidence of a single anomaly, dilated ureter was significantly higher than controls (Table <i). Kthanol did not further increase the incidence of this anoma ly. The incidence of dilated ureter was significantly lower in the ethanol group as compared to the VCM exposed group. Only minor skeletal variants were observed at an increased incidence among the ex posed rats. Lumbar spurs occurred more often than controls among litters at 500 ppm, but not among those exposed to 2500 ppm VCM alone. This vari ant was again observed at an increased incidence among the litters of rats treated with the combina tion. The incidence of delayed ossification of verte bral centra was also increased in this group and is indicative of a slight delay in skeletal development. As in mice, these skeletal changes occurred in those treatment groups where the combination of high exposure levels of VC.M and ethanol produced evi dence of maternal toxicity and decreased fetal body measurements. Among rabbits, external and soft tissue anoma lies were observed at a low incidence in those groups exposed to 2500 ppm of VCM alone or in combination with ethanol (Table 7). These included a single fetus with a dilated cerebral ventricle at 2500 ppm and a single fetus with cleft palate from the group exposed to 2500 ppm plus WA ethanol. A dilated renal pelvis was observed in two fetuses from a single litter in the latter group. Two addi tional fetuses from this group exhibited an enlarged atrium of the heart. (Jssilicalion of the fifth slernebra was delayed at the 50(1 ppm level, but not at the 2500 ppm level of exposure. Only four litters were available for examination at the 2500 ppm of VC.M exposure level. These data show that the combination of VC.M exposure with ethanol in the drinking water was more toxic to the developing f**lus, as it was in the maternal animal, than exposure to VCM alone. However, neither treatment regimen was teratogenic in the species tested. Fetal effects consisted of increased incidences of minor skeletal variants in dicative of a delay in development in mice and rats. Similar skeletal changes (delayed ossification of stonichruo or vertebral centra and unfused slcrnebrac or bones of the skull) were observed by Schweiz et al. (.V) in these two species given 15'<f ethanol in drinking water. Thus, the exposure to high concen trations of VCM in combination with ethanol in the drinking water produced toxic effects in the devel oping embryo or fetus which were similar to those produced by ethanol alone. A similar lack of teratogenicity of VCM in mice and of VCM alone or in combination with ethanol in rats was reported recently by Ungvary el al. (/'). Several experiments were conducted. Exposure to 1500 ppm for 2-1 hr/day during organogenesis was reported to have no teratogenic or fetal effects External examination Soft tissue examination Skeletal examination Table 7A. Rabbits: incidence nr Rial anomalies. No VC.M. no ethanol No. fclu>r* (no. litters) examine i .VKi ppm V<'.M. -- no ethanol no ethanol Z.'SKI |.|im VC.M X o ethanol I.V; ethanol 1.731S) ;<m im liaeiS) lXfill.M IT(iS) |:ii;i IS) lllil'.O JU'.n lilKIO XL'Ili 10111 aji-li Toilo jrn'.ii Toilo Table 7 It. Itahhils; ineidenee of fetal anomalies. No VC.M no ethanol ri felu^o litter*) affected oiMi ppm VCM. no e thanol No VCM. i,.i ethanol o.Mmi ppm VC.M No ethanol l.v; ethaiml External examination Cleft palate Soft tissue examination Dilateil renal pelvis Dilated cerebral ventricle Hnlarp'eil atrium, heart Skeletal examination Slernebrae. delated ossilieation I) (1 n it :N77i `Significantly different from air-eX|iosci! eontrul, /# * (i.ii.'i. 176 li it 0 n xse.ilr' II 1) 0 II 311 111 O II |MC!.'o II itk t:u mu St 11 1 n sill) J-IU17I Environment til Health Perspectives R&S 021462 ; l I Ii ;l t i! f ii >. li i l -4 i ? ]i4 ' \ apart I'mm an increase in let;d liver weight. Kxposurc during the third purl of pregmmey produced no deleterious effects. whereas expo.si.in> during the early days of geslnlion increased fetal morlalily and resulleil in decreased fetid body weights. Kxposure to vinyl chloride iind simultaneous mainte nance on it liquid alcoholic diet during the neunilalion period produced evidence of skeletal retardation, but no malformations in rats. Though the exact days of gestation during which the different treat ment retrimens were employed were not stated by the author, the reported results arc in apparent agreement with those from our laboratory. A report by Mirkovn et al. I Hi) summarized the fetal and postnatal effects following exposure of pregnant fills to li. 15 mg/nf1 of VC.M bv inhalation throiijrhout the entire gestation period. An increase in early emhryo (h>aths (immediately idler blasto cyst imphmtiilion) and a decrease in fetid body weight were reported by these authors. Observed anomalies in the offspring included generalized hcmitiomas. ts-lbld increiise over controls) internal hydroeephahis (51,50 of the fetuses), eiieephaloeele (2.5.T;), and v:iriiilions of slernebrid ossification (`J.S'r of the fetuses). Several postnatal effects in dicative of hepaloloxicity and disturbances in the hepatobiliary system in the progeny following ii> iilvm exposure were also reported. The ti. 15 mgnv' level of exposure is equal to only 2,5 ppm of VC.M. The exact length of exposure periods and details of the testing methods employed, especially as per tains to vapor generation and analyses, were not reported by Mirkovn et a!.: thus no explanation for the differences in observed effects of VC.M is ap parent. The reported results are markedly incon sistent with those from our laboratory where a thousandfold increase in exposure level 25WI ppm was not embryolcthal in rats, and similar fetal anomalies were not observed. In summary, exposure of pregnant mice, rats or rabbits to VCM by inhalation al concentrations sufiiciently high to cause maternal toxicity was not teratogenic in any of these species. Fetal effects consisted of delayed skeletal development in mice al 500 ppm, an exposure level which was mater nally toxic, and an increase in the incidence of dilated ureter in rats following maternal exposure to 2500 ppm. In mice exposed to 500 ppm of Vl'M. the incidence' of fetal resorptions was incre>ase>d over concurrent air controls. The incidence of re sorptions observed in this group was at the high end of the range for historical control groups in our laboratory. lnge>stiou of 1 Wi ethanol in the drinking water enhaiK'cd the toxicity of inhaled VCM. Fetal body measurements we*l`e decreased among mice and rats given the eombinalion and increases in the oe-curreuee of skeletal variants indicative of delayed development Were observed in both Species, The fetal effects observed were similar to those reported for these test species following administration u! ethanol without VCM exposure. The incidence of resorptions was increased in rabbits given ethanol in combination with VC.M. and maternal toxicity was enhanced by ingestion of ethanol in all three species. KKKKKK.VCK.- I. Viola. I>. I... HicoIIi, A.. arc) f'|>m>\ A, 1 'lit i'is-ii < rcs|HiiiM- of r.ii skin. Iiiiil's iit.il Inna- in vinyl rlili,n>l>- ( Vi/icrf Jit*,', -tl: opt'd!* 11!*71) J Maltnm, t`. *1 nc \ aim* of predictive i*\peritmnlal bioa^-av* in mrwpatiomd ;rd environmental carcmoi.rchr*i'. An -\ ample vinyl chloride. Anil*io 1: l> t 1P7*h :i. ri**erh.J. I... ;uif) Jnlm*oin M. N. Ah>:io*atv.ima ofln**r in the manufacture of pwlyv invl chloride, -f < *rcup, .Mill. 1C. loii-lo) il'Clt 1. Infante, I', Hnctiyt-nic anti mutagenic rmk* in emnmuiutie* with |io|v\invl chloride product mil laciluie* Ann NA Acad. ScL `li\- .Y Kdmonds, 1.. I>.. Kail;. II.. anil Nis'im, .1 I,. ( ntiL'emia! nmlformation- an.l vinyl cidoride. l.ancet it; 1 *1" tl. Kdmonds, |,, I).. Anderson, r. K... Klynt. J. W.,.Ir . ami .lame,". M (Nnjjehital <vwrul nervou.* system mallorma turns and vitivl chloride monomer expo-uiv. a community sillily. 'IVra'.oloiry 17: 1x7 IiJ i IU7'i. 7 Hefner. i; K., sir Wiitanahe, I*. <1.. and <iehrmc. 1`- -I Preliminary of tin* fate nf inhaled unyl chloride monomer in rat'. Ann. N.V. Acad Sci `Jpc H-Vl 1M l!*Trii. Schwou. .A.. Smith. K. A., and Stapler. U K Ti-ratoc-mc potential of ethanol in mice, rat.* and rabbit* Teratolo^v s.i ;t,s.V:r.rj H'.iTm, in Staphs. U. K. Uetection of visceral alteration,>->11 mamma lian fetuses, Teratology p. A--*" (ii'Tli, in. Wilson. !, H. MethiHl for admini'-iei'ini: atent* ami iletect mu malformations m evjierimentai animal*. In: Teratology: Principles ami Trchniipii**, J. ^*il>on and J. Warkati.v, Kd* . I'niveoity of Chicago Press. Htaamn I!1**-'*, pp. 77. II. Uuvvmhi. A. ii A mte on the Mainint! #*fe|ear**l .*fnrimeim with Alizarin Ked-S. Stain. Techm.l. I 1^U lirjio lit. Siejfel, S, Ntm-paranu trie StatmHc' for the ltt-ha\iorat Sciences. Metiraw-Hill. New York. liO;, pp. !'-Iti 1 i:|. Steel. K. (i. Ik. and Torne, H. II IVmciple* ami l'ntce- d*.ire> i>f Statistics, McCraw-Mill, New York. pp. liiHhA. MM12. 1-1. Haseman. .1. K.. ami Hoel, In tl. Table of tlehan * generalized Wilco\on test with lised point sen*ori:ij.r. I. Statisl. CompLit. Siimil. d; 117-i:C> t lpTli. la. Knjfvarv, (I. The teratogenic effect of vinyl chloride. &Munkav.-delem pi. Mirknva. Y.. Mikhaylova, A., and Nosko. M. I.mbrio- loksichno t lerattfeuno deystviye na vimlkhlornle <hm- hryopiMc and tetrato^enic effects of vinyl chloride), /tiraveopaz. iiik Mn. ppt U!i7M. 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