Dioctyltin oxide

Toxicity to reproduction

Administrative data

Endpoint:

extended one-generation reproductive toxicity - with developmental neurotoxicity (Cohorts 1A, 1B without extension, 2A and 2B)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study Initiation Date: 04 June 2018, Experimental Completion Date: 24 June 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Pursuant to Articles 10(a)(vi) and/or (vii), 12(1)(d) and 13(4) of the REACH Regulation, a
technical dossier registered at 100 to 1000 tonnes per year shall contain as a minimum the
information specified in Annexes VII to IX of the REACH Regulation.
The basic test design of an extended one-generation reproductive toxicity study (Cohorts 1A
and 1B, without extension of Cohort 1B to include a F2 generation, and without Cohorts 2A,
2B and 3) is a standard information requirement as laid down in column 1 of 8.7.3., Annex
IX of the REACH Regulation if the available repeated dose toxicity studies (e.g. 28-day or
90-day studies, OECD TGs 421 or 422 screening studies) indicate adverse effects on
reproductive organs or tissues or reveal other concerns in relation with reproductive
toxicity. If the conditions described in column 2 of Annex IX are met, the study design
needs to be expanded to include the extension of Cohort 1B, Cohorts 2A/2B, and/or Cohort
3. Adequate information on this endpoint needs to be present in the technical dossier for the
registered substance to meet this information requirement.
a) The information requirement
You have sought to adapt this information requirement according to Section 3 of Annex XI
of the REACH Regulation using the same justification as for the adaptation proposed for the
prenatal developmental toxicity study (Section 2). However, ECHA notes similarly to Section
2, for the prenatal developmental toxicity, that none of the criteria of that adaptation
(3.2(a); 3.2(b); or 3.2(c)) are currently fulfilled.
Therefore, ECHA considers that this adaptation of the information requirement does not
meet the requirements set forth under Section 3 of Annex XI.
ECHA considers that adverse effects on reproductive organs or tissues and other concerns in
relation with reproductive toxicity are observed. More specifically, you provided a screening
study in rats (Waalkens-Berendsen, 2004) performed with the registered substance
according to OECD TG 422. In this study reproductive effects such as increased duration of
gestation, increased implantation loss, an increased number of still born pups and pup
mortality at postnatal day 4, decreased pup weight and an increased number of runts at
postnatal day 1, and a statistically significant increase in the incidence of cysts in the
ovaries of 8 high-dose females were seen, albeit in the high-dose only, in the presence of
maternal toxicity (severe effects in thymus).
Pursuant to Annex IX, Section 8.7.3. an extended one-generation reproductive toxicity
study is thus an information requirement for registration of the registered substance.
ECHA further notes that this OECD 422 study does not provide the information required by
Annex IX, Section 8.7.3., because it does not cover key parameters, exposure duration, life
stages and statistical power of an extended one-generation reproductive toxicity study. The
main missing key aspects/elements are: At least 20 pregnant females per group, an
extensive post-natal evaluation of the F1 generation, and investigation of (developmental)
immunotoxicity.
ECHA concludes that the information available on this endpoint for the registered substance
in the technical dossier does not meet the information requirement. Consequently there is
an information gap and it is necessary to provide information for this endpoint. Thus, an
extended one-generation reproductive toxicity study according to columns 1 and 2 of 8.7.3.,
Annex IX is required. The following refers to the specifications of this required study.
b) The specifications for the required study
Premating exposure duration and dose-level setting
To ensure that the study design adequately addresses the fertility endpoint, the duration of
the premating exposure period and the selection of the highest dose level are key aspects
to be considered. According to ECHA Guidance, the starting point for deciding on the length
of premating exposure period should be ten weeks to cover the full spermatogenesis and
folliculogenesis before the mating, allowing meaningful assessment of the effects on
fertility.
Ten weeks premating exposure duration is required because there is no substance specific
information in the dossier supporting shorter premating exposure duration as advised in the
ECHA Guidance on information requirements and chemical safety assessment R.7a, chapter
R.7.6 (version 4.0, July 2015). The exposure duration is supported also by the lipophilicity
of the substance to ensure that the steady state in parental animals has been reached
before mating.
The highest dose level shall aim to induce some toxicity to allow comparison of effect levels
and effects of reproductive toxicity with those of systemic toxicity. The dose level selection
should be based upon the fertility effects with the other cohorts being tested at the same
dose levels.
It is recommended that results from a range-finding study (or range finding studies) for the
extended one-generation reproductive toxicity study are reported with the main study. This
will support the justifications of the dose level selections and interpretation of the results.
Extension of Cohort 1B
If the column 2 conditions of 8.7.3., Annex IX are met, Cohort 1B must be extended, which
means that the F2 generation is produced by mating the Cohort 1B animals. This extension
provides information also on the sexual function and fertility of the F1 animals.
The use of the registered substance is leading to significant exposure of workers and
consumers because the registered substance has industrial and consumer uses such as in
adhesive, sealants, coatings and paints, thinners, paint removes, textile dyes. Furthermore,
effects indicating endocrine disrupting mode of action such as increase in gestation length
were observed in the OECD TG 422 study (see above). Furthermore, the estimated LogKow
of 9.26 of the registered substance indicates a bioaccumulative potential.
Therefore, ECHA concludes that Cohort 1B must be extended to include mating of the
animals and production of the F2 generation because the uses of the registered substance is
leading to significant exposure of industrial workers and consumers and the internal dose
for the registered substance and or any of its metabolites is estimated to reach a steady
state in the test animals only after an extended exposure based on the high estimated
LogKow of the registered substance and the OECD TG 422 study indicates modes of action
related to endocrine disruption for the registered substance.
Cohort 3
The developmental immunotoxicity Cohort 3 needs to be conducted in case of a particular
concern on (developmental) immunotoxicity as described in column 2 of 8.7.3., Annex IX.
ECHA notes that existing information provided in the dossier on the registered substance in
the OECD TG 422 study shows evidence of immunotoxicity and severe thymus toxicity
(thymus atrophy).
Upon receipt of the draft decision you submitted comments explaining that:
“The registrant agrees to get information concerning reproduction toxicity, on strength of
information lack in a further generation.
However, there exists an OECD 443 (IUCLID section 7.8.3) study on the structural analogue
surrogate Dioctyltin dichloride. This study was not considered as relevant for Dioctyltin
dichloride because of the different gastric metabolism and the different bioavailability of the
substances (chloride vs. oxide) and the fact that the study did not integrate the acute
immune effects in parent and juvenile animals. In subacute, subchronic and development /
reproduction toxicity studies, it is important that for an acute immune suppressive
substance the acute immunotoxicity is considered as a relevant endpoint.
Based on these considerations the lead registrant proposes a tiered approach based on the
outcome of extended OECD 414 (section 2) in progress.
The following justification should be considered:
- Acute immune toxicity is not determined in OECD TG 443, only immune
toxicity, therefore a misinterpretation as repeated exposure toxicity possible.
- If acute immune toxicity is not determined, acute immune toxicity in juvenile
animals may lead to an interpretation as developmental immune toxicity.
- Determination if immune toxicity caused by Dioctyltin oxide follows Habers
Rule.
- If OECD 414 shows a positive teratogenic outcome, performance of OECD 443
may not be appropriate considering animal welfare.
The lead registrant is aware of his responsibility regarding human, environment and nature;
in addition the German “Grundgesetz” includes the fundamental right of animal welfare.
Thus we want to avoid any inappropriate animal experiment without value for human and
environment. Therefore, the proposed tiered approach under consideration of the outcome
of the extended OECD 414 is supports the weight of legally protected rights.”
ECHA acknowledges your comments and the proposed tiered approach for performing the
OECD TG 443. However, ECHA notes that unless the outcome of the ongoing OECD 414 is a
classification of the substance as Reproductive toxicity Category 1A or 1B (H360F) and the
available data are adequate to support a robust risk assessment, the PNDT study cannot be
used to waive the EORGTS study. Information from the pre-natal developmental toxicity
study (OECD TG 414) regarding sexual function and fertility is limited to the maintenance of
the pregnancy from implantation up to close to the parturition. It does not provide
information on hazardous properties to the postnatal development including sexual
maturation and histopathological integrity of the reproductive organs at adulthood. Thus,
the information from these studies cannot fulfill the data requirement for this endpoint.
This information does not allow either to assume/conclude that the substance has not
hazardous properties with regard to sexual function and fertility, would you want to use this
study in the context of adaptation possibilities offered by Annex XI. Consequently the draft
decision was not amended.
ECHA concludes that the developmental immunotoxicity cohort 3 needs to be conducted
because there is a particular concern on (developmental) immunotoxicity based on the
results from the above-identified in vivo study on the registered substance.
The study design must be justified in the dossier and, thus, the existence/non-existence of
the conditions/triggers must be documented.
Species and route selection
According to the test method EU B.56/ OECD TG 443, the rat is the preferred species. On
the basis of this default consideration, ECHA considers that testing should be performed in
rats.
ECHA considers that the oral route is the most appropriate route of administration for
substances except gases to focus on the detection of hazardous properties on reproduction
as indicated in ECHA Guidance on information requirements and chemical safety assessment
(version 4.0, July 2015) R.7a, chapter R.7.6.2.3.2. Since the substance to be tested is a
solid, ECHA concludes that testing should be performed by the oral route.
Outcome
Therefore, pursuant to Article 41(1) and (3) of the REACH Regulation, you are requested to
submit the following information derived with the registered substance subject to the
present decision: Extended one-generation reproductive toxicity study (test method EU
B.56/ OECD TG 443), in rats, oral route, according to the following study-design
specifications:
o Ten weeks premating exposure duration for the parental (P0) generation;
o Dose level setting shall aim to induce some toxicity at the highest dose level;
o Cohort 1A (Reproductive toxicity);
o Cohort 1B (Reproductive toxicity) with extension to mate the Cohort 1B
animals to produce the F2 generation; and
o Cohort 3 (Developmental immunotoxicity).
Notes for your consideration
No triggers for the inclusion of Cohorts 2A and 2B (developmental neurotoxicity) were
identified. However, you may expand the study by including Cohorts 2A and 2B if new
information becomes available after this decision is issued to justify such an inclusion.
Inclusion is justified if the new information shows triggers which are described in column 2
of Section 8.7.3., Annex IX and further elaborated in ECHA Guidance on information
requirements and chemical safety assessment R.7a, chapter R.7.6 (version 4.0, July 2015).
You may also expand the study to address a concern identified during the conduct of the
extended one-generation reproduction toxicity study and also due to other scientific reasons
in order to avoid a conduct of a new study. The justification for the expansion must be
documented. The study design must be justified in the dossier and, thus, the existence/nonexistence
of the conditions/triggers must be documented.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 443 (Extended One-Generation Reproductive Toxicity Study)

Deviations:

yes

Remarks:

see free text

Principles of method if other than guideline:

additional endpoints: Sn in plasma, Sn in milk, bone density

GLP compliance:

yes

Limit test:

no

Justification for study design:

Pursuant to Articles 10(a)(vi) and/or (vii), 12(1)(d) and 13(4) of the REACH Regulation, a
technical dossier registered at 100 to 1000 tonnes per year shall contain as a minimum the
information specified in Annexes VII to IX of the REACH Regulation.
The basic test design of an extended one-generation reproductive toxicity study (Cohorts 1A
and 1B, without extension of Cohort 1B to include a F2 generation, and without Cohorts 2A,
2B and 3) is a standard information requirement as laid down in column 1 of 8.7.3., Annex
IX of the REACH Regulation if the available repeated dose toxicity studies (e.g. 28-day or
90-day studies, OECD TGs 421 or 422 screening studies) indicate adverse effects on
reproductive organs or tissues or reveal other concerns in relation with reproductive
toxicity. If the conditions described in column 2 of Annex IX are met, the study design
needs to be expanded to include the extension of Cohort 1B, Cohorts 2A/2B, and/or Cohort
3. Adequate information on this endpoint needs to be present in the technical dossier for the
registered substance to meet this information requirement.
a) The information requirement
You have sought to adapt this information requirement according to Section 3 of Annex XI
of the REACH Regulation using the same justification as for the adaptation proposed for the
prenatal developmental toxicity study (Section 2). However, ECHA notes similarly to Section
2, for the prenatal developmental toxicity, that none of the criteria of that adaptation
(3.2(a); 3.2(b); or 3.2(c)) are currently fulfilled.
Therefore, ECHA considers that this adaptation of the information requirement does not
meet the requirements set forth under Section 3 of Annex XI.
ECHA considers that adverse effects on reproductive organs or tissues and other concerns in
relation with reproductive toxicity are observed. More specifically, you provided a screening
study in rats (Waalkens-Berendsen, 2004) performed with the registered substance
according to OECD TG 422. In this study reproductive effects such as increased duration of
gestation, increased implantation loss, an increased number of still born pups and pup
mortality at postnatal day 4, decreased pup weight and an increased number of runts at
postnatal day 1, and a statistically significant increase in the incidence of cysts in the
ovaries of 8 high-dose females were seen, albeit in the high-dose only, in the presence of
maternal toxicity (severe effects in thymus).
Pursuant to Annex IX, Section 8.7.3. an extended one-generation reproductive toxicity
study is thus an information requirement for registration of the registered substance.
ECHA further notes that this OECD 422 study does not provide the information required by
Annex IX, Section 8.7.3., because it does not cover key parameters, exposure duration, life
stages and statistical power of an extended one-generation reproductive toxicity study. The
main missing key aspects/elements are: At least 20 pregnant females per group, an
extensive post-natal evaluation of the F1 generation, and investigation of (developmental)
immunotoxicity.
ECHA concludes that the information available on this endpoint for the registered substance
in the technical dossier does not meet the information requirement. Consequently there is
an information gap and it is necessary to provide information for this endpoint. Thus, an
extended one-generation reproductive toxicity study according to columns 1 and 2 of 8.7.3.,
Annex IX is required. The following refers to the specifications of this required study.
b) The specifications for the required study
Premating exposure duration and dose-level setting
To ensure that the study design adequately addresses the fertility endpoint, the duration of
the premating exposure period and the selection of the highest dose level are key aspects
to be considered. According to ECHA Guidance, the starting point for deciding on the length
of premating exposure period should be ten weeks to cover the full spermatogenesis and
folliculogenesis before the mating, allowing meaningful assessment of the effects on
fertility.
Ten weeks premating exposure duration is required because there is no substance specific
information in the dossier supporting shorter premating exposure duration as advised in the
ECHA Guidance on information requirements and chemical safety assessment R.7a, chapter
R.7.6 (version 4.0, July 2015). The exposure duration is supported also by the lipophilicity
of the substance to ensure that the steady state in parental animals has been reached
before mating.
The highest dose level shall aim to induce some toxicity to allow comparison of effect levels
and effects of reproductive toxicity with those of systemic toxicity. The dose level selection
should be based upon the fertility effects with the other cohorts being tested at the same
dose levels.
It is recommended that results from a range-finding study (or range finding studies) for the
extended one-generation reproductive toxicity study are reported with the main study. This
will support the justifications of the dose level selections and interpretation of the results.
Extension of Cohort 1B
If the column 2 conditions of 8.7.3., Annex IX are met, Cohort 1B must be extended, which
means that the F2 generation is produced by mating the Cohort 1B animals. This extension
provides information also on the sexual function and fertility of the F1 animals.
The use of the registered substance is leading to significant exposure of workers and
consumers because the registered substance has industrial and consumer uses such as in
adhesive, sealants, coatings and paints, thinners, paint removes, textile dyes. Furthermore,
effects indicating endocrine disrupting mode of action such as increase in gestation length
were observed in the OECD TG 422 study (see above). Furthermore, the estimated LogKow
of 9.26 of the registered substance indicates a bioaccumulative potential.
Therefore, ECHA concludes that Cohort 1B must be extended to include mating of the
animals and production of the F2 generation because the uses of the registered substance is
leading to significant exposure of industrial workers and consumers and the internal dose
for the registered substance and or any of its metabolites is estimated to reach a steady
state in the test animals only after an extended exposure based on the high estimated
LogKow of the registered substance and the OECD TG 422 study indicates modes of action
related to endocrine disruption for the registered substance.
Cohort 3
The developmental immunotoxicity Cohort 3 needs to be conducted in case of a particular
concern on (developmental) immunotoxicity as described in column 2 of 8.7.3., Annex IX.
ECHA notes that existing information provided in the dossier on the registered substance in
the OECD TG 422 study shows evidence of immunotoxicity and severe thymus toxicity
(thymus atrophy).
Upon receipt of the draft decision you submitted comments explaining that:
“The registrant agrees to get information concerning reproduction toxicity, on strength of
information lack in a further generation.
However, there exists an OECD 443 (IUCLID section 7.8.3) study on the structural analogue
surrogate Dioctyltin dichloride. This study was not considered as relevant for Dioctyltin
dichloride because of the different gastric metabolism and the different bioavailability of the
substances (chloride vs. oxide) and the fact that the study did not integrate the acute
immune effects in parent and juvenile animals. In subacute, subchronic and development /
reproduction toxicity studies, it is important that for an acute immune suppressive
substance the acute immunotoxicity is considered as a relevant endpoint.
Based on these considerations the lead registrant proposes a tiered approach based on the
outcome of extended OECD 414 (section 2) in progress.
The following justification should be considered:
- Acute immune toxicity is not determined in OECD TG 443, only immune
toxicity, therefore a misinterpretation as repeated exposure toxicity possible.
- If acute immune toxicity is not determined, acute immune toxicity in juvenile
animals may lead to an interpretation as developmental immune toxicity.
- Determination if immune toxicity caused by Dioctyltin oxide follows Habers
Rule.
- If OECD 414 shows a positive teratogenic outcome, performance of OECD 443
may not be appropriate considering animal welfare.
The lead registrant is aware of his responsibility regarding human, environment and nature;
in addition the German “Grundgesetz” includes the fundamental right of animal welfare.
Thus we want to avoid any inappropriate animal experiment without value for human and
environment. Therefore, the proposed tiered approach under consideration of the outcome
of the extended OECD 414 is supports the weight of legally protected rights.”
ECHA acknowledges your comments and the proposed tiered approach for performing the
OECD TG 443. However, ECHA notes that unless the outcome of the ongoing OECD 414 is a
classification of the substance as Reproductive toxicity Category 1A or 1B (H360F) and the
available data are adequate to support a robust risk assessment, the PNDT study cannot be
used to waive the EORGTS study. Information from the pre-natal developmental toxicity
study (OECD TG 414) regarding sexual function and fertility is limited to the maintenance of
the pregnancy from implantation up to close to the parturition. It does not provide
information on hazardous properties to the postnatal development including sexual
maturation and histopathological integrity of the reproductive organs at adulthood. Thus,
the information from these studies cannot fulfill the data requirement for this endpoint.
This information does not allow either to assume/conclude that the substance has not
hazardous properties with regard to sexual function and fertility, would you want to use this
study in the context of adaptation possibilities offered by Annex XI. Consequently the draft
decision was not amended.
ECHA concludes that the developmental immunotoxicity cohort 3 needs to be conducted
because there is a particular concern on (developmental) immunotoxicity based on the
results from the above-identified in vivo study on the registered substance.
The study design must be justified in the dossier and, thus, the existence/non-existence of
the conditions/triggers must be documented.
Species and route selection
According to the test method EU B.56/ OECD TG 443, the rat is the preferred species. On
the basis of this default consideration, ECHA considers that testing should be performed in
rats.
ECHA considers that the oral route is the most appropriate route of administration for
substances except gases to focus on the detection of hazardous properties on reproduction
as indicated in ECHA Guidance on information requirements and chemical safety assessment
(version 4.0, July 2015) R.7a, chapter R.7.6.2.3.2. Since the substance to be tested is a
solid, ECHA concludes that testing should be performed by the oral route.
Outcome
Therefore, pursuant to Article 41(1) and (3) of the REACH Regulation, you are requested to
submit the following information derived with the registered substance subject to the
present decision: Extended one-generation reproductive toxicity study (test method EU
B.56/ OECD TG 443), in rats, oral route, according to the following study-design
specifications:
o Ten weeks premating exposure duration for the parental (P0) generation;
o Dose level setting shall aim to induce some toxicity at the highest dose level;
o Cohort 1A (Reproductive toxicity);
o Cohort 1B (Reproductive toxicity) with extension to mate the Cohort 1B
animals to produce the F2 generation; and
o Cohort 3 (Developmental immunotoxicity).
Notes for your consideration
No triggers for the inclusion of Cohorts 2A and 2B (developmental neurotoxicity) were
identified. However, you may expand the study by including Cohorts 2A and 2B if new
information becomes available after this decision is issued to justify such an inclusion.
Inclusion is justified if the new information shows triggers which are described in column 2
of Section 8.7.3., Annex IX and further elaborated in ECHA Guidance on information
requirements and chemical safety assessment R.7a, chapter R.7.6 (version 4.0, July 2015).
You may also expand the study to address a concern identified during the conduct of the
extended one-generation reproduction toxicity study and also due to other scientific reasons
in order to avoid a conduct of a new study. The justification for the expansion must be
documented. The study design must be justified in the dossier and, thus, the existence/nonexistence
of the conditions/triggers must be documented.

Test material

Test material information

Constituent 1

Reference substance name:

Dioctyltin oxide

EC Number:

212-791-1

EC Name:

Dioctyltin oxide

Cas Number:

870-08-6

Molecular formula:

C16H34OSn

IUPAC Name:

dioctylstannanone

Test material form:

solid

Remarks:

white powder

Details on test material:

- Name of test material : Di-n-octyltin oxide
- Molecular formula: C16H34OSn
- Molecular weight: 361.16
- Smiles notation: O=[Sn](CCCCCCCC)CCCCCCCC

Test animals

Species:

rat

Strain:

other: Crl:WI(Han)

Sex:

male/female

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: in rodent diet

Analytical verification of doses or concentrations:

yes

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg diet

Doses / concentrations 2

Dose / conc.:

5 mg/kg diet

Doses / concentrations 3

Dose / conc.:

25 mg/kg diet

Doses / concentrations 4

Dose / conc.:

200 mg/kg diet

Control animals:

yes, plain diet

Examinations

Oestrous cyclicity (parental animals):

No test article-related changes were noted

Sperm parameters (parental animals):

No test article-related changes were noted

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Description (incidence and severity):

No test article-related clinical observations were noted.

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):

Hematology assessments showed marginally higher neutrophil levels for males and
females provided with 200 ppm, compared with control, at the end of the in-life
phase. Percentage leucocytes and monocytes were also increased on LD 22 for
females provided with 200 ppm, compared with controls. Mean cell volume, mean
cell hemoglobin, and reticulocytes were increased on LD 22 for females provided
with 200 ppm, and lower mean red cell distribution width was observed.

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Immunological findings:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Description (incidence and severity):

a) Bones
No test article-related effect on femur length or bone area, bone mineral content, and
bone mineral density was observed following exposure at all dose levels, compared
with controls

b) Milk
Milk samples obtained from lactating females from all groups, including controls,
showed tin levels to be lower than the lower limit of quantitation (LLOQ).

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

no effects observed

Details on results (P0)

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.

Effect levels (P0)

1

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

organ weights and organ / body weight ratios

2

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

organ weights and organ / body weight ratios

Target system / organ toxicity (P0)

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

Results: P1 (second parental generation)

General toxicity (P1)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Test article-related clinical observations were noted for animals provided with
200 ppm, and consisted of isolated instances of high stepping gait noted for one male
during the weekly detailed observations. For females during gestation and lactation,
tail elevation was recorded for two females

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

For 200 ppm males, lower mean body weights and reduced food consumption were
observed from the initiation of the F1 phase, and remained lower until the end of the
phase, with an initial reduction in body weight gain observed during the first week of
the F1 phase compared with controls.
Lower mean body weight and food consumption were also observed during the
first five weeks of the F1 phase for females maternally exposed and provided with
200 ppm, compared with controls. Lower mean body weight gain was also noted
during the first week. Mean body weights were similar to controls during early and
mid-gestation. However, by GD 20, marginally lower mean body weights and body
weight gains were observed, with values still marginally lower during the
first four days of the lactation phase, with a corresponding reduction in food
consumption, compared with controls.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

For 200 ppm males, lower mean body weights and reduced food consumption were
observed from the initiation of the F1 phase, and remained lower until the end of the
phase, with an initial reduction in body weight gain observed during the first week of
the F1 phase compared with controls.
Lower mean body weight and food consumption were also observed during the
first five weeks of the F1 phase for females maternally exposed and provided with
200 ppm, compared with controls. Lower mean body weight gain was also noted
during the first week. Mean body weights were similar to controls during early and
mid-gestation. However, by GD 20, marginally lower mean body weights and body
weight gains were observed, with values still marginally lower during the
first four days of the lactation phase, with a corresponding reduction in food
consumption, compared with controls.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Males maternally exposed and provided with 200 ppm showed a reduction in
hemoglobin levels and corresponding increases in reticulocytes (counts and %),
compared with controls

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Males and females maternally exposed and provided with 200 ppm showed an
increase in alanine aminotransferase activity, compared with controls. Elevated mean
cholesterol levels, with a reduction in albumin levels, were also observed for males,
compared with controls.
Females maternally exposed and provided with 200 ppm also showed a reduction in
total protein and an increase in blood urea, compared with controls.

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

no effects observed

Description (incidence and severity):

No notable immunotoxicology findings for immunophenotyping and T-Cell
Dependent Antibody Response assessments were noted.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Lower mean thymus weights (absolute, and relative to body weight and brain weight)
were recorded for animals provided with 200 ppm, compared with controls. Although
no macroscopic findings were noted in the thymus, increased thymic atrophy was
recorded for animals maternally exposed and provided with 200 ppm, compared with
controls.
Increased liver weight ratios were recorded for males and increased heart weight
ratios were recorded for both sexes maternally exposed and provided with 200 ppm,
although no macroscopic or microscopic correlates were observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Reproductive function / performance (P1)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

The percentage post-implantation losses were twice as much in the 200 ppm group,
compared with controls. Litter size was also lower in this group on PND 1, although
sex ratio was unaffected.
Four F2 pups were recorded as missing (presumed cannibalized) and one dead pup
was recorded in the 200 ppm litters, compared to no dead/missing pups in control
litters. This was considered test article-related, which resulted in the lower PND 4
viability index for this group, and a smaller litter size on PND 4.
Test article-related clinical observations were noted for the 200 ppm litters. Blackened
/ dead tissue on the tail apex was recorded for three pups from two separate 200 ppm
litters. Red and thin appearance was also noted for four pups from one litter. These
observations were not observed for control litters. No further test article-related
clinical observations were noted in the 200 ppm F2 pups. No test article-related
clinical observations were noted in the 5 or 25 ppm F2 generation pups.
Marginally lower mean body weights (adjusted for litter size) were observed for
males and females from 200 ppm litters; these were considered not to have
represented an adverse effect on body weight.

Effect levels (P1)

1

Key result

Dose descriptor:

NOAEL

Effect level:

25 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

haematology

clinical biochemistry

organ weights and organ / body weight ratios

2

Key result

Dose descriptor:

LOAEL

Effect level:

200 mg/kg diet

Based on:

test mat.

Sex:

female

Basis for effect level:

other: post-implamentation lost, litter size

Target system / organ toxicity (P1)

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

200 mg/kg diet

System:

immune system

Organ:

blood

thymus

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

no

Results: F1 generation

General toxicity (F1)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Test article-related clinical observations were noted for animals provided with
200 ppm, and consisted of isolated instances of high stepping gait noted for one male
during the weekly detailed observations. For females during gestation and lactation,
tail elevation was recorded for two females.

Mortality / viability:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

For 200 ppm males, lower mean body weights and reduced food consumption were
observed from the initiation of the F1 phase, and remained lower until the end of the
phase, with an initial reduction in body weight gain observed during the first week of
the F1 phase compared with controls.
Lower mean body weight and food consumption were also observed during the
first five weeks of the F1 phase for females maternally exposed and provided with
200 ppm, compared with controls. Lower mean body weight gain was also noted
during the first week. Mean body weights were similar to controls during early and
mid-gestation. However, by GD 20, marginally lower mean body weights and body
weight gains were observed, with values still marginally lower during the
first four days of the lactation phase, with a corresponding reduction in food
consumption, compared with controls.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

For 200 ppm males, lower mean body weights and reduced food consumption were
observed from the initiation of the F1 phase, and remained lower until the end of the
phase, with an initial reduction in body weight gain observed during the first week of
the F1 phase compared with controls.
Lower mean body weight and food consumption were also observed during the
first five weeks of the F1 phase for females maternally exposed and provided with
200 ppm, compared with controls. Lower mean body weight gain was also noted
during the first week. Mean body weights were similar to controls during early and
mid-gestation. However, by GD 20, marginally lower mean body weights and body
weight gains were observed, with values still marginally lower during the
first four days of the lactation phase, with a corresponding reduction in food
consumption, compared with controls.

Food efficiency:

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Males maternally exposed and provided with 200 ppm showed a reduction in
hemoglobin levels and corresponding increases in reticulocytes (counts and %),
compared with controls.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Males and females maternally exposed and provided with 200 ppm showed an
increase in alanine aminotransferase activity, compared with controls. Elevated mean
cholesterol levels, with a reduction in albumin levels, were also observed for males,
compared with controls.
Females maternally exposed and provided with 200 ppm also showed a reduction in
total protein and an increase in blood urea, compared with controls.

Urinalysis findings:

not examined

Sexual maturation:

effects observed, treatment-related

Description (incidence and severity):

Sexual maturity was delayed for males and females maternally and directly exposed
to 200 ppm, compared with controls. This is a secundary effect based on lower food
consumtion and delayed body weight increase

Anogenital distance (AGD):

no effects observed

Nipple retention in male pups:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Lower mean thymus weights (absolute, and relative to body weight and brain weight)
were recorded for animals provided with 200 ppm, compared with controls. Although
no macroscopic findings were noted in the thymus, increased thymic atrophy was
recorded for animals maternally exposed and provided with 200 ppm, compared with
controls.
Increased liver weight ratios were recorded for males and increased heart weight
ratios were recorded for both sexes maternally exposed and provided with 200 ppm,
although no macroscopic or microscopic correlates were observed

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Lower mean thymus weights (absolute, and relative to body weight and brain weight)
were recorded for animals provided with 200 ppm, compared with controls. Although
no macroscopic findings were noted in the thymus, increased thymic atrophy was
recorded for animals maternally exposed and provided with 200 ppm, compared with
controls.
Increased liver weight ratios were recorded for males and increased heart weight
ratios were recorded for both sexes maternally exposed and provided with 200 ppm,
although no macroscopic or microscopic correlates were observed

Histopathological findings:

effects observed, treatment-related

Description (incidence and severity):

Increased liver weight ratios were recorded for males and increased heart weight
ratios were recorded for both sexes maternally exposed and provided with 200 ppm,
although no macroscopic or microscopic correlates were observed

Developmental neurotoxicity (F1)

Behaviour (functional findings):

not examined

Developmental immunotoxicity (F1)

Developmental immunotoxicity:

no effects observed

Effect levels (F1)

1

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

200 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

developmental immunotoxicity

2

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

25 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Overall reproductive toxicity

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

200 mg/kg diet

Treatment related:

yes

Relation to other toxic effects:

reproductive effects as a secondary non-specific consequence of other toxic effects

Dose response relationship:

yes

Relevant for humans:

no

Applicant's summary and conclusion

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.
Marginally lower mating and fertility indices were noted in the F1 generation
following administration of 200 ppm, however, this was considered nonadverse,
therefore the no observed effect level (NOEL) for reproductive toxicity is 200 ppm.
Immunotoxicity effects in the F1 generation consisted of a reduction of TDAR
coupled with slight reductions in circulating blood T lymphocyte numbers at all dose
levels, compared with controls, with the effect more prominent for males. In the
absence of any associated changes in hematology parameters, these findings were
considered nonadverse. As such, the NOAEL is 200 ppm for developmental
immunotoxicity.
Based on lower body weights, delayed sexual maturation which resulted as a
secondary effect to the lower mean body weights, in the F1 generation, and smaller
litter sizes and pup mortality in the F2 generation following administration of
200 ppm, the NOEL for offspring growth and development is established as 25 ppm.
No evidence of any endocrine disturbance was noted in this study.