Dioctyltin oxide

Endpoint summary

Description of key information

ORAL
Key study:- Waalkens-Berendsen (2004), OECD 422, NOAEL 5 mg/kg diet (based on the effects noted in the thymus) equivalent to 0.3-0.4 mg/kg bw/day for male animals and 0.3-0.5 mg/kg bw/day for female animals.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

5 November 2003 to 8 March 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was conducted in accordance with the standardised testing guideline OECD 422 and in accordance with GLP with no deviations thought to affect the quality of the presented data. The study was reported to a high standard, sufficient to assess the reliability of the data presented.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 10-11 weeks
- Weight at study initiation: The weight variation of the animals for each sex did not exceed 20 %.
- Diet: ad libitum
- Water: tap water ad libitum in polypropylene bottles

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-25 °C
- Humidity (%): 30-70 5
- Air changes (per hr): 10 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours light and 12 hours dark

DOSE-RANGE FINDING TEST IN-LIFE DATES: From: 12 November 2003 To: 26 November 2003
MAIN TEST IN-LIFE DATES: From: 14 January 2004 To: 8 March 2004

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): The experimental diets were prepared once shortly before the study
- Mixing appropriate amounts with (Type of food): The test substance was weighed and placed in a small grinder. The tray was rinsed with food which was then also added to the grinder and mixed for 2 x 30 seconds. This mixture was moved to a Stephan cutter and the grinder was rinsed with food and moved to the cutter. Approximately 3 kg weighed food was mixed into the cutter for 2 x 2 minutes and moved. This was then moved to the Lödige cutter. The Stephan cutter was rinsed with approximately 3 kg of food and that was also moved to the Lödige cutter. Mixing was continued in the Lödige cutter for 2 minutes with the total amount of food.
- Storage temperature of food: <-18 °C

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The feed was checked for homogenous distribution, stability and concentration of the test substance for all the doses in the dose-range finding study. The same dose preparation for the dose-range finding study was also used for the main test. The homogenous distribution and achieved concentration of the low dose in the main test was also analysed.

Directly after preparation of the diet for the dose-range finding study, samples for homogeneity and stability were taken. Five samples were taken (approximately 50 g each) to examine the homogeneity of the dose from the top centre, middle centre, bottom centre, left centre and right centre of the mixer. Secondly samples (around 50 g) were taken from the top centre part of the mixer to measure the stability. The samples taken for measurement of the homogeneity were also used for dose confirmation. In addition the content (achieved concentration) of the test substance in the batch of diet used in the main study. Diet samples were taken for analysis immediately after preparation and stored at – 18 °C.

Samples of the 0, 25, 75, 200 and 500 mg/kg diets from the dose-range finding study and doses of 0, 25 and 250 mg/kg from the main study as well as all related calibration samples were derivatised.

A calculated amount of internal standard solution (MHT, DHT and TTPT in methanol) was added to 2.0 g of diet in a 50 mL Corning tube. 10 mL of 100 % acetic acid was then added and the Corning tube was closed and shaken for 60 minutes (250 rpm). 10 mL of acetate buffer solution (pH 4.5) was added along with 10 mL methanol. 2.0 mL of 20 % (m/V) aqueous STEB solutions was added, followed by 10 mL hexane (containing naphthalene, approximately 0.1 mg/L). The tube was shaken for 15 minutes (250 rpm) then placed in an oven at 60 °C for 15 minutes. After phase separation, the hexane layer (approximately 3 mL) was removed and washed with 3 mL of 2 mol/L HCl (30 minutes shaking at 250 rpm). The hexane top layer was diluted with hexane: hexane extracts from sample with dose levels of 0, 25 and 75 mg/kg were diluted five times, the higher doses were diluted fifty times. The resulting solutions were transferred into an amber coloured glass vial and anaylysed using GC-MS.

The procedure for the samples from the main study at doses of 0 and 5 mg/kg followed the same derivatisation procedure, except the initial quantity of the diet was 5.0 g not 2.0 g

The concentration of organotin compounds in the extracts was determined using GC-MS. For calculation of the amount of DOTO in the samples, the peak area of DHT was used as an internal standard. Quantitiation was achieved using the calibration graphs constructed from the calibration solutions.
The following conditions were used:
- Column: Fused silica HP5 MS, 30 m, 0.25 mm ID, 0.25 µm film
- Precolumn: fused silica HP5 MS, 2.5 m, 0.25 mm ID, 0.25 µm film
- Column temperature: after 3 minutes at 45 °C at a rate of 5 °C/min to 80 °C; then at a rate of 15 °C/min to 260 °C; 15 min at 260 °C.
- Carrier: helium; 1.5 mL/min constant flow
- Injection volume: 1 µL
- Injection temperature: start at 60 °C, then at a rate of 14.5 °C/s to 300 °C; 5 min at 300 °C
- Injection method: splitless
- Ionisation: electron impact 70 eV
- Mass range: 60-600 amu
- Mass fragments used: DOT m/z = 375*; 263; 151, DHT 347*; 249; 179
Mass fragments marked with an asterisk were used for quantitation

Duration of treatment / exposure:

28 days (treated food was available ad libitum)

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
Range finding study: 0, 25, 75, 200 and 500 mg/kg diet
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
Main study: 0, 5, 25 and 250 mg/kg diet
Basis:
nominal in diet

No. of animals per sex per dose:

22 males and 22 females in the dose range finding study (5 groups of 4 male and 4 female rats)
52 males and 52 females in the 14-day main study (4 groups of 12 male and 12 female rats)

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: Doses were selected on the results of the range finding test
- Rationale for animal assignment: Randomised

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Every morning throughout the study, and a second observation in the afternoon of working days.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Prior to the first exposure and then once weekly

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights of male and female rats were taken on day -2 (randomisation) and on days 0 (first day of dosing), 7 and 13 of the premating period.
Males were weighed weekly during the mating period until sacrifice. Females were weighed during mating (day 0, 7 and 13) and mated females were weighed on day 0, 7, 14 and 21 during presumed gestation and on day 1 and 4 of lactation. All animals were weighed at sacrifice.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, also calculated as g/animal/day

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of the premating period
- Anaesthetic used for blood collection: Yes, CO2/02 anaesthesia
- Anti-coagulant: K2-EDTA
- Animals fasted: Yes, overnight
- How many animals: 5 rats/sex/group
- Parameters checked:
Haemoglobin
Packed cell volume
red blood cell count
reticulocytes
Total white blood cell count
Prothrombin time
Thrombocyte count
Mean corpuscular volume (MCV)
Mean corpuscular haemoglobin (MCH)
Mean corpuscular haemoglobin concentration (MCHC)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of the premating period
- Anaesthetic used for blood collection: Yes, CO2/02 anaesthesia
- Animals fasted: Yes, overnight
- How many animals: 5 rats/sex/group
- Parameters checked:
Fasting glucose
Alkaline phosphatase activity (ALP)
Aspartate aminotransferace activity (ASAT)
Alanine aminotransferace activity (ALAT)
Gamma glutamyl transferase activity (GGT)
Total protein
Albumin
Ratio albumin to globulin
Urea
Creatinine
Bilirubin (total)
Cholesterol (total)
Triglycerides
Phospholipids
Calcium (Ca)
Sodium (Na)
Potassium (K)
Chloride (Cl)
Inorganic phosphate

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Arena testing was performed prior to the first exposure and then once weekly until the end of dosing and in females until the end of lactation. Males and females selected for the functional observation battery test (FOB) and spontaneous activity measurements were excluded from the final arena testing.
At the end of the study, FOB test and spontaneous motor activity measurements were performed on day 27 for males and on post natal day for for females.
- Dose groups that were examined: All animals were subject to the arena testing. For the other two tests, 5 animals per sex were randomly selected from each dose group.
- Battery of functions tested:
Autonomic: lacrimation, salivation, pupil response to light, palpebral closure, piloerection, defecation and urination
Neuromuscular: gait, mobility, forelimb and hindlimb gripstrength, landing foot splay, righting reflex
Sensorimotor: response to tail pinch, click, tough and approach of a visual object
Convulsive: clonic and tonic movements
Excitability: ease of removal, handling reactivity, arousal and vocalisations
Activity: rearing and motor activity
Physiological: body temperature

OTHER: Reproductive and developmental indices were also examined as part of the test.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
The following were taken from all animals:
Ovaries
Uterus
Testes
Epididymides
Seminal vesicles
Prostate
Organs and tissues showing macroscopic abnormalities

The following were taken from 5 animals/sex/group:
Adrenals
Axillary lymph node
Bone marrow (femur)
Brain
Caecum
Coagulation glands
Colon
Duodenum
Eyes
Heart
Jejunum
Lungs
Kidneys
Liver
Mammary gland (females only)
Mesentric lymph node
Parathyroids
Peyer's patches
Pituitary
Rectum
Sciatic nerve
Spinal cord
Spleen
Stomach
Thymus
Thyroids
Trachea
Urinary bladder

The following organs were weighed:
Adrenals
Brain
Heart
Kidneys
Liver
Spleen
Thymus

HISTOPATHOLOGY: Yes
Microscopic examination was performed on the collected organs of all rats in the control and high-dose group.
The liver and ovaries of females and the thymus of the male and female rats in the low and mid-dose groups were also evaluated
The following tissues, though collected were not subject to histopathological examination:
Coagulation glands
Mammary gland (females only)
In addition, reproductive organs of males that failed to sire (mated female which was not pregnant) and females that were non-mated or non-pregnant of the mid and low dose groups were microscopically examined.

Other examinations:

As part of the developmental screening, gross observations were performed on the pups.

Statistics:

Clinical findings were evaluated using Fisher’s exact probability test.
Bodyweight, bodyweight gain, organ weights and food consumption was assessed by one-way analysis of variance (ANOVA) followed by Dunnett’s multiple comparison tests.
Red blood cell and coagulation variables, total white blood cell counts, absolute differential white blood cell counts, clinical chemistry values and organ weights were assessed by one-way ANOVA followed by Dunnett’s multiple comparison tests (treatment period).
Reticulocytes and relative differential white blood cell counts were assessed using Kriskal-Wallis non-parametric ANOVA followed by Mann-Whitney U-tests.
Histopathological changes were evaluated using Fisher’s exact probability test.
The results of the functional observations were measured on different scales. Continuous measurements were analysed by one-way analysis of variance at each time point, if found to be statistically significant, a post-hoc group comparison was performed. Rank order data were analysed by Kruskal-Wallis analysis of variance at each test time point, followed by planned multiple comparisons between dose groups were a significant results occurred. Categorical data were assessed using Pearson chi-square analysis.
Motor activity data were assessed by one-way analysis of variance at each time point with a post-hoc group comparison performed on significant results.
All tests were two sided and the level of probability p<0.05 was considered to be significant. Effects of treatment on habituation were analysed using repeated measures of analysis variance on time blocks. Each session consisted of 5 time blocks of 6 minutes each.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
One female in the high dose group was found dead on gestation day 24.
One male animal in the high dose group showed exopthalmus from week 2 and complete degeneration of the eye from week 3 onwards. This was observed after orbital punction. No other clinical signs were noted in the males.
The only finding during the gestation period (gestation day 21) was a sparsely haired animal in the 250 mg/kg group. During the lactation period, sparsely haired animals were noted in the control (n = 1), 5 mg/kg (n = 1) and in the 250 mg/kg group (n = 1). No other findings were noted in the female animals.

BODY WEIGHT AND WEIGHT GAIN
Mean bodyweights of the treated male animals was comparable to the controls. The bodyweight change of the male animals of the high-dose group was significantly decreased from days 13-21. Mean bodyweights of the dams of the high-dose group was statistically significantly decreased on gestation day 21 and post-natal day 1. Mean bodyweight changes of the dams of the high-dose group were statistically significantly decreased from gestation day 14 to 21. Bodyweights and bodyweight change of the dams of all the treated groups were comparable to the controls group at all other times of the study.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Mean food consumption (g/kg/day) of male animals of the 250 mg/kg diet group was found to be statistically significantly decreased from day 7-13. No other treatment related effects were observed in the male animals.
During the gestation period and lactation period (gestation days 7-14 and 14-21 and post-natal days 1-4), food consumption (expressed as g/animal/day and g/kg bodyweight/day) of the dams in the high-dose group was significantly decreased. No other treatment-related effects were observed.
Test substance intake was as follows:
- Males (listed as low, mid and high dose groups; 5, 25 and 250 mg/kg diet respectively)
premating days 0-7: 0.4, 1.7 and 17.4 mg/kg bodyweight/day
premating days 7-13: 0.3, 1.6 and 15.4 mg/kg bodyweight/day
post-mating days 21-28: 0.3, 1.5 and 14.5 mg/kg bodyweight/day

- Females (listed as low, mid and high dose groups; 5, 25 and 250 mg/kg diet respectively)
premating days 0-7: 0.4, 1.7 and 17.4 mg/kg bodyweight/day
premating days 7-13: 0.3, 1.6 and 15.4 mg/kg bodyweight/day
gestation days 0-7: 0.4, 2.0 and 17.4 mg/kg bodyweight/day
gestation days 7-14: 0.4, 1.9 and 16.7 mg/kg bodyweight/day
gestation days 14-21: 0.3, 1.4 and 11.2 mg/kg bodyweight/day
Post-natal days 1-4: 0.5, 2.4 and 17.4 mg/kg bodyweight/day

HAEMATOLOGY
All treated groups were found to be comparable to controls

CLINICAL CHEMISTRY
Statistically significantly increased alkaline phosphatase levels (U/L) were found in the high-dose males. Bilirubin (µmol/L) was found to be statistically significantly increased in the high-dose females. These findings were considered to be treatment related. Other effects such as the statistically significant increase in chloride in the 25 mg/kg male rats and the significant decrease in calcium in the 5 mg/kg females were not considered to be related to treatment. No other changes were observed.

NEUROBEHAVIOUR
No treatment-related effects were observed.

ORGAN WEIGHTS
The absolute thymus weight in the males of the 250 and 25 mg/kg groups were found to be significantly decreased. Relative thymus weight was found to be significantly decreased in the high dose male rats.
The absolute and relative weight of the female animals of the high dose group was significantly decreased. In the mid-dose group the relative thymus weight was also statistically significantly decreased.
In the female animals of the high-dose group, the relative kidney and liver weights were statistically significantly decreased.
No other effects were observed in either male or female animals.

GROSS PATHOLOGY
At necropsy, a decrease in thymic size was seen in all animals in the 250 mg/kg diet groups, 11 females in the 25 mg/kg diet group, 7 females in the 5 mg/kg group and 5 animals in the control group.
Examination of the female that was found dead revealed hydrothorax, haemorrhagic lungs, dilation of the vena cava and haemorrhagic discharge in the vagina, these were considered to be indicative of problems during parturition.

HISTOPATHOLOGY
Microscopic evaluation of the thymus revealed moderate to very severe lymphoid depletion in all animals (both sexes) of the 250 mg/kg group and in all females of the 25 mg/kg group. Lymphoid depletion was characterised by a decrease in the thymic lobules due to an extensive loss of cortical and medullary small lymphocytes. The distinction between the cortical and medullary areas was unclear. In the more extreme effects observed, the cortex was very small, or absent. The remaining lymphoid cells visible in the cortical areas were mainly lymphoblasts. Lymphoblastic cells and reticuloepithelial cells had increased, and/or higher numbers of these cells were visible due to the disappearance of small lymphocytes and the collapse of the thymic stroma. In 3 high-dose females, lymphoid depletion was accompanied by lymphoid depletion in the PALS (periateriolar lymphocyte sheath areas) in the spleen. The macroscopically observed thymi in 5 control and 7 low dose females exhibited no microscopic abnormalities. In the thymi of the 2 control and 2 low dose females pregnancy/lactation involution was observed. The thymic lobules were decreased in size but exhibited normal structure with the histological appearance of age-involution. Increased glycomeric vacuolation, viz moderate versus very slight was seen in the liver of 4 high dose females and was considered to be a potential cause of the increased weight.
Examination of the reproductive organs revealed a statistically significant increased in the incidence of cysts in the ovaries of 8 high-dose females.

OTHER FINDINGS
In the reproductive and developmental screening observations of this study, increased duration of gestation, increased implantation loss, an increased number of still born pups and pup mortality at postnatal day 4, decreased pup weight at postnatal day and an increased number of runts and postnatal day 1 were all observed in the high dose group.

Dose descriptor:

NOAEL

Effect level:

0.3 - 0.4 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Decreased thymus weight

Dose descriptor:

NOAEL

Effect level:

0.3 - 0.5 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Decreased thymus weight and microscopic and macroscopic changes in the thymus

Dose descriptor:

NOAEL

Effect level:

5 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Reduced thymus weights (male and female animals), microscopic and macroscopic changes in the thymus (females only)

Critical effects observed:

not specified

Table 1: Test material concentration in experimental diets

Nominal concentration (mg/kg)	Mean Nominal Measured Concentration (mg/kg)	Percent of Nominal
0 (#1)	<0.05	NA
0 (#2)	<0.05	NA
0 (#3)	<0.05	NA
5 (#1)	4.52	90
5 (#2)	4.93	99
5 (#3)	4.40	88
25 (#1)	24.9	100
25 (#2)	26.5	106
25 (#3)	26.3	105
250 (#1)	247	99
250 (#2)	240	96
250 (#3)	244	98

#3: repeated analysis of batch no. 2

 

Table 2: Summary of relevant treatment related findings

Parameter	Dose levels
	5 mg/kg diet	25 mg/kg diet	250 mg/kg diet
Bodyweight: GD 21, PN 1 (females only)			Decreased
Bodyweight change: GD 14-21 (females only)			Decreased
Food consumption: PM 7-13 (males) GD 7-14, 14-21 and PN 1-4 (females only)			Decreased
Bilirubin (females only)			Increased
Alkaline phosphatase (males only)			Increased
Relative liver weight (females only)			Increased
Relative kidney weight (females only)			Increased
Absolute and/or relative thymus weight		Decreased	Decreased
Thymus: lymphoid depletion (males only)			Increased
Thymus: lymphoid depletion (females only)		Increased	Increased
Ovary: cysts (females only)			Increased
Liver: glycogenic vacuolation (females only)			Increased

Conclusions:

Based on the effects noted in the thymus in both male and female rats in the 25 mg/kg diet groups, the NOAEL was concluded to be the lowest group tested, 5 mg/kg diet which was equivalent to 0.3-0.4 mg/kg bw/day for male animals and 0.3-0.5 mg/kg bw/day for female animals.

Executive summary:

The repeated dose toxicity of the test substance was assessed in a repeated dose toxicity and reproductive and developmental screening study in rats. The study was performed in accordance with GLP and to the standardised guideline OECD 422. Only one death was noted during the study, and this was not attributed to toxicity of the test substance. Based on the effects noted in the thymus in both male and female rats in the 25 mg/kg diet groups, the NOAEL was concluded to be the lowest group tested, 5 mg/kg diet which was equivalent to 0.3-0.4 mg/kg bw/day for male animals and 0.3-0.5 mg/kg bw/day for female animals.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 443

Deviations:

yes

Remarks:

see free text

Principles of method if other than guideline:

additional endpoint: bone density (DEXA)

GLP compliance:

yes

Limit test:

no

Route of administration:

oral: feed

Vehicle:

other: in diet

Analytical verification of doses or concentrations:

yes

Dose / conc.:

0 mg/kg diet

Dose / conc.:

5 mg/kg diet

Dose / conc.:

25 mg/kg diet

Dose / conc.:

200 mg/kg diet

Control animals:

yes

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test article-related effects on body weight gain were observed for males and females
provided with 200 ppm.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Test article-related effects on food consumption were observed for females provided
with 200 ppm.

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Test article-related effects were noted in the white cells and red cell parameters
following 200 ppm exposure.
Neutrophil were marginally higher for males provided with 200 ppm, compared with
control, at the end of the in-life phase, although statistical significance was not
achieved. Females provided with 200 ppm also showed an increase in neutrophil
counts on LD 22, with statistical significance achieved for percentage neutrophils
(P < 0.05). Percentage leucocytes and monocytes was also increased for 200 ppm
females on LD 22, compared with controls (P < 0.05 and P < 0.01, respectively)
Mean cell volume and mean cell hemoglobin were significantly increased on LD 22
for females provided with 200 ppm), compared with control (P < 0.05 and P < 0.01
respectively). Increases in absolute reticulocyte counts and lower mean red cell
distribution width were also observed, compared with controls (P < 0.05).
No test article-related effect was noted following exposure of 5 or 25 ppm.

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

effects observed, treatment-related

Description (incidence and severity):

Small thymus was recorded for both sexes provided with 200 ppm, but was most
notable in females, which generally correlated with microscopic findings.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Test article-related changes in ovarian weights were recorded for females provided
with 200 ppm, and changes in thymic weights were recorded for both sexes provided
with 200 ppm, compared with concurrent controls.
Decreased absolute thymic weights and thymus:body weight ratios were recorded for
females provided with 25 ppm and both sexes provided with 200 ppm, compared with
concurrent controls, which correlated with macroscopic and microscopic findings.
A minor decrease in absolute ovarian weights and ovary:body weight ratios were
recorded for females provided with 200 ppm, compared with concurrent controls

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Small thymus was recorded for both sexes provided with 200 ppm, but was most
notable in females, which generally correlated with microscopic findings.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Description (incidence and severity):

No test article-related alterations in bone area, bone mineral content, and bone mineral
density were noted in F0 generation animals.

Key result

Dose descriptor:

NOAEL

Effect level:

25 mg/kg diet

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

gross pathology

organ weights and organ / body weight ratios

Key result

Dose descriptor:

NOAEL

Effect level:

5 mg/kg diet

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

Key result

Dose descriptor:

NOAEL

Effect level:

200 mg/kg diet

Based on:

test mat.

Sex:

female

Basis for effect level:

gross pathology

organ weights and organ / body weight ratios

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

200 mg/kg diet

System:

immune system

Organ:

thymus

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

no

Conclusions:

Oral (dietary) administration of control article (vehicle) or 5, 25 or 200 ppm
(equivalent to a nominal dose level of 0, 0.4, 1.8, or 11.8 mg/kg/day) Dioctyltin Oxide
to Han Wistar rats for up to two consecutive generations resulted in test article-related
effects at all dose levels.
Systemic effects in the F0 generation included changes in thymus following
administration of 200 ppm for both sexes and following administration of 25 ppm to
females. The kidney changes noted for F0 females were considered not adverse;
therefore, a no observed adverse effect level (NOAEL) was established as 25 ppm for
systemic toxicity for males and 5 ppm for females for the F0 generation.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

0.3 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The single study presented under this endpoint was performed and reported to a high standard and as such was assigned a reliability score of 1 in accordance with the criteria for assessing data quality as described in Klimisch (1997).

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

ORAL

The key study, Waalkens-Berendsen (2004), a repeated dose toxicity and reproductive and developmental screening study in rats was performed in accordance with GLP and to the standardised guideline OECD 422. The study was performed to a high standard and the reporting was to a sufficient level to assess the quality of the data presented. The study was therefore awarded a reliability score of 1 in accordance with the criteria for assessing data quality as defined in Klimisch (1997). It was therefore considered justified to base conclusions of the toxicological nature of the substance on the findings of this study. Based on the effects noted in the thymus in both male and female rats in the 25 mg/kg diet groups, the NOAEL was concluded to be the lowest group tested, 5 mg/kg diet which was equivalent to 0.3-0.4 mg/kg bw/day for male animals and 0.3-0.5 mg/kg bw/day for female animals.

INHALATION

An adaptation to the standard data requirements has been provided to fulfil this data requirement, as it is not considered to be the most appropriate route of exposure, and since a more appropriate study is available, testing for this endpoint was omitted.

DERMAL

An adaptation to the standard data requirements has been provided to fulfil this data requirement, as it is not considered to be the most appropriate route of exposure, and since a more appropriate study is available, testing for this endpoint was omitted.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
One study was available for evaluation of the repeated dose toxicity of the substance. The study was performed to a standardised guideline, in line with GLP and reported to a high standard sufficient to assess the quality of the presented data. As it was possible to derive an appropriate effect level that may be used with appropriate assessment factors in a risk assessment, the study was considered suitable for use as the key study.

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: thymus

Justification for classification or non-classification

Several studies in the structure surogate Dioctyltin dichloride shw, that Dioctyltin dichloride causes an adverse in the immune system after a single exposure. Under consideration of the different bioavailability (DOTC >> DOTO) and from human data (EMA, FDA) it is considered that is appropriated to classify Dioctyltin oxide in accordance with the Regulation (EC) No. 1272/2008 and Directive 67/548/EEC, based on the observations in the thymus, the substance is classified as STOT Single. Exp. 2: H371: