Ethylene di(S-thioacetate)

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Based on the read-across hypothesis, GDMA is expected to show similar effects in a developmental/reproduction toxicity screening assay. Therefore, after correction for molecular weight, the NOAEL for parental toxicity as well as for female reproductive performance was determined to be 37 mg/kg bw/day, while the NOAEL for progeny was calculated as 74 mg/kg bw/day.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Justification for type of information:

This scenario covers the analogue approach for which the read-across hypothesis is based on (bio) transformation to common compound(s). For the REACH information requirement under consideration, the effects obtained in a study conducted with one source substance are used to predict the effects that would be observed in a study with the target substance if it were to be conducted. The same type of effect(s) or absence of effect is predicted. The predicted strength of the effects may be similar or based on a worst-case approach
The hypothesis corresponds to Scenario 1 of the RAAF. The source substance NaTG will be used to read-across two endpoints, e.g. repeated dose toxicity and toxicity to reproduction, of the target substance GDMA. Source and target substance are expected to share common metabolites. GDMA is rapidly hydrolysed after absorption into TGA and ethylene glycol, while NaTG will dissociate into TGA and sodium ion. By now, no experimental toxicokinetic data is available for GDMA. Therefore, simulated gastric acid hydrolysis as well as in vitro metabolic studies are planned to strengthen the hypothesis.
For detailed information, please refer to section 13.2.

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEL

Effect level:

37 mg/kg bw/day (actual dose received)

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

mortality

Remarks on result:

other: corrected for molecular weight differences

Dose descriptor:

LOAEL

Effect level:

74 mg/kg bw/day (actual dose received)

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

mortality

Remarks on result:

other: corrected for molecular weight differences

Critical effects observed:

no

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

74 mg/kg bw/day (actual dose received)

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

viability

Remarks on result:

other: corrected for molecular weight differences

Dose descriptor:

LOAEL

Generation:

F1

Effect level:

147 mg/kg bw/day (actual dose received)

Based on:

act. ingr. (dissolved fraction)

Sex:

male/female

Basis for effect level:

viability

Remarks on result:

other: corrected for molecular weight differences

Critical effects observed:

no

Reproductive effects observed:

not specified

Conclusions:

Based on the read-across hypothesis, GDMA is expected to show similar effects in a developmental/reproduction toxicity screening assay. Therefore, after correction for molecular weight, the NOAEL for parental toxicity as well as for female reproductive performance was determined to be 37 mg/kg bw/day, while the NOAEL for progeny was calculated as 74 mg/kg bw/day.

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

37 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

The available key study is reliable (Klimisch 1) and was conducted according to OECD 421

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

Screening for developmental/reproduction toxicity:

A study according to OECD 421 is available for NaTG.

Four groups of 12 male and 12 female Sprague-Dawley rats received sodium thioglycolate). Administration was performed daily, by oral (gavage) administration, 10 weeks before mating and through mating and, for the females, through gestation until day 5 post-partum, at dose-levels of 0, 20, 40 or 80 mg/kg bw/day. The No Observed Adverse Effect Level (NOAEL) for parental toxicity was considered to be 20 mg/kg/day based on deaths at 40 and 80 mg/kg/day. Male reproductive performance was not affected by treatment with sodium thioglycolate. Dosing at 40 and 80 mg/kg/day resulted in deaths in late gestation associated with delayed delivery and a No Observed Effect Level (NOEL) for female reproductive performance was therefore set at 20 mg/kg/day.

The NOEL for toxic effects on progeny was set at 40 mg/kg/day, based on the dead litter at 80 mg/kg/day.

A proper evaluation of the reproductive performance of females given 80 mg/kg/day was not possible because of the numerous deaths observed in this group in the peri-natal period.

No experimental data is available for GDMA. Based on the read-across hypothesis, similar effects as for NaTG would be expected for GDMA:

Table 7: Developmental/reproductive toxicity of non-common compounds.

	CAS	NOAELs
Ethylene glycol	107-21-1	3 generation reproductive toxicity study NOAEL fertiliy and reproduction = >1000 mg/kg bw/day (rats, no effects observed) (DePass ,1986)
Sodium	7440-23-5	Not classified as reproductive toxicant (WHO, 2003)

 

As demonstrated in Table 7 the non-common compounds do not contribute to a relevant extent to the overall acute toxicity of the substances. The main driver for toxicity of the substances seems to be the TGA moiety.

Data gaps were identified for GDMA in dermal and/or inhalation toxicity. Based on the considerations concerning bioavailability, there is reason to believe that NaTG could be the worst-case for GDMA. Data obtained with NaTG was applied to GDMA and corrected for molecular weight differences. The estimated NOAEL for female fertility and parental toxicity was determined to be 37 mg/kg bw/day, while the NOAEL for reproductive toxicity was determined to be 74 mg/kg bw/day. The NOEL for male fertility was determined to be >147 mg/kg bw/day.

Effects on developmental toxicity

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

For the assessment of prenatal developmental toxicity, data are available from ATG, NaTG, GMT, 2-EHTG, MMP, PETMP, TLA, and E12. A justification for read-across is attached to IUCLID section 13.

 

In the dose range finding study for the prenatal developmental toxicity test with ATG mortality was observed at 100 mg/kg bw/d and above (3/5 females at 100 mg/kg bw/d, 5/5 females at 150 mg/kg bw/d died). At 100 mg/kg bw/d, the surviving animals had a lower terminal body weight. Increased fetal loss and a lower fetal body weight were observed at 100 mg/kg bw/d, both considered secondary to maternal toxicity.

Based on these results, the dose levels for the prenatal developmental toxicity study with ATG were selected (3, 15, 75 mg/kg bw/d). At the high dose, 2/25 animals died; a cause of death could, however, not be established. All animals of the high dose showed rooting in the bedding material for about 15 min after dosing.

No effects on body weight development, food or water consumption were observed in any dose group. A slightly, but not significantly, lower uterus weight in the high dose females was considered to be incidental. Treatment with ATG had no effects on the numbers of corpora lutea, implantations, live fetuses, dead fetuses, or complete/early/late resorptions. Fetal weights and sex distribution were comparable to control. There was no increase in the frequency of malformations in any dose group. NOEL(embryo-fetal toxicity) = 75 mg/kg bw/d; NOEL(maternal toxicity) = 15 mg/kg bw/d.

 

In the reproduction/developmental toxicity screening test with NaTG (0, 20, 40, 80 mg/kg bw/d) mortality was observed in the high dose (2 males + 6 females; one further female sacrificed due to dead pups) and mid dose (1 female). There were no treatment related effects estrous cyclicity, time to mating, pregnancy index. Females given 80 mg/kg bw/d had a significantly longer gestation period (22.8, p<0.01,vs.21.6 days), a non-significantly lower number of corpora lutea (mean of 6.7, ns,vs.8.5) and a significantly lower number of implantations (10.3, p<0.001,vs.16.5) and pups (9.0, p<0.01,vs.14.7). One female had total resorptions and one litter died on day 1post-partum. There were no treatment-related pup clinical signs or necropsy findings. Pups treated at 40 or 80 mg/kg bw/d had higher mean body weight gains than the controls between day 1 and day 5 post-partum. There were no effects of treatment on sperm morphology, motility or counts. The mean absolute seminal vesicle weights were statistically significantly lower for all male groups in a dose-related manner (absolute weights were -17%, -19% and -35% at 20, 40 and 80 mg/kg/day, respectively). This correlated with a slight decrease in secretory content in the seminal vesicles observed at microscopic examination of the males given 80 mg/kg/day. In the absence of atrophy of seminal epithelium at microscopic examination, these minor findings were not considered to be adverse.

Male reproductive performance was not affected by treatment with NaTG. Dosing at 40 and 80 mg/kg bw/d resulted in deaths in late gestation associated with delayed delivery. NOEL(female reproductive performance) = 20 mg/kg bw/d, NOEL(toxic effects on progeny) = 40 mg/kg bw/d

 

In the 2-generation reproduction toxicity test with NaTG (0, 10, 20, 40 mg/kg bw/d) 40 mg/kg bw/d had no effect on non-pregnant, naïve, adult rats but that it causes maternal toxicity and death of susceptible pregnant females around the time of delivery.

Effects on the dam include lack of nesting/nursing behavior and this causes death of

the pups which have been delivered. If treatment is stopped just prior to delivery, the females may survive delivery but pup death may still occur and pup clinical signs of coldness suggest that maternal nesting/nursing behavior is still impaired by treatment with the test item and affect pup survival. There is evidence that female rats are more affected by test item treatment than males as shown by lower F1 female body weight and body weight gain.

Minimal to moderate periportal heptocellular microvacuolation was observed in females and some male F0 animals treated at 40 mg/kg bw/d suggestive of mild hepatotoxicity. There were no effects on sperm parameters in the control or high-dose group males of either generation. There were no effects of treatment on any parameters measured in either males or females with the test item at 10 or 20 mg/kg bw/d.

The small effects observed on pup survival at 40 mg/kg bw/d may have been secondary to the severe and lethal effects observed in the pregnant dams at that dose-level.

NOEL(parental toxicity, female fertility and gestation, development, growth and survival of the progeny) = 20 mg/kg bw/d

NOEL(male fertility, female mating behavior) >/= 40 mg/kg bw/d

 

Two prenatal developmental toxicity studies with dermal administration of NaTG are available, one in rat (0, 50, 100, 200 mg/kg bw/d) and one in rabbit (0, 10, 15, 25, 65 mg/kg bw/d). Feed consumption was increased in the absence of increased maternal body weights at 50 and 100 mg/kg/day, and in the presence of reduced maternal body weights at 200 mg/kg/day, in rats. There was no effect of treatment in rabbits in maternal body weight, weight changes during gestation, or feed consumption. There was a clear increase in incidence and severity of both erythema and edema at the site of application in all treated groups. Embryo/fetal development was not adversely effected in either species, except for reduced fetal body weight at the high dose in the rat study. In rats, there was also a significant dose-related upward trend for percent fetuses with skeletal variations per litter, and for percent males, but not females, with variations per litter. This was due to slightly increased incidences of extra or rudimentary ribs on Lumbar I and of dumbbell cartilage and bipartite ossification in thoracic centra (both very common skeletal variations in term rat fetuses). These fetal variations, in combination with the absence of teratogenic alterations and with reductions in maternal and fetal weight, are interpreted as secondary to intrauterine growth retardation resulting from maternal toxicity (Tyl, 2003).

 

In the combined repeated dose toxicity study with the reproduction/developmental toxicity screening testwith GMT (0, 15, 50, 150 mg/kg bw/d),5 females at 150 mg/kg bw/d died, the cause for death not being evident from histopathology. No effects were observed on mating, offspring litter size and viability, development, clinical signs of the offspring. The NOEL for reproductive effects in males was 150 mg/kg bw/d as assessed by the absence of adverse effects on fertility or on testicular weight and histopathology. Due to the high maternal mortality and toxicity at 150 mg/kg bw/d in the females, which precluded reproductive assessment at that dose level, the NOEL for reproductive toxicity in females is 50 mg/kg bw/d.

 

In the reproduction/developmental toxicity screening test with 2-EHTG (0, 10, 50, 150 mg/kg bw/d) 3 males and 3 females died in the high dose group. No test item-related effects on male and female mating and fertility indices, male copulation index or female conception index, the mean number of days between pairing and coitus, mean gestation lengths, mean numbers of corpora lutea, implantation sites were observed. Mean live litter size in the high dose was reduced in a test item-related manner. Postnatal survival in this group was reduced on PND 0-1 and birth to PND 4, due in part to 1 female with total litter loss on PND 1. Mean male and female pup body weights and body weight gains in the 150 mg/kg/day group were reduced. Several of these pups were also noted as being small. Mean live litter size and postnatal survival in the low and mid dose were unaffected by test item administration. There were no test article-related effects on the general physical condition of the pups or pup body weights in the 10 and 50 mg/kg/day groups. At the necropsy of pups that were found dead, there were no internal findings that were related to parental treatment with the test item. NOAEL(reproductive, developmental, systemic, neonatal toxicity) = 50 mg/kg bw/d

 

In the combined repeated dose toxicity study with the reproduction/developmental toxicity screening test with MMP (0, 25, 50, 100 mg/kg bw/d) no treatment-related effects on precoital time, fertility indices, mean duration of gestation, number of implantations, postimplantation loss, pup survival or litter size from birth through to scheduled sacrifice on day 4 post partum, mean number of corpora lutea per dam were observed. No abnormal findings were noted for pups at first litter check or during the first 4 days post partum. No effects were noted on sex ratios, mean pup weights on day 0 and day 1 post partum, mean pup weight development during the first 4 days post partum. The NOEL for reproduction/developmental toxicity was considered to be 100 mg/kg bw/d.

 

In the prenatal developmental toxicity study with PETMP (0, 50, 120, 300/200 mg/kg bw/d), the high dose dams showed clinical signs (occasional body tremors, clonic convulsions, hunched posture, ataxia, lethargy, pilo-erection, splayed gait and, labored respiration and decreased respiratory rate), reduced body weight, reduced body weight gain, reduced food consumption and slightly lower gravid uterus weight (though not statistically significant). The maternal NOEL is 120 mg/kg bw/day. 

Lower mean male fetal weight, increased incidence of fetuses showing incomplete ossification of the thoracic centrum or less than four ossified caudal vertebrae, increased incidence of absent renal papilla were observed in the high dose in the presence of marked general toxicity in dams. The developmental NOEL is 120 mg/kg bw/day.

 

In prenatal developmental toxicity studies in rat, mouse, hamster, and rabbit, no adverse effects with respect to number of implantations and maternal or fetal death were noted after oral administration of E12 up to the highest dose level (1600 mg/kg bw/d in rat, mouse, and hamster; 1000 mg/kg bw/d in rabbit). There were no significant differences in numbers of abnormalities of the soft or skeletal tissues between the treated and control fetuses.

 

Summary

With the exception of the mercaptan family, data on prenatal developmental toxicity are available for all subgroups.

 

None of the substances showed developmental toxicity or teratogenicity.

 

The effects observed in thereproduction/developmental toxicity screening test and the 2-generation reproduction toxicity test with NaTG consisting of a significantly longer gestation period, a non-significantly lower number of corpora lutea, a significantly lower number of implantations and reduced pup survival were only seen in the presence on severe maternal toxicity including mortality and thus, secondary effects.

In a comparable manner, mean live litter size, postnatal survival and pup body weights and body weight gains were reduced in the high dose groups of thereproduction / developmental toxicity screening test with 2-EHTG in the presence of marked general toxicity (mortality).

 

Also, the increase infetal variations observed in the dermal prenatal developmental toxicity test with NaTG (slightly increased incidences of extra or rudimentary ribs on Lumbar I and of dumbbell cartilage and bipartite ossification in thoracic centra - common skeletal variations in term rat fetuses), is interpreted as secondary to intrauterine growth retardation resulting from maternal toxicity, especially in combination with the absence of teratogenic alterations and with reductions in maternal and fetal weight.

 

Similar effects were seen for the members of the 3-MPA family. Lower mean male fetal weight, increased incidence of fetuses showing incomplete ossification of the thoracic centrum or less than four ossified caudal vertebrae, increased incidence of absent renal papilla were observed in the prenatal developmental toxicity study with PETMP in the high dose in the presence of marked general toxicity in dams.

 

E12 caused no developmental toxicity in rat, mouse, hamster, and rabbit.

 

Overall, it can be stated, that this whole group of substances as described inTable1(IUCLID chapter 13)has a very low potential to cause reproductive or developmental toxicity. Effects (e.g., lower fetal weight,intrauterine growth retardation,reduced postnatal survival) were observed only in the presence of severe general maternal toxicity.

 

Based on the available data, this group of substances does not need to be classified for developmental toxicity.

 

For better comparison, the NO(A)ELs have been recalculated on the basis of S-content, which is assumed to be the main driver for toxicity:

 

Overall comparison of NO(A)ELs(developmental toxicity) to S-content.

Family	Substance (study)	NO(A)EL [mg/kg bw/d]	S in molecule [%]	Related to S-content [mg/kg bw/d]
ATG	ATG (NOEL, OECD TG 414, oral: gavage, rat)	75	32.1	24.1
TGA	NaTG (NOAEL, OECD TG 416, oral: gavage, rat)	20	30.7	6.1
	GMT (reproduction NOEL, OECD TG 422, oral, rat)	50	21.1	10.5
	2-EHTG (reproduction NOAEL, OECD TG 421, oral: gavage, general toxicity, rat)	50	17.1	8.6
3-MPA	MMP (reproduction NOAEL, OECD TG 422, oral: gavage, rat)	100	29.1	29.2
	PETMP (developmental NOAEL, OECD TG 414, oral: gavage, rat)	120	7.2	8.6
Intra-molecular-Sulfur	E12 (developmental NOAEL, OECD TG 414, oral: gavage, rat, mouse, hamster, rabbit)	>/=1600	6.8	108.8

 

After adjustment to S-content, the NOAELs of most of the substances were within the same order of magnitude. Using the lowest NOAEL obtained in the 2-generation reproduction toxicity study conducted with NaTG is considered to be an appropriate starting point for DNEL derivation. Remaining uncertainties due to read-across can be adequately considered by applying an additional assessment factor.

 

References

Arkema, 2010. Two-generation reproduction toxicity study by oral route (gavage) in rats. Unpublished report. CIT 35047 RSR

 

Bruno Bock, 2010b. Reproduction/developmental toxicity screening test by oral route (gavage) in rats. Unpublished report. CIT 30721 RSR

 

Bruno Bock, 2015c. PETMP: Oral (Gavage) Pre-Natal Development Toxicity Study in the Rat.Unpublished report. Harlan41401135

 

Merck, 1998a. Toxicology – Study report – Reproductive toxicity. Ammonium thioglycolate - dose finding embryo-fetal toxicity study with oral administration to rats. Unpublished report. Merck T9412

 

Merck, 1998b. Toxicology – Study report – Reproductive toxicity. Embryo-fetal toxicity study with oral administration of Ammonium thioglycolate to rats. Unpublished report. Merck T9413

 

Thioesters Association, 2001a. IUCLID data set for 3,3’-thiodipropionic acid, didodecyl ester, submission to US EPA

 

Thioesters Association, 2001b. IUCLID data set for 3,3’-thiodipropionic acid, dioctadecyl ester, submission to US EPA

 

Thioesters Association, 2005. 2-Ethylhexyl mercaptoacetate [CAS No. 7659-86-1]: a reproduction/developmental toxicity screening study in rats. Unpublished report. WIL-528002

 

Thioesters Association, 2007a. Glyceryl thioglycolate 80%: oral (gavage) combined repeat dose toxicity study with reproduction/developmental toxicity screening test in the rat. Unpublished report. SPL 2207/0003

 

Thioesters Association, 2007b. Methyl 3-Mercaptopropionate: Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test in the Rat. Unpublished report. RCC A74698

 

Tyl RW et al., 2003.Developmental Toxicity Evaluation of Sodium Thioglycolate Administered Topically to Sprague–Dawley (CD) Rats and New Zealand White Rabbits. Birth Defects Research (Part B) 68:144–161 (2003)

Justification for classification or non-classification

Overall, mercaptoacetic acid and its salts and esters are not considered to be developmental or reproductive toxicants, except at dose levels associated with maternal lethality.

Maternal mortality was observed in the OECD 421 and OECD 416 studies in rats at doses of 40 and 80 mg/kg bw/day. The acute oral LD50 of sodium mercaptoacetate (NaTG) is 50 – 200 mg/kg bw in fasted animals and the lethal doses in the reproductive toxicity studies fall into this range.

Thus, the mortalities of pregnant dams cannot be regarded as reproductive toxicity, but rather a direct consequence of the established toxic mode of action of mercaptoacetates. Mercaptoacetates are known inhibitors of mitochondrial fatty acid β-oxidation. Studies with NaTG have shown that hypoglycaemia occurs in rats dosed with NaTG via oral gavage and that this effect is pronounced in fasted compared to non-fasted animals (Grosdidier 2011, Report No. 37043, IUCLID Section 7.9.4). The hypoglycaemia is a result of impaired gluconeogenesis secondary to inhibition of fatty acid catabolism by mercaptoacetate. Ad-libitum feeding, as employed in the OECD 421 and OECD 416 studies, apparently saves the animals from succumbing already after a single gavage dose by providing a sufficient external glucose supply. Maternal death in NaTG treated dams occurred in late pregnancy (GD 21-23) or early after parturition (PND 1-2). It is likely that the enhanced energy demand due to parturition and / or lactation further exhausts the glucose reserve of the dams ultimately contributing to their death.

A classification as toxic to reproduction is not justified since all maternal and foetal/offspring effects are directly related to the observations leading to a classification as Acute Tox 3 – H301: Toxic if swallowed.