Environmental Health Perspectives Vol. 57, pp. 261-271, 1984



# Comparative In

# halation 

# Teratogenicity of 

# Four Glycol Ether 

# Solvents and
an 

# Amino 

# Derivative in 

# Rats*
by 

# B. K. 

# Nelson,t James V. 

# Setzer,t W. 

# Stephen 

# Brightwell,t Patricia 

# R. Mathinos,* Maureen 

# H. Kuczuk,* Timothy 

# E. Weavert and Phillip 

# T. Goad§

Previous researchdemonstrated the inhalationteratogenicity ofthe solvent 2-ethoxyethanol inrats and rabbits. Asthis isoneofaclassofwidelyusedindustrial solvents, we investigatedtheteratogenicity offive structurally related compounds. Each chemical was vaporized and administered to approximately 15 pregnant rats inonetothreeconcentrations for7hr/dayongestationdays 7to 15, anddamsweresacrificed

on day 20. Fetuses were individually weighed, and two-thirds of them were fixed in Bouin's solution and examined for soft-tissue anomalies. The other one-third were fixed in alcohol, stained withAlizarin Red andexaminedforskeletaldefects. Datawereanalyzedonalitterbasis; threesolventswerecomparedwitha pooledgroup (N = 34) ofsham-exposedcontrols, andtheremainingtwowere comparedwithagroupof 15 controls. At concentrations which were apparently not maternally toxic, 2-methoxyethanol was highly embryotoxic, producingcomplete resorptions at 200 ppm; increasedresorptions, reducedfetalweights and skeletal and cardiovascular defects occurred at both 100 and 50 ppm. 2-ethoxyethyl acetate at 600 ppm induced complete resorption of litters; 390 ppm reduced fetal weights and induced skeletal and cardiovasculardefects, but onlyasingledefect was observedat 130 ppm. 2-Butoxyethanol evidencedslight maternal toxicityat 200ppmbutproducedno increase incongenital defects at that concentration. Neither 2-(2-ethoxyethoxy)ethanol (100 ppm) nor 2-methylaminoethanol (150 ppm) was maternally toxic or embryotoxic. In summary, shorteralkyl chainedglycol ethersproducedgreaterembryotoxicitythan those having longerchains, andtheesterproducedeffects equivalent totheether, bothpatternspredictable from the biochemical literature.



### Of the thousands of 

### chemicals to 

### which workers are 

### exposed, only a 

### few have even 

### minimal 

### experimental animal data from which to 

### evaluate or 

### predict reproductive toxicity. 

### One class of 

### chemicals that has 

### demonstrated 

### reproductive toxicity is a 

### class ofmono

### and 

### dialkyl ethers of 

### ethylene 

### glycol and their 

### derivatives, 

### collectively referred to as 

### cellosolves or 

### glycol ethers. 

### Approximately 700 

### million 

### pounds (318 

### thousandmetric tons) 

### of

### glycol etherswere

### produced in 

### 1977, 

### withthe

### ethyleneglycolmonoethers

### representing about 

### 78% of the 

### total 

### production (1). 

### Ethoxyethanol, the 

### prototype of this 

### class, has the 

### largest 

### production volume, followedby

### butoxyethanol and

### methoxyethanol (1). 

### The 

### glycol ethers are 

### widely used in 

### industry as

*This manuscript was not presented as part of the conference proceedings. 'Division of Biomedical and Behavioral Science, NIOSH 4676 Columbia Parkway, Cincinnati, OH 45226. tDivision ofPathologic Embryology, Children's Hospital Research Foundation, Cincinnati, OH 45229. §Intox Laboratories, Inc., 914 Barber Street, Little Rock, AR 72202. 

### solventsfor

### nitrocellulose, lacquers, 

### inks, dyes, enamels, 

### varnishes, 

### varnish removers, 

### and 

### dry 

### cleaning com

### pounds. In

### addition, they are 

### used in some 

### commercial products 

### such as 

### cosmetics and 

### liquid household cleaners. 

### Producedand

### distributedbyat

### leastsix

### major American

### chemical companies, the 

### glycol ethers have a 

### combined 

### potential exposure 

### population of 

### around 1.5 

### million 

### workers in 

### the 

### United States. The earliest evidence of

### reproductive toxicity of

### this 

### chemical group was 

### observed when 

### skeletal defects

were 

### reported in 

### offspring of rats 

### following 100 

### ,ug/kg/day IP 

### injections of 

### ethoxyethanol throughout 

### gestation, although no 

### defects were 

### noted in mice or 

### rabbits (2). The same 

### investigators 

### administered 

### ethoxyethanol at 400 

### ,uL/kg/day for 4 

### weeks or 200 

### ,uL/kg/day for 13 

### weeks to 

### male rats 

### and 

### observed testicular 

### damage after both exposure 

### regimens. Re

### cently increased 

### skeletal variations were 

### observed fol

### lowing intubation of doses as 

### low as 

### 31.25 

### mg/kg/day methoxyethanol on 

### gestation days 7 to 14 

### in mice 

### (3). 

### Only recently, however, have there been reports of 

### teratogenic effects 

### produced by the 

### glycol ethers afterNELSON ETAL.



### administrationusing

### the commonroutes 

### ofoccupational

exposure, 

### inhalationandcutaneous 

### absorption. Skeletal 

### and cardiovascular defects were 

### observed in rats 

### after 

### dermal exposure to 

### 1.0 

### mL (0.25 

### mL, four times/day) 

### ethoxyethanol on 

### gestation 

### days 7 to 

### 16, 

### with nearly 

### halfofthe litters entirelyresorbed at 

### that level, and all 

### litters completely resorbed at 

### twice that level (4). 

### Gestational exposure 

### via inhalation to 

### 600 to 

### 750 ppm 

### ethoxyethanol produced complete 

### embryomortality in rats

### andrabbits, whereas 200 or 

### 160 ppm

### ethoxyethanol 

### induced 

### skeletal and cardiovascular 

### defects in rats 

### and 

### rabbits, respectively (5). 

### Increased neonatal mortality 

### following 

### inhalation exposure 

### of pregnant rats to 

### ethoxyethanol at

### the current 

### Federal occupational stan

### dard 

### (200 ppm) and 

### behavioral and 

### neurochemical alterations in

### the offspring ofpregnant rats 

### exposed to 

### one-half that 

### concentration (viz. 100 ppm) 

### have been 

### reported (6). 

### Dose-dependent increases in 

### testicular atrophy have 

### been 

### reported in 

### mice 

### following oral 

### administration 

### of various 

### glycol ethers at 

### 250 to 

### 4000 

### mg/kg/day, 5 

### days/week for 5 

### weeks (7). 

### The lowest levels causing 

### significant deviations from controls were as 

### follows: 

### methoxyethanol 250 

### mg/kg, 

### methoxyethyl acetate 

### 500 

### mg/kg; 

### ethoxyethanol 1000 

### mg/kg, ethoxyethyl acetate 

### 1000 

### mg/kg; butoxyethanol and phenoxyethanol pro

### duced 

### mortality in 

### all rats at 

### 2000 

### mg/kg but had no 

### effect on 

### testicular 

### weight at 

### 1000 

### mg/kg. The most 

### important 

### implication of these results is the indication that the 

### chemicals

### havingshorter

### attachedalkyl groups 

### producedthemost 

### damage andthatreproductive toxic

### itydecreaseswith

### increasingchainlength. Esterification 

### of the 

### compounds (i.e, 

### the acetate 

### forms) resulted in 

### less 

### testicularatrophywhen the dose was 

### calculated on

a 

### weight per 

### body weight 

### (mg/kg) basis (at 

### least with 

### methoxyethanol), but produced effects equivalent to 

### those 

### of the 

### alcohol form when calculated on a 

### molar basis 

### (thus implyingthat the acetate was 

### removed

### prior to 

### the 

### toxic 

### action). The present 

### research 

### evaluated the teratogenic 

### effects 

### ofstructurallyrelated glycol ethers in an attempt to 

### determine the structure 

### activity 

### relationships for 

### teratogenicity. Table 1 presents 

### the glycol ethers evalu

### ated for teratogenicity in 

### the present 

### research, 

### along 

### withthe same

### dataforethoxyethanol. As seen 

### fromthe 

### table, a 

### chemical having a 

### shorter alkyl chain was 

### selected 

### (methyl rather than ethyl), as was one 

### with a 

### longer chain (butyl), and were 

### the diethylene glycol 

### ethyl etherandtheethyl acetate. 

### The latter was 

### chosen 

### ratherthanthe etherin

### order to

### verifythat the acetate 

### wouldproduce effects equivalent to 

### the ether, as 

### would 

### be 

### predicted from 

### the ubiquitous nature 

### of esterases 

### withinthebodyand as 

### shownforthe

### male reproductive 

### effects 

### cited above. Finally, the amino 

### analog of 

### methoxyethanol was 

### tested to 

### determine the structural 

### specificity required to 

### produce teratogenic effects.


# Materials and Methods

Subjects Virginfemaleandmale

### Sprague-Dawleyrats

### specified to 

### be free 

### of 

### mycoplasma and 

### Sendai virus and of 

### internaland

### external

### parasites (Charles River

### Breeding Laboratories, Wilmington, 

### MA) were 

### acclimated to a 

### 12-hr 

### light-dark cycle (lights on at 

### 6 

### am) and to a 

### temperature of24 + 

### 2°C for 2 

### weeks. The

### humidity, not 

### controlled, typically was in 

### the range of 40 + 20%. 

### Purina Lab 

### Chow and tap water were 

### available ad 

### libitum except when 

### pregnant animals were in exposure 

### chambers. 

### Bedding consisted of 

### cleaned, heat

### treated sawdust from a 

### local 

### supplier 

### (Absorb-Dri, Tasty Foods, 

### Cincinnati, OH).



## Apparatus and Procedures

Males 

### weighing over 

### 300 g were 

### placed individually into a cage 

### with three females 

### weighing 200 to 

### 300 g.

Table 1. General information on the glycol ethers included in the present research.

Rat toxicity data

Common name Skeleton Oral, g/kg Inhalation, ppm/hr OSHA Standard NIOSH estimated and formula formula 

### LD50 LCL (TWA), ppm exposurepopulation 2-Methoxyethanol CH3OC2H4OH C-O-C-C-OH 2.46 2000/4H 25 97,285 2-Ethoxyethanola C-C-O-C-C-OH 3.0 4000/4H 200 359,790 C2H5OC2H4OH 2-Ethoxyethyl acetate 0
C2H5OC2H402C2H3 C-C-O-C-C-O-C-C 5.1 3000/4H 100 231,970 2-Butoxyethanol 

### C4HqOC2H4OH C-C-C-C-O-C-C-OH 1.48 500/4H 50 1,279,707 2-(2-Ethoxyethoxy)- ethanol (carbitol) C-C-O-C-C-O-C-C-OH 6.5 None None 20,000 

### C2H5OC2H4OC2H4OH 2-Methylaminoethanol 

### CH3NHC2H4OH C-N-C-C-OH 2.34 None None Unknown 

## aInvestigated inprevious research. 262GLYCOL ETHER TERATOGENICITY



### Vaginal smears were 

### taken each 

### morning, and the

presence 

### of sperm

### marked 

### day zero 

### ofgestation. These 

### females were

### placedalonein

### 38 x 

### 33 x 

### 17-cm

### polycarbonate cages 

### with 

### filter tops. 

### Feed and water 

### intake and 

### maternal 

### weight were 

### recorded weekly (i.e., on

### days 7, 

### 14, 

### and 21); any 

### other signs 

### ofmaternal toxicity were 

### noted 

### daily. The 

### glycol ethers (technical grade, 98 to 

### 99.5% pure; 

### Eastman 

### Kodak Co., Rochester, NY) were 

### heated in a 

### flask set 

### in 

### hemispherical mantles. 

### Vaporization was 

### achieved 

### by bubbling air 

### through each 

### solvent which

was 

### heated to 

### approximately 40°C (for the higher 

### concentrations). This vapor was

### thenmixedwithfiltered

room 

### air to 

### obtain the 

### desired concentration and introduced 

### into 0.5 m3 exposure 

### chambers (Charles Spengler and

### Associates, Cincinnati, OH). Theconcentration was 

### continuallymonitoredby a

### Miran I 

### infrared spectrophotometer 

### (Foxboro

### Analytical, SouthNorwalk, CT) with 

### the 

### concentration recorded 

### hourly. Typically, two or 

### three 

### charcoal tube 

### samples (silica gel 

### tubes for 2- 

### methylaminoethanol) were

### takenweeklyfrom

### thechamberair

### for

### independentverificationof

### the concentration 

### by gas 

### chromatograph. Two 

### exceptions are 

### notedbelow where more were 

### taken (9). 

### Throughout this paper 

### concentrations are 

### expressed in parts 

### of 

### solvent per 

### million parts 

### of 

### air; hence values 

### for the 

### different chemicals are 

### comparable on a

### molar equivalent basis. Air flow 

### through the 

### chambers provided approximately 

### four

### air

### changes per

### minute. 

### Exposures were 

### conducted 

### sequentially in one or two 

### chambers, with a 

### third chamber for sham exposure 

### of 

### control subjects. Pregnant females were 

### transported 

### from the animal quarters to

### the

### inhalation chambers in

### theirhome cages 

### with 

### filter tops 

### (Hazleton Systems, Aberdeen, MD). 

### They were 

### placed individually in 13 x 

### 25 x 189-cm 

### stainless 

### steel wire 

### mesh cages 

### within exposure 

### chambers. 

### Control animals were

### placedin

### similarchambers 

### for the same 

### hours as 

### the exposed animals; a 

### pooled group 

### of 

### controls (N

= 

### 34) 

### served as 

### the 

### comparison group 

### for 

### the first three chemicals 

### examined. 

### Another group 

### of 15 

### controls served as 

### the comparison group 

### for 

### the last two 

### chemicals 

### examined,

as 

### these groups were 

### exposed at a 

### later 

### time (approximately 6 

### months 

### later) than 

### the first 

### three. Exposures, as 

### outlined 

### above, were 

### conducted 7 

### hr/day, andthe

### animals were 

### left in

### the 

### chamberforat 

### least one 

### additional hour blow-off time after vapor 

### generation terminated. 

### They were 

### thenreturnedin

### theirindividual housing cages to 

### the 

### animal quarters, 

### where water 

### bottles were 

### replaced. 

### Exposures were 

### conducted on 

### gestation days 7-15. 

### On day 20, 

### the 

### females were 

### individually weighed and 

### euthanized by 

### chloroform asphyxiation. The entire uterus was 

### removed and num

### bers 

### of 

### resorption sites 

### (classified as 

### early, middle or 

### late) and live 

### fetuses wvere 

### determined. Fetuses were 

### serially removed, blotted of excess 

### fluids, weighed, examined 

### for external 

### malformations and external sex 

### determined. 

### One third of 

### the fetuses were 

### randomly selected and 

### placed in 95% 

### ethanol, and the 

### remaining fetuses were 

### placed in 

### Bouin's solution. After 

### being in the 

### Bouin's solution 

### for at 

### least 1 

### week, these 

### fetuses

were 

### examinedforvisceralabnormalitiesusingWilson's

razor

### blade sectioningtechnique (10). 

### The viscera were 

### examined with the 

### aid of a 

### dissecting microscope. A representative 

### sample of sections with 

### malformations

was 

### identified

### bydam

### numberand 

### savedin 70% 

### alcohol. Fetuses were 

### examined forskeletaldefects

### by

### using a 

### modified 

### Staples technique (11). 

### They were 

### fixed in 

### 95% 

### alcohol, eviscerated andmacerated in 2% 

### KOH/Alizarin 

### Red 

### S solution. The 

### fetuses were 

### furthermacerated and 

### clearedinthe 

### appropriate solutions of2% 

### KOH/glycerin (60:40, 

### 40:60, 

### 20:80) and stored in 

### 100% 

### glycerin. A 

### crystal of 

### thymol was 

### added to 

### each 

### storage vial 

### to 

### retard fungal growth. 

### Storage vials were 

### individuallv identified 

### by dam number.



## Statistical 

## Analysis
Numbers of 

### implants and 

### proportions of

### resorptions

were 

### independently analyzedbyusing a 

### Kruskal-Wallis

Table 2. Concentrations of vapors generated in inhalation study.
Vapors generated, ppm Days of 

### By infrared By gas chromatography exposure (X ± SD) (X ± SD) Methoxyethanol 11 199.2 ± 0.98 b 29 101.4 ± 2.2 99.3 ± 16.3 19 50.6 ± 1.0 47.4 ± 5.9 Butoxyethanol 11 194.4 ± 6.1 b 20 153.3 ± 6.8 176.8 ± 8.3c Ethoxyethyl acetate 12 601.0 ± 3.47 594.9 ± 109.9 21 a 387.2 ± 8.7 12 a 128.9 ± 1.a 2-(2-Ethoxyethoxy) ethanol 29 a 102.2 ± 15.6 2-Methylaminoethanol 28 a 150.0 ± 15.2 

### aDue to equipment problems, suitable data for concentrations from the infrared analyzer were not available for these chemicals. 

### bGas chromatograph samples were not taken in these exposures. 

### cThis charcoal tube result is approximately 15% higher than that from the infrared analyzer (IR); since the IRprovided anessentially continuous daily record of exposures, we have used the figures (usually rounded to the nearer 10 ppm) from the IR throughout the text for all chemicalswheresuitabledatafromthe IRwereavailable. Where IRdatawerenotavailable, thecharcoaltuberesultswereusedwithinthe text. 263NELSON ETAL.



### test 

### corrected for ties, 

### with subsequent multiple com

### parisons to 

### determine where 

### the differences 

### occurred (12). Analysis of pup 

### weights 

### involved a 

### mixed model 

### analysis of 

### covariance 

### (with the 

### number of live 

### pups in 

### the 

### litter as 

### the covariate) 

### using maximum likelihood 

### estimation (13,14). The 

### model was 

### mixed, since there
was 

### both 

### within-litter and 

### between-litter variation. 

### Subsequently, pairwisecomparisons between the

### pooled control group 

### and 

### each treatment group were 

### performed. Incidence of 

### total defects and of total 

### variants were 

### compared using a 

### Kruskal-Wallis test with 

### multiple 

### comparisons (12) 

### with the litter as 

### the 

### experimental unit 

### and the level of 

### significance at 

### p< 0.05. 

# Results
The 

### concentrations within 

### the 

### exposure 

### chambers as 

### measuredbythe 

### infraredanalyzerwere

### relativelyclose to 

### those 

### obtained from 

### gas 

### chromatography (Table 2).


## Control
No 

### visceral or 

### skeletal 

### malformations were 

### observed in 

### fetuses from

### control dams. The types of

### visceral and 

### skeletal variants 

### observed in 

### fetuses from the control 

### treateddamswere 

### similarto

### those

### variants 

### observedin 

### chemically 

### exposed groups. 

## Methoxyethanol (ME) ConcentrationsofME 

### (Table2) were

### easily

### generated andwere 

### rapidly cleared from the 

### exposure chambers. There were no 

### overt 

### signs of toxicity in 

### the 

### pregnant rats in 

### any of

### the 

### groups. The 

### onlyweight 

### decrements in the 

### maternal animals were likely due to 

### increased 

### resorptions. As 

### shown in 

### Table 3, all 

### litters at the 

### highest

### concentration (200ppm) were

### entirelyresorbed. At 100 

### ppm, 

### about half of the 

### litters (18 of 34) were 

### entirelyresorbed, and 

### all 

### litters had 

### some 

### resorptions; the mean 

### weight of the live 

### fetuses was 

### reduced by 

### approximately one-third from the 

### control value. At 50 

### ppm 

### there was 

### approximately a 

### 3-fold 

### increase in 

### resorptions and 

### fetal weights were 

### reduced by 

### 20% compared to 

### the control 

### values. 

### Visceral malformations 

### (Table 4) were 

### found in 

### fetuses 

### from both 

### the 50 ppm 

### and 100 

### ppm 

### ME-treated dams, 

### but 

### onlythe 

### incidence of

### those from

### the 100 ppm 

### groupwas 

### significantlydifferent from

### the 

### controls (p S 

### 0.025). 

### Heart 

### abnormalities were the

### predominantmal

### formations observed in both 

### the 100 

### ppm and 50 ppm ME 

### groups. 

### Malformations ofthe

### retina, eye, 

### umbilicus and lungs of 

### ME-exposed fetuses were 

### also 

### observed but at a 

### frequency lower 

### than the 

### aforementioned. Wavy, 

### fused, and absent 

### ribs, 

### plus extra 

### vertebrae


### were 

### observed in 

### the 100 

### and 50 ppm ME 

### treatment 

### groups 

### (Table 5). 

### Additionally, tail 

### malformations were 

### observed in 

### the 100 ppm 

### group. 

### Statistical analyses of 

### these 

### pooled data indicate 

### significant differences from 

### controls for both the 50 

### ppm (p < 

### 0.025) 

### and 100 

### ppm 

### (p < 

### 0.05) treatment groups. Fetuses in 

### the 50 

### ppm 

### group 

### demonstrated more rib 

### malformations than fetuses in

### the 100 

### ppmgroup. The 

### failure ofthe 

### incidence of 

### malformations to 

### increase 

### with dose may be the 

### result of 

### increased embryo lethality 

### observed in 

### the high dose group. These data 

### indicate 

### that inhalation of 50 

### or 100 

### ppm ME 

### is 

### teratogenic in 

### the rat.

Table 3. Effects ofmaternal exposure to glycol ethers on pregnancy outcome. 2-Methoxyethanol

Numberpregnant/number mated Implants/dam (X) Litters with resorptions, % Resorptions/litter (X) Controls 50 ppm 34/41 14/17 12.7 12.5 14 9 (42) (64) 0.64 1.6a 100

ppm 34/38 12.5 34 (100) 9.8a 200 ppm 8 /11 12.6 8 (100) 12.6a 2-Butoxyethanol 150 200 ppm ppm 16/19 15/18 12.9 15.1a 4 9 (25) (60) 0.23 1.2 2-Ethoxyethyl acetate

130 390 600 ppm ppm ppm 15/15 15/20 9/9 14.5a 12.9 14.7a 7 9 9 (47) (56) (100) 0.49 2.3a 14.7a
Resorptions Early Middle Late 

### Tbtal (% of implants)


### Tbtal live fetuses Live fetuses/litter (X) (% of implants)

Live fetal weights (X) Female Male Standard error ofmeanb 21 15 1 2 1 2 23 19 (5) (11) 192

77 61 330 (77)

407 156 96 12.2 11.1 2.8 (95) (89) (23)

3.46 2.84a 2.29a 3.64 2.91a 2.49a 0.07 0.07 0.28 101

(100) 4 16 8 20

0 1 0 7 0 1 0 8 4 18 8 35 (2) (8) (4) (17)

0 206 203 211 0 12.6 13.9 14.0 (98) (92) (96) 175 10.8 (83) 78 19 6 103 (100)

0 0

3.28a 3.49 3.31a 2.74a 3.55a 3.66 3.46a 2.85a 0.10 0.10 0.10 0.10 

### aSignificantly different from controls at p < 0.05 (only data on implants, X resorptions, and fetal weights were 

### analyzed). 

### bIn no case was there a significant difference between sexes on this variable; hence, only the larger is presented. 264GLYCOL ETHER TERATOGENICITY

Table 4. Visceral malformations.

ME BU EEAC 50 100 150 200 130 390 Controls ppm ppm ppm ppm ppm ppm Number of litters 34 14 11 16 15 15 15

Number of fetuses examined 270 103 65 135 135 142 116

Cardiac malformation, no. (%) IV septal defect 0 4(4) 13(20) 0 0 0 6(5) Ringed aortic arch 0 1(1) 4(6) 0 0 1(1) 2(2) Rt.-sided aortic arch 0 1(1) 1(2) 0 0 0 0 Rt.-sided ductus arteriosus 0 0 0 0 0 0 1(1) Pulmonary valve stenosis 0 0 1(2) 0 0 0 0 TImcus arteriosus communus 0 0 1(2) 0 0 0 0 Levocardia 0 0 1(2) 0 0 0 0
Pulmonarymalformations Hypoplastic lungs 0 0 2(3) 0 0 0 0
Optical malformation Deformed retina 0 1(1) 0 0 0 0 0 Reduced eye size 0 0 1(2) 0 0 0 0

Miscellaneous Umbilical hernia 0 1(1) 0 0 0 0 2(2)

Tbtal fetuses normala 191 55 27 104 99 95 55

Ibtal fetuses malformed 0 8 19 0 0 1 7

Tbtal litters affected 0 6 10 0 0 1 3

Statistical significance NSb p < 0.025 NS NS NS p < 0.01 

### aNormal defined as having no visceral variations or malformations. 

### bNS = not significant at p = 0.05.

Table 5. Skeletal malformations.

ME BU EEAC 50 100 150 200 130 390 Control ppm ppm ppm ppm ppm ppm Number of litters 34 14 9 16 15 15 15

Number of fetuses examined 137 53 31 68 71 69 59

Vertebra malformations, no. (%) Extra 0 0 2(6) 0 0 0 0

RibsRudimentary 13tha 0 0 0 1(1) 0 0 0 Wavy 0 15(28) 5(16) 0 0 0 2(4) Fused 0 2(4) 0 0 0 0 1(2) Absent 0 1(2) 0 0 0 0 0

Tail Shortened 0 0 4(6) 0 0 0 0 Absent 0 0 1(2) 0 0 0 0

Total fetuses normalb 137 2 1 37 52 30 2
Tbtal fetuses malformed 0 16 10 0 0 0 4

Total litters affected 0 8 4 0 0 0 3
Statistical significance p < 0.025 p < 0.05 NSC NS NS p < 0.01 

### aConsidered a minor malformation. 

### bNormal defined as having no skeletal

### malformations or deviations. 

### CNS = not significant at p = 0.05. 265NELSON ETAL.

Table 6. Visceral variations.

ME BU EEAC 50 100 150 200 130 390 Control ppm ppm ppm ppm ppm ppm Number of litters 34 14 11 16 15 15 15 Number of fetuses examined 270 103 65 135 135 142 116
Cranial variations, no. (%) 

### Enlarged lateral ventricles 5(2) 21(20) 24(37) 0 5(4) 7(5) 22(19)
Cardiac 

### Enlarged atria 0 0 1(2) 0 0 0 0 Urogenital Hydronephrosis 4(2) 1(1) 2(3) 2(1) 3(2) 6(4) 6(5) Bilateral 1 0 1 2 1 1 5 Unilateral 3 1 1 0 2 5 1 Dilated renal pelvis 39(14) 23(22) 2(3) 13(10) 19(14) 25(18) 14(12) Bilateral 13 16 2 7 9 13 7 Unilateral 26 7 0 6 10 12 7 Low set kidney 6(2) 0 0 0 1(1) 2(1) 8(7) Hypoplastic kidney 0 0 0 0 0 0 1(1) Hydroureter 52(19) 8(8) 3(5) 17(13) 12(9) 34(24) 19(16) Bilateral 21 5 1 9 3 25 11 Unilateral 31 3 2 8 2 9 8 Misplaced testes 20(7) 11(11) 5(8) 10(7) 12(9) 5(4) 10(9) Bilateral 5 1 1 0 1 1 2 Unilateral 15 10 4 10 11 4 8
Tbtal fetuses normal 191 55 27 104 99 95 55 Total fetuses with variations 79 44 31 31 36 47 58 TItal litters affected 26 13 10 12 13 14 15
Statistical significance p < 0.01 p < 0.01 NSa NS NS p < 0.01
aNS = not significant at p = 0.05.



### Visceral variants 

### observed in 

### fetuses 

### from both ME-treated groups were 

### similar to 

### those variants observed in 

### control fetuses 

### (Thble 6); 

### however, their 

### frequencyin

### exposedgroups was 

### significantlyincreased above that for 

### the control group 

### (p < 

### 0.01). Skeletal variants were 

### significantly more numerous 

### in 

### fetuses 

### from both the 50 

### (p < 

### 0.01) and 100 ppm 

### (p < 

### 0.025) ME-exposed dams than were 

### variants in 

### fetuses 

### from control dams 

### (Table 7). These 

### data 

### indicate that inhalation of ME 

### did cause 

### growth retardation in 

### the rat. 

## Butoxyethanol (BU) Concentrations ofBU were more

### difficult to

### generate in 

### that the solvent 

### required heat to 

### generate even 

### the low concentrations. 

### Clearance time from the 

### chambers

was 

### also 

### longer than for ME. 

### This was 

### the 

### only one 

### of the chemicals which

### produced apparent 

### maternal toxicity [ranging from 

### hematuria, as 

### has 

### been 

### reported in 

### the literature 

### (15), to 

### death at 

### concentrations from 250 to 

### 500 

### ppm. 

### Based on 

### the 

### maternal 

### toxicity,

In a dose finding study conducted at the outset of the project, nonpregnant rats (250-300 g) were exposed to 250, 350 or 450 to 500 ppmBU (no charcoal tubeverification). Three offour rats exposed to 450 to 500ppmofBU for 6.5hrdiedwithin 36 hrafterterminationof 

### exposure 

### levels of 150 

### and 200 

### ppm were 

### chosen for the 

### teratology study. Pregnant rats 

### exposed to 

### 200 ppm 

### BU showed some 

### hematuria, but 

### only on 

### the first 

### day of exposure. 

### With that 

### exception, the dams 

### showed no 

### adverse effects. There was a 

### significant increase in 

### the mean

### number 

### of 

### implants in 

### the 200 ppm 

### BU group, 

### but since no treatment 

### began until 

### day 7, this increase was not 

### treatment-related. There was 

### also no 

### apparent 

### adverse effectupon

### thepups, as

### thenumberof

### resorptions, fetal 

### weights, and 

### incidence ofmalformations did not 

### differ from controls 

### (Tables 3-7). 

### (There was a 

### statistically 

### significant decrease in 

### fetal

### weights in 

### the 150 ppm

### BU groups, 

### but since 

### the 

### differences were 

### slight and there

were no 

### effects at 

### the 

### higher level, these 

### differences

exposure, and two ofthree nonpregnant rats died within 18 hr after exposure to approximately 350 ppm BU for 7 hr. Of three nonpregnant rats exposed for 7 hr to 250ppmBU, onediedwithin 18 hrafter exposure, and a second died after day 2 of exposure. With each of these concentrations, the exposed rats began showing various (legrees of hematuria 4 to 6 hr after onset of exposure, as has been reported elsewhere (15). From each of these concentrations, one rat survived, and these three animals were 

### placed together in a 41 x 32 x 18-cm steel cage. Approximately 1 week after exposure, the distal portion of the tail (about one-half the tail 

### length) became necroticandfellofforwas chewedoff. Observationsofasmallnumber of singly housed rats exposed 

### cutaneously to butoxyethanol woul(d suggest that each rat chewed its own tail off. 266GLYCOL ETHER TERATOGENICITY

Thble 7. Skeletal variations.

ME BU EEAC 50 100 150 200 130 390 Control ppm ppm ppm ppm ppm ppm Number of litters

Number of fetuses examined

Skull variations, no. (%) Incomplete ossification Frontal Parietal Interparietal Supraoccipital Maxilla 34

137 14

53

1(1) 16(30) 3(2) 16(30) 3(2) 15(28) 2(2) 17(32) 0 0 9 16 15

31 68 71

4(13) 0 15(48) 0 12(39) 1(1) 18(58) 0 5(16) 0 1(1)

1(1) 0 0 0

Vertebra Absent Sacral/caudal Incomplete ossification Thoracic Lumbar Sacral/caudal

Centra Absent Thoracic Lumbar Sacral/caudal Incomplete ossification Thoracic Lumbar Sacral/caudal Abnormal Thoracic Lumbar Sacral/caudal 0

0 0 20(15)

0

0

0

0

0

0 6(4)

0

0 35(66)

0 1(2) 21(40)

14(26) 0 23(43)

0 0 1(2)
40(75) 16(30) 3(6) 3(10) 4(6)

0 0 0 0 12(39) 9(13)

16(52) 0 1(3) 0 5(16) 0

0 0 0 0 0 0
21(68) 15(22) 16(52) 0 3(10) 0

Sternebrae 4-incomplete ossification Abnormal 2(2) 1(1)

RibsRudimentary 14th
Pelvic girdle Pubis Absent (not ossified) Incomplete ossification Illium Absent (not ossified) Incomplete ossification Ischium Absent (not ossified) Incomplete ossification 5(4)

1(1)

0

0

0

0 2(2)

Other Metacarpals (3 ossified)

Total fetuses normal

Tbtal fetuses with variations

Total litters affected 0
100

37

19

Statistical significance "NS

= not significant at p = 0.05. b130 ppm vs. 390 ppm, p < 0.05. 17(32) 11(21)

4(8)

9(17) 3(6)

0

0 1(2) 11(21)

19(36)

2

50

13 23(74) 3(4)

5(16) 1(1)

14(45) 3(4)

6(19) 0 5(16) 0 12(39) 0 5(16) 0 9(29) 0 6(19) 0

12(39) 0

1 37

30 31

9 10

p < 0.01 p < 0.025 NSa 0 1(1) 12(21) 0 0 5(9)

9(13) 10(14) 36(63)

0 1(1) 2(4)

0 0 0

0 0 0 0 1(1) 7(12)

0 0 0 0 1(1) 3(5)

O 1(1) 11(19)

52 30 2

19 39 56

8 14 15

NS p < 005b p < 0.01

15

69 15

59

1(1) 1(1) 1(1) 1(1) 0 12(21)

12(21) 10(17) 11(19) 0

0

0 0 7(10)

0 0 0

0 0 0
7(10) 1(1) 0 0

0 0 22(32)

1(1) 0 0

0 0 5(7)
11(16) 0 0 2(4)

0 0 26(46)

17(30) 0 1(2)

0 0 8(14)
32(56) 17(30) 0 267NELSON ET AL.

Table 8. Effects ofmaternal exposure to 2-(2-ethoxyethoxy)ethanol (2-EEE) or 2-methylaminoethanol (2-MAE) onpregnancy outcome.

Controls 2-EEE 2-MAE Number pregnant/number mated 15/16 20/21 18/24 Implants/dam (X) 13.1 13.4 11.9 Litters with resorptions (%) 10(67) 12(60) 10(56) Resorptions/litter (X) 1.3 0.9 0.7 Tbtal live fetuses 174 250 212 Live fetuses/litter (X) 11.6 12.5 11.8 (% of implants) Live fetal weights (FX) Female 3.26 3.19 3.59 Male 3.33 3.25 3.69 Standard deviation 0.30 0.25 0.31 Number (%) of litters 5(33) 6(30) 7(39) with abnormal fetusesa 

### aLitter with at least one fetus having either skeletal or visceral anomalies; detailed in Tables 9 and 10.

Table 9. Summary ofvisceral observations after exposure to 2-(2-ethoxyethoxy)ethanol or 2-methylaminoethanol.

Number of litters (fetuses)/percenta Control 2-EEE 2-MAE Number of litters 15 19 18 Number of fetuses examined 116 166 143

Malformations Cardiovascular: Double aortic arch 0 1(1)/.53 0 Missing innominate 0 1(1)/.53 0 Brain: Hydrocephalus (mild) 3(6)/8 1(4)/4 3(5)/4

Variations Testicular: (number males examined) 62 76 74 Undescended testes 0 0 1(l)/i Position variation 10(22)/39 13(17)/22 9(13)/17 Urinary: Dilated renal pelvis 3(4)/3 7(13)/7 5(5)/3 Dilated ureter 3(6)/5 9(19)/11 6(18)/11 Hydronephrosis 2(2)/2 3(4)/3 0 Hydroureter 3(3)/2 4(7)/4 5(6)/4 Ectopic kidney 1(1)/i 2(2)/1 0 Other: Abdominal hemorrhage 1(l)/i 1(l)/i 0 Liver hemorrhage 0 1(1)/i 0

Number of fetuses with variations 30 43 27 Percent normalb,c 89 ± 26 91 ± 21 92 ± 15 Number of fetuses 107 153 131 Percent abnormalb 11 ± 26 9 ± 21 8 ± 15 Number of fetuses 9 13 12 

### aMean of litter mean percent. 

### bMean of litter mean percent ± SD. 

### cIncludes fetuses with variations.

were 

### likely not 

### of 

### biological 

### significance.) After exposure to 

### 150 ppm 

### BU, rats 

### occasionally showed 

### slight hematuria on 

### the first 

### day of exposure, 

### but no 

### other 

### adverse effects were 

### noted in 

### the dams or pups; one 

### fetus with 

### cephalothoracomphalopagus was 

### observed, but 

### this was 

### likely a 

### chance occurrence 

### and not 

### treatment-related.


## 2-Ethoxyethyl Acetate 

## (EEAC)
Concentrations of 

### EEAC were 

### relatively easy to 

### generate 

### and 

### cleared 

### rapidly from 

### the chamber. Mater

### nal

### animals showedno overt

### toxicity; a

### weightreduction

was 

### observed at 

### higher 

### concentrations, but 

### this was 

### likely due to 

### increased 

### resorptions. As 

### shown in 

### Table 3, all 

### offspring from dams 

## exposed to 

### 600 

### ppm 

### EEAC

were 

### resorbed. At 390 

### ppm 

### there was a 

### significant increase in 

### resorptions and fetal 

### weights were 

### reduced 

### by

## 21%, andat 

### 130

### ppm

### there were

## slightbut

## significant decreases in 

### fetal 

### weights. Visceral malformations of the 

### heart and 

### umbilicus

were 

### observed in fetuses from the 390 

### ppm 

### EEACtreateddams 

### (Table4). 

### Onlyone

### fetus from

### the 130

### ppm 

### group

### had a

### heart

### defect. 

### Statistical

### analysis ofthedata 268GLYCOL ETHER TERATOGENICITY

T!able 10. Summary of skeletal observations after exposure to 2-(2-ethoxyethoxy)ethanol or 2-methylaminoethanol.

Number of litters (fetuses)/percenta Control 2-EEE 2-MAE Number of litters 14 19 18 Number of fetuses examined 58 84 69 Malformations Missing ribs 0 1(1)/1 0 Decreased thoracic vertebrae 0 1(1)/1 0 Variations Ribs: Rudimentary 14th 1(1)/2 5(7)/8 1(2)/4 Rudimentary lumbar 0 0 1(1)/1 Skull: Incomplete ossification Supraoccipital 0 1(1)/1 1(1)/1 Interparietal 1(1)/2 2(2)/3 1(2)/2 Parietal 1(1)/2 3(3)/4 0 Frontal 0 2(2)/3 0 Sternebrae: Decreased number ( < 4) 1(1)/2 1(1)/1 0 Split 0 0 1(1)/1 Misaligned 1(1)/2 6(6)/7 5(5)/7 Centra Thoracic Missing, half-sized 0 4(4)/5 0 Misshapen 1(1)/2 3(3)/3 5(5)/8 Appendages Decreased metatarsals ( < 4) 0 3(3)/4 0 Decreased metacarpels ( < 3) 0 1(1)/1 0 Pelvic girdle Pubis, missing, pinpoint 0 1(1)/1 2(2)/3 Ischium, missing, reduced size 0 1(1)/1 1(1)/1 Number of fetuses with variations 4 23 16

Number of fetuses with no variations 14(54)/93 19(61)/73 18(53)/77
ormalformations Percent normalb,e 100 ±0 99 ± 6 100 ± 0 Number of fetuses 58 83 69 Percent abnormal 0 1(6) 0 Number of fetuses 0 1 0 'Mean of

### ltter mean percent. bMean of litter mean percent ± SD. 'Includes fetuses with variations.


### indicated significant

### differencesbetweenEEAC treated and control 

### groups 

### (p < 

### 0.01); 

### furthermore, since heart 

### defects 

### rarely occur 

### spontaneously, and none were 

### observed in control 

### fetuses, these data indicate that inhalation of 

### either 130 

### ppm 

### of 390 

### ppm 

### EEAC is 

### teratogenic in 

### the rat. 

### Malformations of the 

### ribs were 

### observed in 

### three fetuses from390

### ppm

### EEAC-exposeddams 

### (Table5); no 

### skeletal 

### malformations were 

### observed in 

### fetuses from the 130 

### ppm 

### EEAC group. 

### Statistical analysis ofthese data 

### indicated 

### significant differences from 

### the controls 

### (p < 

### 0.01); 

### however, due to 

### the low 

### frequency of
occurrence 

### of these 

### malformations, treatment-induced
cause 

### cannot 

### be 

### positively concluded. Visceral 

### variants observed in 

### fetuses from 

### EEACtreateddams were 

### similar to

### thosevariants observed in 

### control fetuses 

### (Table 6); 

### however, the 

### frequency of 

### variants in 

### the 

### exposed groups was 

### significantly different from the control-treated group 

### Significant statistical

### differences in

### skeleltalvariants 

### (Table7) were 

### observed between control and 130 

### ppm 

### (p < 

### 0.05) and 390 

### ppm 

### (p < 

### 0.01) and also between 130 ppm 

### and 390 ppm treatment 

### groups (p < 

### 0.01). (p < 

### 0.05). These data 

### indicate that inhalation of 

### EEAC at 

### either 

### dose level 

### during the period of organogenesis can cause 

### growth retardation in 

### the rat. 

## 2-(2-Ethoxyethoxy)ethanol (Carbitol, 2-EEE)
Due to 

### the low vapor pressure of 

### 2-EEE, 

### higher concentrations could not 

### be tested due to 

### probable formation of an 

### aerosol 

### (this was 

### observed 

### during chamber 

### calibration). No 

### toxicity was 

### observed in 

### maternal animals or

### in

### the

### offspring (Tables 8-10) after exposure to 

### 100 

### ppm 2-EEE 

### (mean concentration from 65 

### charcoal tubes or 

### 2 to 

### 3 

### per 

### day = 

### 102 

### ppm). 

### Consequently, 2-EEE is 

### likelynot 

### a

### teratogenic hazard 

### after 

### inhalation exposure. Nor is it 

### of 

### teratogenic risk 

### when 

### given in 

### comparable molar 

### equivalents to a 

### cutaneously teratogenic (4) level of 

### ethoxyethanol 

### (Nelson, unpublished 

### observations). 269NELSON ETAL.


## 2-Methylaminoethanol (2-MAE)

Low vapor pressure 

### also 

### prevented our 

### generating 

### high concentrations 

### of 2-MAE. At 150 ppm 

### 2-MAE (mean 

### concentration from 28 

### silica gel tubes, one per 

### day, 

### analyzedin

### duplicate = 

### 150.0ppm), no

### maternal or 

### fetal 

### toxicity was 

### observed (Tables 8-10). 

# Discussion

In 

### this study 

### of the inhalation 

### teratogenic effects of 

### four 

### glycol ethers 

### and an 

### amino 

### derivative, 

### methoxyethanol was 

### themost 

### embryotoxic; 

### ethoxyethyl acetate


### was 

### lesspotent; 

### but

### butoxyethanol, 

### 2-(2-ethoxyethoxy)- ethanol, and 

### 2-methylaminoethanol were not 

### embryotoxicat

### theconcentrationstested. 

### Congenitalmalformations in 

### mice 

### have been 

### reported after the mice were 

### intubated with various levels of ME on 

### gestation days 7-14 (3). 

### Comparing the frequency 

### of resorptions in 

### that 

### study with the 

### frequency of 

### resorptions we 

### observed, it appears 

### that our 

### level of 100 

### ppm 

### ME 

### would

### roughlycorrespondto

### theirdoseof250

### mg/kg. At
one 

### half that level (50 ppm 

### and 125 

### mg/kg) in 

### both 

### studies, there was 

### little increase in 

### resorptions, but 

### malformations were 

### observed. 

### Since the 

### study in 

### mice 

### (3) 

### found malformations at 

### levels lower than this 

### (even at 

### their lowest dose of 31.25 

### mg/kg), it is 

### possible that malformations 

### couldbe induced

### byconcentrations 

### lower than our 

### low level 

### of 50 ppm. 

### The results from 

### ethoxyethyl acetate were as 

### expected. Based upon 

### the 

### ubiquitous nature 

### of the esterases 

### within the 

### body, and upon

### work

### with testicu

### lar atrophy (7), we 

### had 

### predicted at 

### the outset 

### of 

### the 

### study that, calculated on a 

### molar 

### basis, EEAC would 

### have precisely

### the same 

### effects as 

### ethoxyethanol (EE). 

### Consequently, 600 ppm 

### EEAC was 

### expected to, 

### and 

### did, induce 

### complete 

### embryomortality as 

### 600 ppm 

### EE 

### had done (5,16). At 390 ppm 

### EEAC, resorptions were 

### only slightly 

### increased, 

### though fetal 

### weights were 

### depressed and 

### malformations were 

### observed. At 130 ppm 

### EEAC, fetal 

### weights were 

### still 

### depressed and there was 

### one 

### defective 

### fetus, 

### indicating that this level is near 

### the 

### teratogenic threshold but 

### should still 

### be considered 

### teratogenic in 

### the rat. 

### Thus, there is a 

### relatively steep 

### dose-effect curve 

### with 

### EEAC, and the

same can 

### be 

### said of 

### 2-ethoxyethanol and ME. 

### Butoxyethanol appears to 

### be rather 

### unique in 

### this 

### series, in 

### that it 

### produces maternal 

### toxicity at 

### levels below 

### those which

### produce 

### embryotoxicity. Its 

### toxicity and hemolytic effects have been 

### described (15), with a 

### recent 

### study verifying and 

### extending the 

### previous report 

### (17). The same 

### investigators also indicated (15) 

### that the 

### likely metabolic 

### product is 

### butoxyacetic acid, 

### and that the 

### majority of the 

### metabolite is 

### excreted within 24 

### hr. 

### That the 

### excretion is 

### fairly rapid is also 

### suggested from our 

### results in 

### that the hematuria was 

### observed only on 

### the first 

### day of exposure. 

### As is 

### apparently true 

### with most 

### of the 

### glycol ethers, BU is 

### readily absorbed 

### through the 

### skin (18). 

### Our incidental observation 

### of necrosis in the 

### tails of rats 

### exposed to BU was not 

### noted in the 

### literature. 

### Whether the 

### necrosis was 

### due to 

### damage in 

### the 

### extremity of the 

### peripheral nervous 

### system (in 

### the 

### tail) or to 

### the lack of oxygen 

### and 

### nutrients provided by the 

### blood of the region is unknown, though the known 

### effects of BU on 

### the 

### blood suggest 

### the latter as a 

### strong 

### possibility. Theoretically, one 

### of the 

### biotransformation 

### products 

### of 2-EEE 

### wouldbe 

### 2-ethoxyethanol (or 

### its 

### biotransformation products). Thus it may 

### be that high 

### levels of 

### 2-EEE would be teratogenic, 

### though this remains as 

### only speculation since we 

### could not generate 

### higher 

### levels of 2-EEE as a vapor. 

### Considering all 

### of these results in 

### conjunction with 

### the 

### previously 

### reported teratogenic 

### effects of 2-ethoxyethanol, it appears 

### that longerchain

### glycol ethers are 

### less embryotoxic than

### the 

### short-chain glycol ethers; thiswouldbe expected

### due to 

### the 

### relatively lower 

### lipid solubilities 

### ofthe longer 

### chain 

### compounds (19). 

### Further, based on our 

### results with 2-ethoxyethyl acetate, it is 

### likely that the acetates 

### of 

### other 

### glycol ethers would have similar 

### reproductive toxicity to 

### their corresponding 

### ethers. Finally, the 

### lack ofteratogenic response 

### of2-methylaminoethanol was 

### interesting

### andfroma

### mechanistic or 

### theoretical point 

### ofview, 

### wouldmerit followup 

### using a 

### different route 

### of exposure. 

### At 

### first glance, one 

### might expect 

### that its biotransformation 

### would be similar to 

### that of 2-ME. However, our 

### results 

### of no 

### maternal or 

### fetal 

### toxicity at 

### 150 

### ppm 

### 2-MAE suggest 

### that this may not 

### be the case; 

### since the amine 

### is 

### likely more 

### lipid

### solubleandless

### water-solublethanthe

### methoxyportion, the 

### absorption and excretion 

### of the 2-MAE is 

### likely 

### quite different from that of 2-ME. Thus it 

### would be 

### of interest to see 

### if a 

### higher dose of 2-MAE 

### would be teratogenic, thougha

### route 

### otherthaninhalation

### would be

### required, since the vapor

### concentrationwe

### usedwas near 

### the saturation point.' This 

### lack of teratogenicity at 

### three times 

### the concentration of a 

### teratogenic 

### level of its 

### structurally similar 

### glycol ether, points to a 

### relatively strict structural requirement to 

### produce 

### teratogenic effects. The present 

### studydoes not 

### elucidate 

### the mechanism of action 

### by which the solvents 

### induce 

### embryotoxicity. Nor 

### did we 

### determine 

### biotransformation 

### pathways, though it is 

### likely that each 

### glycol ether 

### undergoes

* One purpose of this studywas to select another glycol ether for inclusion in a behavioral teratology study. As exposure to 200 ppm 2-ethoxyethanol on gestation days 14-20 was previously reported to
cause neonatal deaths (6), small groups ofanimals were alsoexposed to the chemicals in the present study on gestation days 14-20. Maternal animals rearedtheiryoung (litters culled to fourfemale and fourmalepups onthedayofbirth) toweaning, andtheoffspringwere weighedweeklyfor5weeks. Theresultsindicatedthat 100ppm2-ME (N = 6) delayed parturition by approximately 36 hr and no pups survivedfor1week; 50ppm2-HE (N = 5)producedlittle, ifany, delay inparturition, andallpups survived. Exposure to 600ppmEEAC (N

= 3) delavedparturitionbyaround 24hrandproduced 75% mortality inthe offspring; 390 ppm (N = 3) delayedparturitionbyabout 12hr, but all offspring survived; neither 130 ppm EEAC (N = 4) nor 150 ppm BU (N = 4) produced any adverse effects in the offspring. 270GLYCOL ETHER TERATOGENICITY 271



### biotransformation via 

### alcohol and aldehyde dehydrogenase, yielding its corresponding 

### acetaldehyde and subsequently excreted 

### primarily as 

### the acetic acid derivative. We observed 

### that embryotoxicitydecreases
as alkyl chain 

### length increases, 

### similar to 

### observations with testicular atrophy (7). We 

### found that short-chain glycol ethers and their corresponding esters are 

### embryotoxic and 

### teratogenic in 

### rats. 

### Since previous research found similar effects induced by methoxy

### ethanol in

### mice via 

### intubation 

### (3) and 

### ethoxyethanol in 

### rabbits (5) via inhalation, and in rats via cutaneous exposure (4), 

### teratogenic effects have been induced in 

### three lower species of 

### animals by common routes 

### of human exposure. Such effects call for careful examination of 

### human 

### populations exposed to 

### this class of solvents, 

### particularly since these effects in 

### animals
were 

### observed at 

### concentrations which are at or

### below current 

### permissible exposure limits. NOTE: Since the time 

### this paper was 

### prepared, there has been a

### proliferation of

### research on 

### the 

### glycol ethers; we 

### referreaders to 

### the 

### otherpaperin

### this issue for more recent 

### research.

We thank Dr. Bill Scott and the staff at Children's Hospital Research Foundation for their assistance, Dr. Kent Anger for his support and review ofthe manuscript, Mr. Randy Smith forhis help with the statistical analyses, and Mrs. Nadine Dickerson for her uncomplaining typing and correcting of the manuscript. Mentionofcompanynamesorproductsdoesnotconstituteendorsement by the National Institute for Occupational Safety and Health.

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