2-ethylhexyl 10-ethyl-4,4-dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

 No effect on reproductive organs or reproductive capacity was observed up to and including the highest dose tested

Link to relevant study records

Reference

Endpoint:

two-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP Guideline study (OECD 416). Justification for read-across : Is on the basis that Dioctyltin bis(IOMA) and dioctyltin bis(2-EHMA) are isomers of the same compound and are structural analogues of each other. Based on the recently conducted developmental toxicity studies in two species it is considered that DOTI is likely to be more toxicoligically active and therefore use of data on this substance would be considered to be a worst case assessment of the registered substance.

Qualifier:

according to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Rats (Sprague-Dawley [Tif:RAIf (SPF)] obtained from Lippische Versuchstierzucht Hagemann GmbH.
Animals were individually caged (except during mating) and maintained at a temperature of 22 +/- 2 deg. C, a relative humidity of 50 +/- 15%, and a
12-h light/12-h dark photoperiod (~150 lux).

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

no

Details on mating procedure:

not reported

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

Duration of dosing of F0 generation
males - 10 weeks prior to mating, during mating (3 weeks), and post mating until sacrifice;
females - 10 weeks prior to mating and during mating.
Mated females continued to receive test diets during gestation and lactation; unmated females received test diets until sacrifice. Test diets were prepared weekly and analyzed for homogeneity and stability.

Duration of dosing of F1 generation:
males - 14 weeks (starting at the end of lactation prior to mating), during mating (3 weeks), and post mating until sacrifice;
females - 14 weeks (starting at the end of lactation prior to mating) and during mating (3 weeks).

Frequency of treatment:

continuously (in diet)

Remarks:

Doses / Concentrations:
20, 60, and 200 ppm
Basis:
nominal in diet

No. of animals per sex per dose:

25 male/25 female Rats per group

Control animals:

yes, concurrent no treatment

Details on study design:

no

Positive control:

no

Parental animals: Observations and examinations:

Animal behavior and general condition were observed daily. Food consumption was recorded at 2-3 day intervals. Body weights were measured weekly.
The following parameters were determined: mean pre-coital time, mean duration of pregnancy, number of pups (live and dead), sex of pups, number of stillbirths, number of runts, number of pups with malformations, and pup body weights.
All animals, including pups, were necropsied (males and dams after weaning; pups on day 22, except those used as parents for the subsequent generation). The number of implantation scars on the endometrium was recorded in all parental females. Uteri of non-pregnant females were examined.

Oestrous cyclicity (parental animals):

no

Sperm parameters (parental animals):

no

Litter observations:

Functional tests (mid-air righting reflex, auditory startle reflex, and pupillary reflex) were performed on all pups. Morphological examinations (pinna detachment, ear opening, eye opening, testicular descent, and vaginal opening) were recorded for all pups.

Postmortem examinations (parental animals):

The following organs and tissues were collected and examined from all parental animals: all gross lesions, ovary, uterus, cervix, vagina, testis, epididymis, seminal vesicle with coagulation gland, prostate, spleen, thymus, iliac lymph node, mammary gland, pituitary, adrenals, and thyroids. Organs and tissues were examined histopathologically.

Postmortem examinations (offspring):

The following organs and tissues were collected and examined from one male and one female pup from each F1 and F2 litter at necropsy: spleen, thymus, iliac lymph node. The following organ weights were recorded in all parental F0 and F1 animals: ovary, uterus, testis, pituitary, adrenals, thyroid, spleen, thymus, iliac lymph node. The following organs weights were recorded in one male and one female pup from each F1 and F2 litter: spleen, thymus, iliac lymph node. Organs and tissues were examined histopathologically.

Statistics:

no data

Reproductive indices:

no data

Offspring viability indices:

no data

Clinical signs:

no effects observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Reproductive function: oestrous cycle:

not specified

Reproductive function: sperm measures:

not specified

Reproductive performance:

effects observed, treatment-related

No substance-related mortality or changes in behavior or external appearance.
Body weights were comparable to the control group.
The absolute food consumption of female rats in the 200 ppm dose group was lower than the controls (-6% on lactation days 7-14, -9% on lactation days 14-21). Concentrations of 20 and 60 ppm in the diet did not influence the reproduction parameters. However, at 200 ppm in the diet, there was a slight increase in pup mortality, and a significant difference in the viability index at day 4 of lactation and in the lactation index after 21 days lactation.
The body weight of pups from dams treated with 200 ppm test substance was significantly decreased for males and females after 14 and 21 days lactation. Functional tests and morphological landmarks revealed no substance-related findings at 20 and 60 ppm in the diet.
At 200 ppm, vaginal opening was slightly delayed. No substance-related pathological findings were observed. Organ weights at 20 ppm were comparable to the control. At 60 ppm, parental males had a slightly decreased relative thymus weight. At 200 ppm, the relative thymus weights of males and females were significantly decreased.
The incidence of thymic involution was significantly increased in males at 200 ppm. No substance-related pathological findings were observed.

Dose descriptor:

NOAEL

Effect level:

20 ppm

Sex:

male/female

Basis for effect level:

other: based on a reduction in the relative thymus weight of males

Clinical signs:

no effects observed

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

No substance-related mortality, changes in behavior, or in external appearance.  At 20 and 60 ppm, body weights were comparable to controls.  
At 200 ppm in the diet, the body weight of males was significantly lower during the pre- and post-mating phase.  The body weight of females at 200 
ppm was comparable to the control.  There was a significant reduction in food consumption of females at 200 ppm during lactation.  
Concentrations of 20 and 60 ppm in the diet did not influence the reproduction parameters.  

At 200 ppm, there was an increase in the number of stillbirths (26 vs. 5 in the control group). There was a slight increase in stillbirths at 60 ppm.
At 200 ppm in the diet, pup mortality increased during lactation; the viability index decreased (82.0% vs. 85.7% controls); pup body weight decreased; pinna unfolding and eye and ear opening were slightly delayed; and there was a slight increase in the number of negative findings of the auditory startle reflex. No substance-related pathological findings were observed.
At 60 ppm, there was a slight decrease in the relative thymus weights; significant for females only. At 200 ppm, the relative thymus weights were significantly decreased in both sexes, and the relative spleen weight of females was significantly decreased. F2 generation: Organ weights were comparable to the control group. No histopathological changes were observed. No teratogenic effect was observed.

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

20 ppm

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Reproductive effects observed:

not specified

Conclusions:

The NOAEL for a DOT(IOMA)/MOT(IOMA) mixture was 20 ppm for the F0 parental generation (effects on thymus weight) and for the F1 generation the NOAEL was 20 ppm (based on a decrease in relative thymus weights in male and female pups, a slight decrease in the relative thymus weight of males and an increase in stillbirths at 60 ppm). No teratogenic effects were observed.

Executive summary:

An OECD Guideline 416 (Two-Generation Reproduction Toxicity Study) was carried out with the mixture Dioctyltin bis(IOMA) [CAS No. 26401-97-8]:Octyltin tris(IOMA) [CAS No. 26401-86-5] (78.8:16.9% mixture); Rats were exposed to 20, 60 and 200 ppm in the diet . An untreated control group was tested concurently. Various general toxicological parameters were studied as well as reproductive/developmental observations of parent animals and off-spring.

Under the experimental conditions, the NOAEL for the F0 parental generation was 20 ppm (~1.5 mg/kg bw/d), based on a reduction in the relative thymus weight of males at 60 ppm. No substance-related pathological findings were observed.

The NOAEL for the F1 generation until weaning was 20 ppm (~1.6 mg/kg bw/d), based on a decrease in relative thymus weights in male and female pups at 60 ppm. The NOAEL for the F1 generation post lactation was 20 ppm, based on a slight decrease in the relative thymus weight of males and an increase in stillbirths at 60 ppm. No teratogenic effect was observed.

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

1.5 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

The available study was conducted under GLP conditions and in accordance with a standardised guideline. Since the study was conducted with a mixture of the registered substance, Dioctyltin bis(IOMA) [CAS No. 26401-97-8] and Octyltin tris(IOMA) [CAS No. 26401-86-5] (78.8:16.9% ), rather than with the substance, as such, the study is regarded as a read-across data and was subsequently assigned a reliability score of 2 in line with the criteria of Klimisch (1997). Read-across is justified on the basis that Dioctyltin bis(IOMA) and dioctyltin bis(2-EHMA) are isomers of the same compound and are structural analogues of each other. Based on the recently conducted developmental toxicity studies in two species it is considered that DOTI is likely to be more toxicoligically active and therefore use of data on this substance would be considered to be a worst case assessment of the registered substance. The overall quality of the database is regarded as high.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

In the two generation study performed under GLP and according to OECD 416 (1997), the mixture Dioctyltin bis(IOMA)[Cas No. 26401 -97 -8] :Octyltin tris(IOMA)[Cas No. 26401 -86 -5] (78.8:16.9%) were administered to the F0 generation 10 weeks prior to mating, during mating (3weeks) and post-mating. The F1 generation were treated 14 weeks during premating, 3 weeks during mating. Females continued to receive the test material during gestation and lactation. The following treatment-related effects were observed : F0 generation: 

- Mortality: 1 male died at 200 ppm diet

- Absolute food consumption reduced in females at 200 ppm diet (-6% on lactation days 7-14, -9% on lactation days 14-21)

- Viability index slightly reduced at 200 ppm (96.2% vs. 98.6% in the controls).

- Lactation index significantly decreased at 200 ppm diet (88.6% vs. 94.4% in controls) after 21 days lactation.

- Slight increase in pup mortality at 200 ppm diet.

- Pup body weights significantly decreased at 200 ppm diet in both sexes after 14 and 21 days lactation.

- Slight delay in vaginal opening at 200 ppm diet.

- Slight decrease in relative thymus weight in males at 60 ppm diet; significant decrease in relative thymus weight in both sexes at 200 ppm diet.

- Increased incidence of thymic involution at 200 ppm diet (significant for males only).

- Microscopic examination of the organs found no substance-related changes.

F1 generation:

- No mortality.

- Body weight: significant reduction in males at 200 ppm diet.

-Food consumption: reduced in females at 200 ppm diet; significant on lactation days 14-21.

-Increased number of stillbirths at 200 ppm diet (26 vs. 5 in controls).

- Viability index: decreased at 200 ppm (82.0% vs. 95.7% in controls).

- Pup mortality: increased at 200 ppm diet from day 4-21 of lactation.

- Lactation index: decreased at 200 ppm diet (82.3% vs. 94.4%).

- Pup body weight: significantly reduced at 200 ppm for males and females on days 4, 7, 14, and 21 of lactation.

- Morphological changes: pinna unfolding, eye and ear opening were slightly delayed at 200 ppm diet.

- Relative thymus weight: significantly decreased in males and females at 200 ppm diet and at 60 ppm for females only

- Relative spleen weight: significantly decreased in females at 200 ppm diet.

- Increased incidence of thymic involution at 200 ppm (significant for males).

The NOAEL for F0 males and females was 20 ppm diet (approx. 1.5 mg/kg bw/day) based on a slightly reduced relative thymus weight for males at 60 ppm (approx. 4.4 mg/kg bw/day). 

The NOAEL for the F1 generation was 20 ppm diet (approx. 1.6 mg/kg bw/day), based on a reduction in relative thymus weights for males and females at 60 ppm diet (approx. 4.7 mg/kg bw/day).

No teratogenic effects were observed in this study.

Short description of key information:
A two-generation study (1997) was performed using mixture of DOT(isooctythioglycolate, (CAS No. 26401-97-8)/Octyltin tris (IOMA) (CAS No. 26401-86-5)) (78.8:16.9% mixture). Dioctyltin bis (IOMA) and dioctyltin bis (2-EHMA) are isomers of the same compound and are structural analogues of each other. Based on the recently conducted developmental toxicity studies in two species it is considered that DOTI is likely to be more toxicoligically active and therefore use of data on this substance would be considered to be a worst case assessment of the registered substance.

Under the experimental conditions of this two generation study, the NOAEL for the F0 parental generation was 20 ppm (~1.5 mg/kg/bw), based on a reduction in the relative thymus weight of males at 60 ppm. The NOAEL for the F1 generation until weaning was 20 ppm (~1.6 mg/kg/bw/d), based on a decrease in relative thymus weight in male and female pups at 60 ppm. The NOAEL for the F1 generation post-lactation was 20 ppm, based on a slight decrease in the relative thymus weight of males and an increase in stillbirth at 60 ppm.

Justification for selection of Effect on fertility via oral route:
Only one study is avaiable.

Effects on developmental toxicity

Description of key information

> Key Studies
- Mouse
The NOAEL for maternal toxicity was determined to be 15 mg/kg based on a biologically relevant depression in thymus size at the 30 mg/kg dose. However, no treatment-related effects were noted in any of the developmental toxicity parameters investigated; therefore the NOAEL for developmental toxicity was concluded to be 60 mg/kg, the highest dose tested.
- Rabbit
The NOAEL for maternal toxicity was determined to be 20 mg/kg based on a biologically relevant depression in thymus weight at the 80 mg/kg dose. However, no treatment-related effects were noted in any of the developmental toxicity parameters investigated; therefore the NOAEL for developmental toxicity was concluded to be 80 mg/kg, the highest dose tested.
> Supporting Study
The NOAEL for maternal toxicity and embryofetal development  in the rat study were set at 5 mg/kg/day (based on decrease in maternal body weight gain and increase in the percentage of dead fetuses at 25 mg/kg/day). 

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 August 2014 to 11 November 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or methodological deficiencies, which do not affect the quality of the relevant results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

mouse

Strain:

Swiss

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: In-house bred animals
- Age at study initiation: 10 - 12 weeks
- Weight at study initiation (GD 0): 24.01 - 33.20 g
- Housing: during the pre-mating period a maximum of three animals were housed in a standard polypropylene cage (290 x 220 x 140 mm) with stainless steel mesh top grill. Clean sterilised paddy husk was provided as bedding material. During the mating period two mice (one male and one female) were housed together until confirmation of mating (GD 0) at which point the females were housed individually in polypropylene cages and males were housed with their former cage mates.
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.6 - 23.1 °C
- Humidity (%): 50 - 59 % (relative)
- Air changes (per hr): 12 - 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light

Route of administration:

oral: gavage

Vehicle:

peanut oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test material was administered by oral gavage in peanut oil at a dose volume of 5 mL/kg bw. Control animals received vehicle only at a dose volume of 5 mL/kg bw.
Fresh dosing solutions were prepared daily before administration.

VEHICLE
- Justification for use and choice of vehicle: Peanut oil was selected since it has been utilised in previous toxicology studies with related test materials and is a routinely used vehicle.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Formulation analysis was conducted to enable verification of dose concentration by analysing total tin content. Analyses were conducted during week 1 and week 2 of the dosing period. The dose samples were collected in duplicate (2 x 5 mL) for each dose formulation including vehicle control. One set of samples were analysed while the other set was stored and analysed later, if required.

Details on mating procedure:

- Impregnation procedure: Cohoused
- If cohoused:
- M/F ratio per cage: 1 male / 1 female
- Length of cohabitation: Until copulation was confirmed or for 2 weeks (maximum)
- Proof of pregnancy: Vaginal plug and/or vaginal smear, referred to as day 0 of pregnancy

Females not mated within 14 days of pairing with the first male were placed with a second proven male if presence of sperm in the vaginal smear and/or vaginal plug was not confirmed.

Duration of treatment / exposure:

Females received test material daily from gestation day 5 to gestation day 17 (inclusive).

Frequency of treatment:

Daily throughout treatment period.

Duration of test:

Dams were sacrificed on gestation day 18.

No. of animals per sex per dose:

25 pregnant females per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Doses were selected upon consideration of the following available data.
In a published report of an oral gavage developmental toxicity study in mice [Faqi, 2001] with a closely related dioctyltin material [dioctyltin isooctyl thioglycolate; DOT[IOTG]; DOTI], the test material utilised had approximately 80 % dioctyl and 20 % monooctyl components. Doses were 20, 30, and 45 mg/kg body weight [Phase I], and 67 and 100 mg/kg body weight [Phase II]. Dosing was done from gestation day 6 [GD6; day of vaginal coital plug = GD1] to gestation day 17 [GD17]. Caesarean sections were done on GD18.
Adjusted maternal weight gain [GD18 weight minus GD1 weight minus gravid uterine weight] at the 100 mg/kg dose was 56 % of the control. High variability in the maternal weight data, as evidenced by the high SD of the mean, obscured the statistical significance of this biologically relevant maternally toxic outcome. One maternal death occurred at this dose further supporting the fact that this is a maternally toxic dose. The maternal weight effect was accompanied by a statistically significant decrease in maternal thymus weight. Maternal liver weight, on both an absolute and relative basis, was also statistically significantly decreased at this dose.
Relative to the control mice, maternal thymus weight and liver weight trended downward at 67 mg/kg, suggesting that this dose is an upper bound in order to preclude an unacceptable level of maternal toxicity and generate a valid assessment of developmental toxicity in a new study.
The number of dams maintaining pregnancy in the treated groups up to the 45 mg/kg dose was not different from controls. The number of implantation sites, number of viable foetuses, and foetal weight were unaffected by treatment. There was a suggestion of an increase in the number of resorptions at 45 mg/kg, but this was a not statistically significant and the number of viable foetuses was comparable to controls at this dose.
The number of dams maintaining pregnancy in the control group for Phase II of the study was decreased relative to all other groups in the study. The number of dams maintaining pregnancy in the 67 and 100 mg/kg groups was not statistically different than the Phase II control. As noted above, the 67 mg/kg dose appears to be the upper bound dose for a developmental toxicity study because foetal weight at the 67 mg/kg dose is significantly less than controls, the number of resorptions is increased, and the number of resorptions per implantation is statistically significantly increased.
There is evidence of foetal toxicity, expressed as delayed ossification, at 45 mg/kg and higher which further supports 67 mg/kg as an upper bound for any further investigation of developmental toxicity.
In the study reported by Henninghausen, (1979) a single intramuscular dose of dioctyltin chloride [DOTC] at 60 mg/kg reduced thymus weight to 48 % of controls and thymocyte count to 64 % of controls. A single oral gavage dose of 300 mg/kg resulted in thymus weight at 65 % of controls and thymocyte count at 70 % of controls. The repeated-dose test paradigm for developmental toxicity studies makes it highly unlikely that pregnancy in mice could be sustained.
Therefore, the high dose chosen for this study is 60 mg/kg, to reflect a dioctyltin dose with minimal maternal and foetal toxicity as the upper bound. It is anticipated that this dose will meet the developmental toxicity test guideline criteria of producing some maternal toxicity without compromising the survival of the pregnant dam, the integrity of pregnancies to Day 18, or the survival of the developing foetuses.
The low dose chosen (15 g/kg) was selected to reflect the NOEL in the published study.

- Rationale for animal assignment: Each day the body weight of mated mice was recorded. The mated females were distributed to all groups based on their body weights so as to maintain comparable mean body weights across all groups.

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: animals were observed twice daily for mortality and morbidity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: animals were observed once daily for clinical signs of toxicity.

BODY WEIGHT: Yes
- Time schedule for examinations: Dams were weighed on gestation days 0, 3, 5 and daily thereafter up to, and including, gestation day 18.

FOOD CONSUMPTION: Yes
- Time schedule: individual feed intake of mated females was recorded on gestation days 0 - 3, 3 - 5, 5 - 7, 7 - 9, 9 - 11, 11 - 14, 14 - 17, and 17 - 18.

WATER CONSUMPTION: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 18
All the animals were sacrificed on gestation day 18 by carbon dioxide exposure and subjected to detailed gross pathology. At necropsy the thymus was excised, weighed and placed in 10 % formalin for possible future histopathological examination.

Ovaries and uterine content:

The ovaries and uterine content were examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Number of live and dead foetuses: Yes

Fetal examinations:

- External examinations: Yes
- Soft tissue examinations: Yes
- Skeletal examinations: Yes
- Head examinations: Yes

Other examinations included:
- Sex, number and weight of live foetuses
- Crown rump length (measured after sacrifice)

Statistics:

Raw data was subjected to computer statistical processing. One-way ANOVA with Dunnett's post test was performed for data (body weight, food consumption, number of corpora lutea, uterus weight, number of implantations, number of live foetuses, body weight of live foetuses), using SPSS software. All analyses and comparisons were evaluated at the 95 % level of confidence (P<0.05).

Indices:

Corrected body weight (g) = (Gestation day 18 body weight – Gestation day 5 body weight) – Gravid uterus weight
Pre-implantation loss (%) = ((Number of corpora lutea – Number of implants)/Number of corpora lutea) x 100
Post-implantation loss (%) = ((Number of implants – Number of viable foetuses)/Number of Implants) x 100
Male/Female sex ratio = Number of live male foetuses/Number of live female foetuses
Male/female foetuses (%) = (Number of live male foetuses/Total number of foetuses) x 100 or (Number of live female foetuses/Total number of foetuses) x 100
Foetal incidence (%) = (Number of foetuses with a particular observation/Total number of foetuses in a group) x 100

Details on maternal toxic effects:

Maternal toxic effects:yes. Remark: Reduction in thymus weight at 30 mg/kg

Details on maternal toxic effects:
MATERNAL DATA
- Clinical Signs of Toxicity and Morbidity/Mortality
The animals did not reveal any clinical signs of toxicity and mortality at any of the tested doses throughout the experiment.
- Maternal Body Weight
There were no statistically significant differences in maternal body weights across the dose groups on any single gestation day. However, there was a clear dose-related pattern of reduced body weights beginning after GD6, the first day of dosing, and continuing for the duration of the study. The high dose was the most severely affected, though a dose-related decrement relative to the control body weights can be seen across all doses particularly from GD16 to GD18. At 30 mg/kg the maternal weight effect was marginal, but maternal body weight gain in the 60 mg/kg high dose group was 11.5 % [uncorrected] and 26.6 % [corrected] less than the vehicle control, a clear adverse effect. The corrected body weight gain in the low (15 mg/kg) and mid (30 mg/kg) dose groups were -16.7 % and - 17.7 % when compared to the controls.
- Feed Consumption
No treatment related differences in average feed consumption were observed at any dose.
- Gross Pathology [Maternal]
There was a treatment-related macroscopic finding of reduced maternal thymus weight.
The mean maternal thymus weight was statistically significantly reduced in the 30 mg/kg [mid] and 60 mg/kg [high] dose groups. The mean maternal thymus weight in the low dose mice was reduced relative to controls, but was not statistically significant. These observations are indicative of a treatment-related specific target organ toxicity resulting from exposure to the test material. No other gross pathological findings were noted in any dose group.

PREGNANCY DATA
A total number of 21 (84 %), 21 (84 %), 20 (80 %) and 20 (80 %) mated females were confirmed pregnant at the time of caesarean section for groups G1, G2, G3 and G4, respectively.

UTERINE OBSERVATIONS
There were no statistically significant differences in these gravid uterus weights, number of implantation sites, pre- and post-implantation loss or early or late resorptions across dose groups when compared to the vehicle control.

REPRODUCTION DATA
No treatment related effects were noted in mean gravid uterus weight, no. of corpora lutea, no. of implantations in all the groups, no. of early or late resorptions and percentage of post implantation loss.
There were no statistically significant differences in the sex ratio, mean litter size or the number of live foetuses per dam across dose groups when compared to the vehicle control.

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Dose descriptor:

LOAEL

Effect level:

30 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
FOETAL DATA
- Foetal Weight
The mean foetal weights [combined sexes] were 1.35, 1.37, 1.30 and 1.31 grams for groups G1, G2, G3 and G4, respectively. Mean foetal weights were not statistically significantly different across the dose groups when compared to controls.

- External Examination
No external abnormalities were noted during gross examinations of foetuses at any dose.

- Visceral Examination
No treatment-related abnormalities were observed during visceral examinations of foetuses at any dose. The noted findings [pale coloured kidneys and dilated renal pelvis] are common findings for foetuses of this species and strain. The observations were not dose dependent, nor was the severity of the anomaly increased with dose. This result supports the conclusion that the findings are incidental and that the test material did not produce an adverse effect during foetal development of the soft tissues.

- Skeletal Examination
The noted anomalies (poorly ossified frontal, parietal and inter-parietal bones; ossification site at first lumbar vertebrae; supplementary ribs) are common findings for foetuses of this species and strain. These morphologic observations did not occur in a dose-dependent pattern, nor was the severity of the anomaly increased with dose. The findings were therefore considered to be incidental, and not indicative of a teratogenic effect.

- Crown-rump length
The average crown-rump lengths were 23.2, 24.0, 23.3 and 22.9 mm for groups, G1 through G4, respectively. There were no statistically significant differences in length across all dose groups when compared to the control.

Remarks on result:

not determinable due to adverse toxic effects at highest dose / concentration tested

Abnormalities:

not specified

Developmental effects observed:

not specified

Dose Formulation Analysis

The results for chemical homogeneity and dose concentration verification are within the acceptance limits of ± 10 % of the nominal concentrations.

Table 1: Maternal Body Weights (g)

Dose Group (mg/kg)	Gestation Day
	0	3	5	6	7	8	9	10	11	12	13	14	15	16	17	18
G1: 0	27.41	28.25	29.03	29.49	30.06	30.54	31.41	32.68	34.03	35.59	37.52	39.34	41.31	43.81	46.23	49.10
G2: 15	27.08	27.71	28.33	28.90	29.59	30.21	30.74	31.73	33.20	34.80	36.73	38.81	41.12	43.96	46.02	48.21
G3: 30	27.23	28.11	28.67	29.20	29.59	30.42	31.04	32.24	33.72	35.13	36.80	38.76	40.78	43.35	45.71	48.17
G4: 60	26.93	27.69	28.58	29.12	29.52	30.11	30.74	31.74	33.06	34.61	36.15	37.81	40.15	42.63	44.30	46.35

 

Table 2: Maternal Body Weight Gain

Dose Group (mg/kg)	GD 5-18 (g)	GD 5-18 (% of control)	GD 5-18 (% gain compared to control)
G1: 0	20.07	100.0	0.0
G2:15	19.18	95.6	-4.4
G3: 30	19.5	97.2	-2.8
G4: 60	17.77	88.5	-11.5

 

Table 3: Litter Data

Dose Group	No. of Corpora Lutea (mean)	Implantation Sites (mean)	Live Foetuses (mean)	No. of Early Resorptions (mean)	No. of Late Resorptions (mean)	Mean Pre-implantation Loss (%)	Mean Post-implantation Loss (%)
G1: 0	10.1	10.1	10.1	0.0	0.0	0.0	0.0
G2: 15	10.7	10.7	10.1	0.1	0.0	0.0	0.9
G3: 30	10.7	10.6	10.5	0.1	0.1	0.5	1.5
G4: 60	10.0	10.0	9.7	0.1	0.2	0.0	2.6

 

Group & Dose (mg/kg)	Mean Thymus weight (g)
G1 (0 mg/kg)	0.0400
G2 (15 mg/kg)	0.385
G3 (30 mng/kg)	0.0306*
G4 (60 mg/kg)	0.0260*

* p < 0.05

 

Table 4: Summary of Foetal Examinations

Parameters	Group (Dose mg/kg)	G1 (0 mg/kg)	G2 (15 mg/kg)	G3 (30 mg/kg)	G4 (60 mg/kg)
External Examinations
Malformations	No. of foetuses	0	0	0	0
	%	0.0	0.0	0.0	0.0
Variations	No. of foetuses	0	0	0	0
	%	0.0	0.0	0.0	0.0
Visceral Examinations
Malformations	No. of foetuses	0	0	0	0
	%	0.0	0.0	0.0	0.0
Variations	No. of foetuses	4	5	3	6
	%	4.0	4.8	3.0	6.5
Skeletal
Malformations	No. of foetuses	0	0	0	2
	%	0.0	0.0	0.0	2.0
Variations	No. of foetuses	6	3	2	9
	%	5.4	2.6	2.0	8.8

 

Conclusions:

Under the conditions of the study the NOAEL for maternal toxicity was determined to be 15 mg/kg based on a biologically relevant depression in thymus size at the 30 mg/kg dose. However, no treatment-related effects were noted in any of the developmental toxicity parameters investigated; therefore the NOAEL for developmental toxicity was concluded to be 60 mg/kg, the highest dose tested.

Executive summary:

The purpose of this study was to assess the effects of prenatal exposure of pregnant female Swiss mice and their developing foetuses to the test material when administered by oral gavage in a peanut oil vehicle at 5 mL/kg to the mated females from gestation day [GD] 5 to 17. In life examinations included checks for mortality and clinical signs of toxicity, body weight measurements and an evaluation of food consumption. All the animals were sacrificed on gestation day 18 by carbon dioxide exposure and subjected to detailed gross pathology; the gross pathology included a determination of thymus size. The gravid uterus was collected by hysterectomy and foetuses were removed by caesarean section. Foetuses were subjected to external, soft tissue and skeletal examination.

No deaths were observed during the experimental period and there were no clinical signs recorded which were indicative of overt toxicity. There were no statistically significant differences in maternal body weights across the dose groups on any single gestation day. However, there was a clear dose-related pattern of reduced body weights beginning after GD6, the first day of dosing, and continuing for the duration of the study. The high dose was the most severely affected and a dose-related decrement relative to the control body weights can be seen across all doses particularly from GD16 to GD18. At 30 mg/kg the maternal weight effect was marginal, but maternal body weight gain in the 60 mg/kg high dose group was 11.5 [uncorrected] and 26.6 % [corrected] less than the vehicle control, a clear adverse effect. There was a treatment-related macroscopic finding of reduced maternal thymus weight.

The mean maternal thymus weight was statistically significantly reduced in the 30 mg/kg [mid] and 60 mg/kg [high] dose groups. The mean maternal thymus weight in the low dose mice was reduced relative to controls, but was not a statistically significant difference. No other gross pathological findings were noted in any dose group.

No treatment related effects were noted in mean gravid uterus weight, no. of corpora lutea, no. of implantations in all the groups, no. of early or late resorptions and percentage of post implantation loss.

No external abnormalities were noted during gross examinations of foetuses at any dose and no treatment-related abnormalities were observed during visceral examinations of foetuses at any dose.

Therefore, under the conditions of the study the NOAEL for maternal toxicity was determined to be 15 mg/kg based on a biologically relevant depression in thymus size at the 30 mg/kg dose. However, no treatment-related effects were noted in any of the developmental toxicity parameters investigated; therefore the NOAEL for developmental toxicity was concluded to be 60 mg/kg, the highest dose tested.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

15 mg/kg bw/day

Study duration:

subacute

Species:

mouse

Quality of whole database:

Two developmental toxicity studies were conducted with the substance itself, the studies are regarded as key studies; they were performed under GLP conditions and in accordance with strandardised guideline OECD 414. The key studies were assigned a reliability score of 1 in line with the criteria of Klimisch (1997). A single study is included as supporting information; the study was conducted with a mixture of Dioctyltin bis(IOMA) [CAS No. 26401-97-8]:Octyltin tris(IOMA) [CAS No. 26401-86-5] (80:20%). Information on the mixture is considered to be suitable for read across since DOT(2-EHMA) and DOT(IOMA) are isomers of the same compound and are structural analogues of each other. Based on the recently conducted developmental toxicity studies in two species it is considered that DOTI is likely to be more toxicoligically active and therefore use of data on this substance would be considered to be a worst case assessment of the registered substance.


The supporting study was performed under GLP conditions and followed a method similar to that which is outlined in the standardised guidelines and was subsequently assigned a reliability score of 2. The overall quality of the database is high.

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

Two key studies, investigating the developmental toxicity of the registered substance itself, are available; one study was conducted in mice and the other in rabbits. Both studies were performed under GLP conditions and in accordance with the standardised guideline OECD 414.

 

The purpose of the mouse study was to assess the effects of prenatal exposure of pregnant female Swiss mice and their developing foetuses to the test material when administered by oral gavage in a peanut oil vehicle at 5 mL/kg to the mated females from gestation day [GD] 5 to 17. In life examinations included checks for mortality and clinical signs of toxicity, body weight measurements and an evaluation of food consumption. All the animals were sacrificed on gestation day 18 by carbon dioxide exposure and subjected to detailed gross pathology; the gross pathology included a determination of thymus and liver size. The gravid uterus was collected by hysterectomy and foetuses were removed by caesarean section. Foetuses were subjected to external, soft tissue and skeletal examination.

No deaths were observed during the experimental period and there were no clinical signs recorded which were indicative of overt toxicity. There were no statistically significant differences in maternal body weights across the dose groups on any single gestation day. However, there was a clear dose-related pattern of reduced body weights beginning after GD6, the first day of dosing, and continuing for the duration of the study. The high dose was the most severely affected and a dose-related decrement relative to the control body weights can be seen across all doses particularly from GD16 to GD18. At 30 mg/kg the maternal weight effect was marginal, but maternal body weight gain in the 60 mg/kg high dose group was 11.5 [uncorrected] and 26.6 % [corrected] less than the vehicle control, a clear adverse effect. There was a treatment-related macroscopic finding of reduced maternal thymus weight.

The mean maternal thymus weight was statistically significantly reduced in the 30 mg/kg [mid] and 60 mg/kg [high] dose groups. The mean maternal thymus weight in the low dose mice was reduced relative to controls, but was not a statistically significant difference. No other gross pathological findings were noted in any dose group.

No treatment related effects were noted in mean gravid uterus weight, no. of corpora lutea, no. of implantations in all the groups, no. of early or late resorptions and percentage of post implantation loss.

No external abnormalities were noted during gross examinations of foetuses at any dose and no treatment-related abnormalities were observed during visceral examinations of foetuses at any dose.

Therefore, under the conditions of the study the NOAEL for maternal toxicity was determined to be 15 mg/kg based on a biologically relevant depression in thymus size at the 30 mg/kg dose. However, no treatment-related effects were noted in any of the developmental toxicity parameters investigated; therefore the NOAEL for developmental toxicity was concluded to be 60 mg/kg, the highest dose tested.

 

The purpose of the rabbit study was to assess the effects of prenatal exposure of pregnant female New Zealand White rabbits and their developing foetuses to the test material when administered by oral gavage in a peanut oil vehicle at 2 mL/kg to the mated females from gestation day [GD] 6 to 28. In life examinations included checks for mortality and clinical signs of toxicity, body weight measurements and an evaluation of food consumption. All the animals were sacrificed on gestation day 29 by iv injection of sodium thiopentone and subjected to detailed gross pathology; the gross pathology included a determination of thymus weight. The gravid uterus was collected by hysterectomy and foetuses were removed by caesarean section. Foetuses were subjected to external, soft tissue and skeletal examination.

No deaths or abortions were observed during the experimental period and there were no clinical signs recorded which were indicative of overt toxicity and there were no treatment related differences in average feed consumption or body weights observed at any dose. A total number of 19 (79 %), 21 (88 %), 19 (79 %) and 20 (83 %) mated females were confirmed pregnant in groups G1, G2, G3 and G4, respectively. Gross necropsy revealed a treatment-related effect on the thymus. The mean maternal thymus weight was reduced 5.1, 9.6, and 12.8 % in the 4 mg/kg [low], 20 mg/kg [mid], and 80 mg/kg [high] dose groups, respectively. No other gross pathological findings were noted in any dose group.

Investigation of reproduction parameters revealed no treatment related effects in any of the following: mean gravid uterus weight, number of corpora lutea, number of implantation sites, number of early or late resorptions, percentage of pre and post implantation loss, sex ratio, mean litter size, foetal weight or the number of live foetuses per doe across all the groups.

The mean foetal weights [combined sexes] were 36.6, 37.3, 35.5, and 32.3 grams for groups G1, G2, G3 and G4, respectively. Mean foetal weights were not statistically significantly different across the dose groups when compared to controls. However, at the high dose the mean foetal body weight is -11.9 % relative to controls which suggests a biologically-relevant, but marginal effect on foetal maturation. This however, was found to be disproportionately affected by a single litter in this group who had low body weights. The other litters in this group did not follow the same trend.

Foetal crown-rump length was statistically significantly different from the controls in the highest dose group. This result was affected by one litter in this group who had disproportionately low crown-rump lengths when compared to the other litters of this group. In addition, there were no correlating statistically significant differences for any other developmental parameter.

No external abnormalities were noted during gross examinations of foetuses at any dose and no treatment-related abnormalities were observed during visceral examinations of foetuses at any dose.

Therefore, under the conditions of the study the NOAEL for maternal toxicity was determined to be 20 mg/kg based on a biologically relevant depression in thymus weight at the 80 mg/kg dose. However, no treatment-related effects were noted in any of the developmental toxicity parameters investigated; therefore the NOAEL for developmental toxicity was concluded to be 80 mg/kg, the highest dose tested.

 

Supporting information is available in the form of an embryotoxicity and teratogenicity study which was conducted with a read across material, which was a mixture of Dioctyltin bis(IOMA) [CAS No. 26401-97-8]:Octyltin tris(IOMA) [CAS No. 26401-86-5] (80:20% mixture). Read across is considered justified on the basis DOT(2-EHMA) and DOT(IOMA) are isomers of the same compound and are structural analogues of each other. Based on the recently conducted developmental toxicity studies in two species it is considered that DOTI is likely to be more toxicologically active and therefore use of data on this substance would be considered to be a worst case assessment of the registered substance.

 

In this study dams were treated with mixture of DOT (IOTG) and MOT(IOTG) (80:20%) at 1, 5 and 25 mg/kg/day during day 6 -15 of gestation. Alopecia was observed in single animals of all four groups and was not attributed to treatment. There was a slight (non-significant) decrease in corrected body weight and corrected body weight gain from day 6 to day 21 at 25 mg/kg/day dose.  This reduction was attributed largely to one single dam. There was a statistically significant increase in the percentage of dead foetuses at 25 mg/kg/day. However, the seven dead foetuses concerned only one litter.  Though clear-cut effects were found in only one dam in 25 mg/kg/day dose group, the test substance was considered to induce marginal maternal toxicity at 25 mg/kg/day. The dose-level without maternal and/or embryofoetotoxicity was 5 mg/kg/day (equivalent to 0.77 mg Sn/kg b.w/day).

 

Disregarded studies

Two additional studies have been included in the substance dataset for the purpose of completeness however, both studies have been disregarded and the results from those studies are not included in the overall assessment of the developmental toxicity of the registered substance.

 

The study reported by Faqi (2001) failed to fulfil the requirements of a GLP OECD 414 guideline study since detailed information on the following were not included: maternal body weight, food consumption, housing, dosing, analysis of the dosing formulations or individual animals data. Furthermore, no information was given on foetal sex ratio, foetal weight per sex or internal malformations and no comparison to historical control data was carried out. The study was therefore considered to be deficient and the results are not taken forward for hazard classification.

 

The study reported by Battenfeld (1992) was also disregarded since it was not possible to interpret the results of the study based on the information presented in the study report. During the study maternal disease was reported; the disease that is described in the report is common in rabbits of the age and strain used in the study. It was not possible to ascertain whether maternal effects which were observed resulted from the disease or from treatment with the test material since detailed examination of the immune system are not included in developmental toxicity studies and were not included as part of this study. There was one case of torticollis, a symptom of encephalitozoonosis, a parasitic disease occurring in immunodeficient animals, which was reported. Since no effects were seen in the rangefinder study, at doses up to 30 mg/kg bw/day, the maternal findings observed in the main study were considered spurious. Overall the study was considered to be deficient and the results are not taken forward for hazard classification.

Justification for selection of Effect on developmental toxicity: via oral route:
Two devlopmental toxicity studies have been conducted using the substance itself as test material. The mouse study has been selected since the mouse was found to be the more sensitive species, generating the lower NOAEL.

Toxicity to reproduction: other studies

Additional information

Together with the data outlining the toxicological, endocrine and reproductive properties of dioctyltin compounds, two additional studies with Dichlorodioctylstannane (dioctyltin dichloride) are included for completeness since the substance was initially considered to be a relevant substance to use for read-across purposes since findings from a gastric hydrolysis study showed that DOT(2-EHMA) was readily hydrolysed to Dichlorodioctyltilstanane (CAS no.3542-36-7) under physiological conditions (see section 7.1.1). Thus DOTC(Dichlorodioctylstannane) was considered to be an appropriate anchor compound and surrogate for the mammalian toxicology endpoints of repeated dose, in vivo genetic toxicity, reproduction and developmental effects, when it is dosed via the oral route of administration.

Read-across to the substance DOTC is no longer considered as wholly appropriate based on the results of the recent Hydrolysis study, as reported by Naßhan, H, 2014 (see section 7.1.1) which indicate the substance DOTECl is the only metabolite of DOTE which is formed in a simulated mammalian gastric environment; no dioctyltindichloride was formed under the conditions of the study. The studies with DOTC have therefore been disregarded in the overall assessment of the registered substance with regards to reproductive and developmental toxicity.

Justification for classification or non-classification

There are no data to suggest that classification of the substance for either reproductive or developemental toxicity is required.

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No. 1272/2008 (CLP), the substance does not require classification with respect to either reproductive or developemental toxicity.

In accordance with the criteria for classification as defined in Annex VI, Directive 67/548/EEC (DSD), the substance does not require classification with respect to either reproductive or developmental toxicity.