Reaction mass of 2,2'-(ethylenedioxy)diethanol and 3,6,9,12,15-pentaoxaheptadecane-1,17-diol and 3,6,9,12-tetraoxatetradecane-1,14-d

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

No data.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was not conducted according to guideline/s and GLP but the report contains sufficient data for interpretation of study results.

Justification for type of information:

Read across based on category approach. Please see category document for further information.

Objective of study:

other: excretion and metabolism

Qualifier:

no guideline available

Principles of method if other than guideline:

Triethylene glycol was administered by oral gavage to rats and rabbits. Urine, feces and carbon dioxide were collected and analyzed for potential metabolites.

GLP compliance:

not specified

Radiolabelling:

yes

Remarks:

Randomly labeled triethylene glycol was synthesized by reaction of 14C ethylene glycol with ethylene oxide.

Species:

rat

Strain:

other: albino

Sex:

male

Details on test animals or test system and environmental conditions:

Male rats were obtained from Albino Farms, Red Bank, New Jersey.

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Nonisotopic triethylene glycol was given by stomach tube to maIe albino rats in 25% W/V aqueous solution.

After receiving triethylene glycol-C14 (22.5 mg, 5.13 uc/mg, in 1 mI of water) by stomach tube, rats, varying in weight from 118 to 145 g, were housed in glass metabolism cages.

Remarks:

Doses / Concentrations:
Rats received triethylene glycol-C14 22.5 mg, 5.13 uc/mg, in 1 mI of water)

Non labeled triethylene glycol - 125, 140, 550, 600 and 790 mg/kg

No. of animals per sex per dose / concentration:

Two per dose level.

Control animals:

yes, concurrent no treatment

Positive control reference chemical:

No data.

Details on study design:

Administration of Triethylene Glycol and Excretion by Animals
Nonisotopic triethylene glycol was given by stomach tube to maIe albino rats in 25% W/V aqueous solution. Urine was collected over sodium fluoride as runoff from metabolism cages, and all animals were allowed food and water ad libitum during the course of the experiment. Urine samples were used directly or stored frozen.

Excretion of Radioactivity by Rats
After receiving triethylene glycol-C14 (22.5 mg, 5.13 uc/mg, in 1 mI of water) by stomach tube, rats, varying in weight from 118 to 145 g, were housed in glass metabolism cages. The animals were allowed water but no food. Urine and feces were separated by a screen. Expired CO2 was collected in sodium hydroxide solution and counted at infinite thickness as barium carbonate in comparison with triethylene glycol standards at infinite thickness on talc. Dried samples of urine were counted at infinite thickness on talc. Fecal samples were oven dried at 100C and then counted at infinite thickness.

In control experiments, a 48-hour collection of urine from an untreated rat was collected in a glass metabolism cage; 0.5 ml of aqueous solution containing 11.3 mg of triethylene glycol-Cl4 was added to the urine. Air was passed through the cages for 2 days as in the metabolic experiments. Aliquots of the urine recovered from the cage by rinsing with water were dried on talc and then counted. The radioactive experiment showed the presence of 95.0%,, 99.0%, and 99.870 of the added glycol.

Fractionation of Urine after Administration of Nonisotopic Triethylene Glycol
Following administration of triethylene glycol, urine from rats was made alkaline to pH 12-13 by addition of sodium hydroxide. The urine was then exhaustively extracted with chloroform as described in the section on control studies. The chloroform extract contained triethylene glycol which was determined calorimetrically. An additional sample was then subjected to acidic hydrolysis as described in the section on control studies. The urine was then made alkaline as above for extraction of total triethylene glycol (free plus that from hydrolysis of any glucuronide ester) by chloroform. Some urine samples were acidified to pH 2-3 and then extracted with chloroform to obtain material, not extractable from alkaline solution, putative 0- (P-hydroxyethyl)oxyethoxyacetic acid, which was converted into a chromatogen by reaction with 3,.5-dinitrobenzoyl chloride for the calorimetric determination.

Vapor Phase Chromatographic Determination of an Acid Derived from the Metabolism of Triethylene Glycol
The chloroform solution obtained by a continuous exhaustive extraction (72 hours) of acidified rabbit urine obtained after administration of triethylene glycol was evaporated to dryness. The residue was transferred to a 50-ml glass-stoppered bottle with the aid of 2 ml of absolute methanol. After addition of 0.2 ml of concentrated hydrochloric acid and 2,2-dimethoxypropane (cf. Lorette and Brown, 1959), the mixture was shaken and allowed to stand at room temperature for 1 hour. An aliquot (0.2 ml) was chromatographed by the preceding procedure for vapor phase chromatographic determination of triethylene glycol in urine. The recorder response was equivalent to 1% by weight of triethylene glycol in the urine (approximately 3 times that obtained from a similar extraction of alkalinized urine). The aqueous residue from extracted alkalinized sample was then acidified to pH l-2 by addition of hydrochloric acid, The acidic solution was then exhaustively extracted with chloroform. The chloroform solution which contained no triethylene glycol was then evaporated and subjected to the esterification procedure (above). The esterified product had a retention time (8.5 minutes) on the Carbowax column which was identical to that of triethylene glycol. In comparison the dimethyl ester of ethylenedioxydiacetic acid had a retention time of 7.5 minutes. The esterified metabolite, collected from the column, and the dimethyl ester showed a similar infrared absorption spectrum. The former, however, showed a strong OH absorption at 2.9 u.

Another chloroform solution from the exhaustive extraction of the acidified urine (5 ml) was evaporated and then subjected to esterification with methanol (see above). To the residue obtained by evaporation of the esterification mixture was added 2 ml of acetic anhydride. The mixture was heated to 90” C for one-half hour. An aliquot (0.1 ml) was subjected to chromatography in the Perkin-Elmer Vapor Fractometer equipped with a column Q17 (2 meters packed with Apiezon L on Chromosorb Red). The column was adjusted to 200” C at a helium flow rate of approximately 150 ml/min. The peak at a retention time of 16 minutes, corresponding to acetylated triethylene glycol, indicated a triethylene glycol content corresponding to that obtained by chromatography of the chloroform extract of alkalinized urine. An earlier peak at 10.5 minutes differed from that obtained of an authentic sample of the dimethylester of ethylenedioxydiacetic acid (13 minutes). The peak responses of the acetylated and esterified metabolic triethylene glycol (0.6870 by weight in the urine) and that of the acetylated unmetabolized triethylene glycol of the sample (0.31% by weight in the urine) were in good agreement with the results obtained above on the Carbowax column. Evidence that triethylene glycol was determined as an acetyl derivative and that the metabolite was determined as an acetyl methyl ester was confirmed in experiments in which it was shown that neither triethylene glycol, ethylenedioxydiacetic acid, nor the methyl ester of the metabolite would pass through column Q, even when the temperature was raised to 220 C.

Fractionation of Radioactivity in Rat Urine after Oral Administration of Triethylene Glycol-Cl4
The urine plus water washings from the cage of rat no. 4 were filtered through Celite and concentrated at 37” C to a volume of 51 ml. An aliquot was made strongly alkaline by addition of ammonia water and was extracted continuously with chloroform for 3 days to obtain 59.5% of the administered radioactivity. After an additional 24-hour extraction, 0.4% additional of the administered activity was recovered. The chloroform extract was then subjected to paper chromatography on Whatman no. 1 paper with the chloroform-n-propanol ammonia system. A single radioactive zone was located on X-ray film (Rf 0.62). This substance cochromatographed with an authentic sample of triethylene glycol. The ammoniacal solution remaining from the preceding extraction was made strongly acidic by addition of concentrated hydrochloric acid and then was extracted exhaustively with chloroform to obtain 44.2% of the administered radioactivity. The chloroform solution was subjected to paper chromatography using a solvent system: 7.5 ml see-butyl alcohol, 14 ml 90% formic acid, 11 ml water (Hausman, 1952).

Investigation of Cl4 Activity in Urinary Oxalate Fraction
The urine and water washings from the cage of rat no. 5 were concentrated to a volume of 50 ml. The sample was heated at 100” C for onehalf hour after addition of 4 ml of concentrated hydrochloric acid. The sample was made alkaline with ammonia water and 1 ml of 5% aqueous calcium chloride was then added (Dakin, 1907). The resulting precipitate was washed 3 times with water and then dissolved in dilute hydrochloric acid. A precipitate was formed again by addition of ammonia water. The precipitate was again washed with water and redissolved in dilute hydrochloric acid. The solution was extracted with ether. The ethereal solution was dried over anhydrous sodium sulfate and concentrated to dryness. The residue was dissolved in 5 ml of water and treated with ammonia water until slightly alkaline; 0.25 ml of 5%. aqueous calcium chloride was then added. The resulting fine suspension was allowed to stand for several days and then collected by centrifugation. The supernatant liquid was assayed for radioactivity in the scintillation counter. The precipitate was dissolved in 2 ml of 1 N hydrochloric acid. After radioactivity was determined, the solution was treated with 100 mg of oxalic acid dihydrate and 2 ml of concentrated hydrochloric acid at 100” C for one-half hour. A sample of the solution (0.1 ml) was removed for radioactivity determinations. The remaining solution was extracted continuously with ether for 14 hours. The ethereal solution was evaporated to dryness. The residue was dissolved in hot water. Upon cooling, two fractions of oxalic acid, m.p. 99-101” C, were obtained. These were put into solution for scintillation counting.

The supernatant liquid from the oxalate fraction was examined by descending chromatography on Whatman no. 41 filter paper in comparison with authentic samples of oxalic acid and ethylenedioxydiacetic acid with a solvent system of ethanol (4 vol) and 16% aqueous ethylamine ( 1 vol) (Long et al., 1951). The radioactive unknowns were scanned with the Actigraph II system and the reference strips were sprayed with universal pH indicator solution.

References:
HAUSMAN, W. (1952). Amino acid composition of crystalline inorganic pyrophosphatase isolated from bakers’ yeast. J. Am. Ckem. Sot. 74, 3181-3182.

LONG, A. G., QUAYLE, J. R., and STEDMAN, R. J. (1951). The separation of acids by paper partition chromatography. J. Chem. Sot., 2197-2201.

LORETTE, N. B., and BROWN, J. H., JR. (1959). Use of acetone dimethyl acetal in preparation of methyl esters. J. Org. Ckem. 24, 261.262.

Details on dosing and sampling:

After receiving triethylene glycol-C14 (22.5 mg, 5.13 uc/mg, in 1 mI of water) by stomach tube, rats, varying in weight from 118 to 145 g,

Statistics:

No data.

Type:

excretion

Results:

86.1 - 94.0% of the administered dose was recovered within 5 days in the urine. In two of four rats examined, >85% of the administered dose was recovered within one day.

Details on absorption:

No data.

Details on distribution in tissues:

No data.

Metabolites identified:

yes

Details on metabolites:

After oral doses of triethylene glycol the rat and the rabbit excrete triethylene glycol in both unchanged and oxidized form. The data suggest that one of the oxidation products is a monocarboxylic acid which arises by metabolic oxidation of a single terminal hydroxyl group of the parent glycol.

Bioaccessibility (or Bioavailability) testing results:

No data.

A series of paired rats were given triethylene glycol orally in doses ranging from 125 to 600 mg/kg (Table 1). The values for triethylene glycol recovered in the 24-hour urine samples were 27.4 to 66%. The calorimetric data on extracts of acidified urine again showed enhanced values consistent with the possible presence of a hydroxy acid from the metabolism of triethylene glycol.

Following oral administration of triethylene glycol-C14, the rat (Table 2) showed a consistently high elimination of C14 activity, the urine serving as the major excretory route in all cases. At the end of a S-day period, the total recovery of C14 was 91-98s of the administered dose. Approximately 95% of the recovered activity, or 90% of the C14 dose, appeared in the urine. A lesser amount appeared in the feces and an indeterminate amount of fecal radioactivity arose through contamination by urine.  Respiratory carbon dioxide afforded, in the 4 rats studied, elimination of only 1% of the activity in the dose of glycol, and most of this activity appeared during the first 12-hour period after administration (Table 3).

Similarly, the major urinary excretion of radioactivity appeared during the period of the first day following administration. The nature of the urinary radioactivity was approached by a variety of chemical and physical techniques.

The chromatographic examination of products coprecipitated with calcium oxalate from the urine of rat no. 5 yielded in addition to material with Rf corresponding to oxalic acid (origin to Rf 0.35) two other acidic components, Rf 0.37 and Rf 0.48-0.57. The major component at Rf 0.37 was not identified. The Rf value of authentic ethylenedioxydiacetic acid (“ethylene bis(glycolic)” acid) was Rf 0.50. The combined radioactivity of all the components including oxalate was 0.0046% of the administered radioactivity. Following addition of carrier oxalic acid and several recrystallizations, the radioactive values indicated that at most only 3% of the above (0.00017, of administered radioactivity) was present as oxalic acid.

Fractions from the urine of rat no. 4 were subjected to chromatographic study by a different procedure, which served again to indicate the acidic nature of some of the metabolites arising from the metabolism of triethylene glycol and the absence of appreciable quantities of the lower glycols, diethylene glycol and ethylene glycol, which are considered to be physiologically undesirable. Chromatography and autoradiography of the chloroform solution obtained by continuously extracting the alkalinized urine revealed the presence of one radioactive zone, corresponding in Rf value and cochromatography to authentic triethylene glycol. A chloroform solution, obtained subsequently by continuously extracting aqueous residue of acidic pH, contained two radioactive zones, Rf 0.64 and Rf 0.84, upon paper chromatography in the set-butyl alcohol-formic acid-water system. The zone at Rf 0.84 was not identified. Authentic ethylenedioxydiacetic acid chromatographed at Rf 0.64 under similar conditions.

Table 1 EXCRETION OF NONISOTOPIC TRIETHYLENE GLYCOL BY MALE ALBINO RATS

FOLLOWING ORAL ADMINISTRATION

			Colorimetric values for % of dose recovered in chloroform extracts.
Pair No.^a	Weight of pair (g)	Total dose (mg/kg)	Alkaline urine	Alkaline urine after acidic hydrolysis	Acidic urine after acidic hydrolysis
1	360	125	66.0	67.2	---
2	320	140	65.0	70.8	---
3	450	550	37.8	44.6	56.7^c
4	590	600	27.4^b	---	40.3
5	320	790	---	---	60.0 51.7

^a Two rats of approximately equal weight were used for each pair.

^b The value obtained by vapor phase chromatography was 30.8%.

^c Value for “hydroxyacid” = (56.7-44.6) X 2 = 24.2% of dose.

TABLE 2 EXCRETION OF TRIETHYLENE GLYCOL AND METABOLITES BY MALE ALBINO RATS FOLLOWING A SINGLE ORAL DOSE (22.5 MG) OF RANDOMLY LABELED TRIETHYLENE GLYCOL-C¹⁴

		Radioactivity recovered in 5 days as % of administered dose
Rat No.	Weight (g)	Expired air	Urine	Feces	Total
2	118	1.2	89.0	5.3	95.5
3	120	0.9	94.0	3.4	98.3
4	112	0.8	93.5^a	2.0	96.3
5	145	0.9	86.1^b	3.6	90.6

^a Daily urine values: Day 1 = 92.7; 2 = 0.53; 3 = 0.21; 4 plus 5 = 0.09.

^b Daily urine values: Day 1 = 85.2 ; 2 = 0.47 ; 3 = 0.29; 4 plus 5 = 0.15.

TABLE 3 ELIMINATION OF TRIETRYLENE GLYCOL AS RESPIRATORY CARBON DIOXIDE

	% of Dose as C^14O2
Rat No.	0 -12 Hr	12 -24 Hr	24 -36 Hr	36 -48 Hr	48 -60 Hr	Total
2	0.81	0.10	0.06	0.04	0.17	1.18
3	0.52	0.09			0.31 (24 - 60 hours)	0.91

Conclusions:

Interpretation of results (migrated information): low bioaccumulation potential based on study results
The major part of the radioactivity appeared in the urine. The data from fractionation of the urine indicated that only negligible quantities (if any) of Cl4 were present as oxalic acid.

Executive summary:

After oral doses of triethylene glycol the rat and the rabbit excrete triethylene glycol in both unchanged and oxidized form. The data suggest that one of the oxidation products is a monocarboxylic acid which arises by metabolic oxidation of a single terminal hydroxyl group of the parent glycol. After oral administration of triethylene glycol-C¹⁴ the rat eliminated only trace quantities of C^l4 activity as respiratory carbon dioxide. A small but measurable amount of radioactivity was found in the feces. The total elimination of radioactivity (in urine, feces, and expired air) during the 5-day period following a single oral dose (22.5 mg) was 91-98%. The major part of the radioactivity appeared in the urine. The data from fractionation of the urine indicated that only negligible quantities (if any) of C^l4 were present as oxalic acid. The major metabolic products had properties which suggested that triethylene glycol is degraded by the route: HOCH₂CH₂OCH₂CH₂OCH₂CH₂OH ---> HOCH₂CH₂OCH₂CH₂OCH₂COOH ---> HOOCCH₂OCH₂CH₂OCH₂COOH The foregoing data, showing a high degree of elimination of triethylene glyco] and its metabolites by way of the urine, is consistent with many findings pointing to the low or limited toxicity of triethylene glycol.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

No data.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was not conducted according to guideline/s and GLP but the report contains sufficient data for interpretation of study results.

Justification for type of information:

Read across based on category approach. Please see category document for further information.

Objective of study:

other: excretion and metabolism

Qualifier:

no guideline available

Principles of method if other than guideline:

Triethylene glycol was administered by oral gavage to rats and rabbits. Urine, feces and carbon dioxide were collected and analyzed for potential metabolites.

GLP compliance:

not specified

Radiolabelling:

yes

Remarks:

Randomly labeled triethylene glycol was synthesized by reaction of 14C ethylene glycol with ethylene oxide.

Species:

rabbit

Strain:

New Zealand White

Sex:

female

Details on test animals or test system and environmental conditions:

New Zealand White female rabbits were obtained from J. C. Heath, Ashland, Virginia.

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Nonisotopic triethylene glycol was given by stomach tube to New Zealand White female rabbits in 25% W/V aqueous solution.

Duration and frequency of treatment / exposure:

One rabbit received a single gavage dose while the second received 3 daily doses.

Remarks:

Doses / Concentrations:
2.0 g/kg of triethylene glycol

No. of animals per sex per dose / concentration:

2 rabbits/dose level

Control animals:

not specified

Positive control reference chemical:

No data.

Details on study design:

Administration of Triethylene Glycol and Excretion by Animals Nonisotopic triethylene glycol was given by stomach tube to New Zealand White female rabbits in 25% W/V aqueous solution. Urine was collected over sodium fluoride as runoff from metabolism cages, and all animals were allowed food and water ad libitum during the course of the experiment. Urine samples were used directly or stored frozen.

Fractionation of Urine after Administration of Nonisotopic Triethylene Glycol
Following administration of triethylene glycol, urine from rabbits was made alkaline to pH 12-13 by addition of sodium hydroxide. The urine was then exhaustively extracted with chloroform as described in the section on control studies. The chloroform extract contained triethylene glycol which was determined calorimetrically. An additional sample was then subjected to acidic hydrolysis as described in the section on control studies. The urine was then made alkaline as above for extraction of total triethylene glycol (free plus that from hydrolysis of any glucuronide ester) by chloroform. Some urine samples were acidified to pH 2-3 and then extracted with chloroform to obtain material, not extractable from alkaline solution, putative 0- (P-hydroxyethyl)oxyethoxyacetic acid, which was converted into a chromatogen by reaction with 3,.5-dinitrobenzoyl chloride for the calorimetric determination.

Vapor Phase Chromatographic Determinati,on of an Acid Derived from the Metabolism of Triethylene Glycol
The chloroform solution obtained by a continuous exhaustive extraction (72 hours) of acidified rabbit urine obtained after administration of triethylene glycol was evaporated to dryness. The residue was transferred to a 50-ml glass-stoppered bottle with the aid of 2 ml of absolute methanol. After addition of 0.2 ml of concentrated hydrochloric acid and 2,2-dimethoxypropane (cf. Lorette and Brown, 1959), the mixture was shaken and allowed to stand at room temperature for 1 hour. An aliquot (0.2 ml) was chromatographed by the preceding procedure for vapor phase chromatographic determination of triethylene glycol in urine. The recorder response was equivalent to 1% by weight of triethylene glycol in the urine (approximately 3 times that obtained from a similar extraction of alkalinized urine). The aqueous residue from extracted alkalinized sample was then acidified to pH l-2 by addition of hydrochloric acid, The acidic solution was then exhaustively extracted with chloroform. The chloroform solution which contained no triethylene glycol was then evaporated and subjected to the esterification procedure (above). The esterified product had a retention time (8.5 minutes) on the Carbowax column which was identical to that of triethylene glycol. In comparison the dimethyl ester of ethylenedioxydiacetic acid had a retention time of 7.5 minutes. The esterified metabolite, collected from the column, and the dimethyl ester showed a similar infrared absorption spectrum. The former, however, showed a strong OH absorption at 2.9 u.
.
Another chloroform solution from the exhaustive extraction of the acidified urine (5 ml) was evaporated and then subjected to esterification with methanol (see above). To the residue obtained by evaporation of the esterification mixture was added 2 ml of acetic anhydride. The mixture was heated to 90 C for one-half hour. An aliquot (0.1 ml) was subjected to chromatography in the Perkin-Elmer Vapor Fractometer equipped with a column Q17 (2 meters packed with Apiezon L on Chromosorb Red). The column was adjusted to 200 C at a helium flow rate of approximately 150 ml/min. The peak at a retention time of 16 minutes, corresponding to acetylated triethylene glycol, indicated a triethylene glycol content corresponding to that obtained by chromatography of the chloroform extract of alkalinized urine. An earlier peak at 10.5 minutes differed from that obtained of an authentic sample of the dimethylester of ethylenedioxydiacetic acid (13 minutes). The peak responses of the acetylated and esterified metabolic triethylene glycol (0.6870 by weight in the urine) and that of the acetylated unmetabolized triethylene glycol of the sample (0.31% by weight in the urine) were in good agreement with the results obtained above on the Carbowax column. Evidence that triethylene glycol was determined as an acetyl derivative and that the metabolite was determined as an acetyl methyl ester was confirmed in experiments in which it was shown that neither triethylene glycol, ethylenedioxydiacetic acid, nor the methyl ester of the metabolite would pass through column Q, even when the temperature was raised to 220C.

References:
LORETTE, N. B., and BROWN, J. H., JR. (1959). Use of acetone dimethyl acetal in preparation of methyl esters. J. Org. Ckem. 24, 261.262.

Details on dosing and sampling:

Rabbits were dosed with 2 g/kg of non-labelled triethylene glycol

Statistics:

No data.

Details on absorption:

No data.

Details on distribution in tissues:

No data.

Details on excretion:

Following the oral administration of triethylene glycol (200 mg/kg) to the rabbit, 34.3% of the dose was excreted in the urine as unchanged triethylene glycol. Following a 2000 mg/kg oral dosey for 3 consecutive days, an average of 27.3% (calorimetric analysis) of the total dose was excreted as TEG.

Metabolites identified:

yes

Details on metabolites:

After oral doses of triethylene glycol the rabbit excreted triethylene glycol in both unchanged and oxidized form. The data suggest that one of the oxidation products is a monocarboxylic acid which arises by metabolic oxidation of a single terminal hydroxyl group of the parent glycol.

Bioaccessibility (or Bioavailability) testing results:

No data.

Following the oral administration of triethylene glycol (200 mg/kg) to the rabbit, 34.3% of the dose was excreted in the urine as unchanged triethylene glycol as determined by the calorimetric method (Table 1).  In a similar experiment another animal received a 2000 mg/kg dose orally for 3 consecutive days. The calorimetric analysis gave an average value of 27.3% of the total dose excreted. By vapor phase chromatography the value was 28%.

As shown in Table 1, hydrolysis of the urine did not increase the calorimetric value for triethylene glycol determined on a chloroform solution obtained from extraction of the hydrolyzate which had been made alkaline. Triethylene glycol was chemically identified from the chloroform extract as the bis(3,S-dinitrobenzoyl) ester.

A sample of the foregoing urine which had been exhaustively extracted under alkaline conditions was acidified to pH 2 by addition of hydrochloric acid. The sample was then exhaustively extracted with chloroform. The chloroform extract was subjected to the dinitrobenzoyl calorimetric determination.  The transmittance reading corresponded to 17.3% of the administered triethylene glycol.

TABLE 1

EXCRETION OF TRIETHYLENE GLYCOL AND METABOLITES FOLLOWING ADMINISTRATION TO NEW ZEALAND WHITE FEMALE RABBITS

Animal weight (kg)	Dose (g/kg)	Per cent of dose recovered as triethylene glycol^c	Per cent of dose recovered as "hydroxyacid'
2.5	2.0^a	34.3	---
2.8	2.0^b	26.0	35.2^e
		28.6
		28.3^d

^a Urine was collected for 24 hours following administration of a single oral dose.

^b An oral dose of 2.0 g was given daily for 3 consecutive days, Urine was collected during this and a subsequent 3-day period.

^c Colorimetric determinations on chloroform extractions from alkalinized urine.

^d Urine was subjected to acidic hydrolysis prior to alkalinization and subsequent chloroform extraction.

^e Value obtained by subtracting triethylene glycol value from calorimetric determination of total alcohols in chloroform extract of acid-hydrolized acidic urine, assuming that “hydroxyacid” chromatogen possesses one-half the extinction coefficient of dihydroxy compounds such as triethylene glycol.

Conclusions:

Interpretation of results (migrated information): no bioaccumulation potential based on study results
After oral doses of triethylene glycol the rat and the rabbit excrete triethylene glycol in both unchanged and oxidized form. The data suggest that one of the oxidation products is a monocarboxylic acid which arises by metabolic oxidation of a single terminal hydroxyl group of the parent glycol.

Executive summary:

After oral doses of triethylene glycol the rabbit excreted triethylene glycol in both unchanged and oxidized form. The data suggest that one of the oxidation products is a monocarboxylic acid which arises by metabolic oxidation of a single terminal hydroxyl group of the parent glycol.

Description of key information

Components ofthe reaction mass of 2,2'-(ethylenedioxy)diethanol and 3,6,9,12,15-pentaoxaheptadecane-1,17-diol and 3,6,9,12-tetraoxatetradecane-1,14-diol are expected to behave like the individual components studied. Absorption, distribution, metabolism, and excretion data for components of the reaction mass of 2,2'-(ethylenedioxy)diethanol and 3,6,9,12,15-pentaoxaheptadecane-1,17-diol and 3,6,9,12-tetraoxatetradecane-1,14-diol are described.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

20

Absorption rate - inhalation (%):

100

Additional information

Absorption:

Higher ethylene glycols are completely and rapidly absorbed in animals from the gastrointestinal tract due in part to their complete solubility in water and low molecular weights. Likewise, the absorption estimate via inhalation route will be assumed as 100 percent. Dermal bioavailability of ethylene glycols is much lower; at maximum 20% absorption rate assumed based on diethylene glycol (DEG) data. For dermally applied DEG, 47.2, 32.6, 29.2 and 16.8% was retained after 15 minutes, 64 minutes, 8 hours and 24 hours, respectively (Dow, 1981). After 15 minutes of dermal contact with DEG, a radioactive peak appeared at ~ 112 microns into the layer of the skin indicating rapid absorption via dermal route. Alternatively, another in vivo rat percutaneous penetration study with DEG demonstrated 9% urinary excretion up to 71 hours (Mathews et al., 1991).

Distribution, Bioaccumulation Potential:

Since ethylene glycol substances are completely soluble in water, they are expected to be well distributed throughout the aqueous tissues of the body and have no or low concentrations in adipose tissue. For DEG, the apparent volume of distribution was determined at 1 ml/g; DEG and its metabolites did not accumulate in tissues. Therefore, ethylene glycol components are considered to have no bioaccumulation potential.

Metabolism:

The higher ethylene glycols are linked by stable ether bonds and are not extensively metabolized in the body. The main pathway for metabolism of the ethylene glycol analogues is oxidation via alcohol dehydrogenases and aldehyde dehydrogenases however, the majority of ethylene glycol analogues will be either unchanged or conjugated with glucuronide. The potential for metabolic oxidation of ethylene glycols decreases with increasing number of oxyethylene units per molecule as seen experimentally from in vitro derived Vmax and Km kinetic values.

In rat, oxalic acid is not a significant DEG metabolite and metabolism becomes saturated at higher doses. In both the rat and the rabbit, TEG showed a high degree of urinary excretion of unchanged compound, in addition to small amounts of monocarboxylic acid arising by metabolic oxidation of the terminal hydroxyl group on the parent glycol as well as glucuronide conjugation. The results in vivo agree with DEG and TEG agree with the in vitro metabolism data via aldehyde dehydrogenase, indicating the decreased potential for metabolic oxidation with increasing number of oxyethylene repeat units per molecule. Based on in vitro data, TTEG and pentaEG are expected to be oxidized to a lesser extent than TEG and either excreted unchanged or as glucuronide conjugates of the parent glycols. The low order of excretion of radioactivity by way of respiratory carbon dioxide demonstrated that the cleavage of carbon bonds of the administered TEG occurred to only a limited extent. Respiratory carbon dioxide in the rat constituted only 1% of the radioactive TEG dose and most of this activity appeared during the first 12-hour period after administration. 1.5-7.2% of DEG was eliminated as exhaled carbon dioxide in the rat and dog. The evidence suggests that metabolic cleavage of the ether linkages and formation of ethylene glycol wound not be important events in the metabolism of TTEG and pentaEG.

Excretion:

The excretion of ethylene glycols is rapid with the urine being the major excretory route in the rat and rabbit. Animal studies indicate a high degree of urinary excretion of unchanged TEG in addition to the excretion of oxidized glycol acid metabolite. In rat and dog, DEG and its metabolites were primarily eliminated in urine (73-96%) whereas 1.5-7.2% was eliminated as exhaled carbon dioxide and 0.7-2.2% with the feces; the urinary excretion followed first order kinetics with elimination half-lives of 3.6 hours. After doses of 5 mL/kg and 10 mL/kg ¹⁴C

-DEG, semi-logarithmic plots of elimination rate versus time were constant for 5 and 9 hours, respectively, indicating that DEG accelerated its renal elimination by inducing osmotic diuresis (Heilmair et al., 1993). >85% of the orally administered TEG to rats was recovered within 24 hours. 86.1 - 94.0% of the administered dose was recovered within 5 days in the urine. Approximately 95% of the recovered radioactivity, or 90% of the ¹⁴C dose, appeared in the urine with lesser amount in the feces. The total elimination of radioactivity (in urine, feces, and expired air) during the 5-day period following a single oral dose in rat was 91-98%. For dermally applied DEG, in contact with the rat skin for 8 and 24 hours, 12 and 32.2% of the radioactivity was identified in the urine, respectively; and also 9% urinary excretion up to 72 hours (Mathews et al., 1991).