Tin bis(2-ethylhexanoate)

Endpoint summary

Description of key information

Subchronic repeated-dose (90 day) studies are available for the two hydrolysis products of tin bis(2 -ethylhexanoate), stannous chloride and ethylhexanoic acid. These studies report a decrease in body weight gain at higher doses for both materials and mild effects on liver and kidney weights and liver histopathology for EHA only. The liver effects for EHA were considered to be adaptive in nature and not toxic effects. The NOAELs for both materials were nearly the same, 300 mg/kg/d.

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:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Read Across to an analogue based on structural similarity. An analogue justification is attached to section 13 of the dataset.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Clinical signs:

no effects observed

Description (incidence and severity):

No significant clinical signs of toxicity occurred during the rat study.

Mortality:

no mortality observed

Description (incidence):

No mortality occurred during the rat study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

In rats, body weight gain was slightly lower for animals consuming diets containing 1.5% EHA compared with the control groups. Mean body weights for the 1.5% male and female rat groups were respectively 8% and 10% lower (P<=0.05) at the end of the treatment period and were statistically (P<=0.05) lower than the control group beginning after the first week on test. Mean body weights of rats consuming diets containing 0.5% or 0.1% EHA were unaffected compared with controls. During the recovery phase, body weight gain for animals that had received 1.5% EHA increased so that by the end of the recovery period, the mean body weight for males was only 5% less (P<=0.05), and for females only 3% less (P<=0.05), than their respective control groups.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Feed consumption by rats was initially reduced between 19 and 26% in animals consuming the 1.5% diet relative to that of the control group. From day 4 to the end of the treatment period for that group, the average feed consumption was 3±5% lower in males, and 8± 10% lower in females when compared with their respective control groups. No differences in feed consumption were seen for the 0.1 and 0.5% groups or for the 1.5% recovery group 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:

no effects observed

Description (incidence and severity):

Minor red blood cell differences (reductions in mean corpuscular haemoglobin and mean corpuscular volume) were observed at the 0.5 and 1.5% dose levels for male and female rats. These differences were minimal, however, and did not indicate clinically significant changes in red blood cell indices.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Cholesterol levels were higher than the control values (P<=0.05) for all male rat test groups. After 28 days of recovery, cholesterol levels for male rats (1.5% group) were comparable to control values. The only other change in serum chemistry was an increase in albumin in male rats fed 1.5% EHA; this value returned to control levels after 28 days of recovery.

Urinalysis findings:

no effects observed

Description (incidence and severity):

No clinically significant treatment-related urinalysis changes were observed.

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Mean relative (to body weight) liver weights for all groups of animals receiving 0.5% or 1.5% EHA were greater (P<=0.05) than the weights of the respective control groups. The mean absolute liver weights for all groups fed 1.5% EHA, and for female rats fed 0.5% EHA were also significantly greater (P<=0.05) than for the respective control groups. No other changes in liver weights were noted and following 28 days of recovery, all absolute liver weights were comparable to control values. Absolute kidney weights for rats were unaffected by EHA treatment. In female rats, however, greater relative kidney weights were noted for both the 1.5 and 0.5% diet groups. Greater relative kidney weight differences were reflective of lower body weights for the 1.5% groups rather than indicative of any particular effect on the kidney. Minor, yet statistically significant (P<=0.05) decreases in absolute brain weights (1.5% female rats) were not considered biologically significant. In addition, while slight increases in relative adrenal gland, brain, and testes weights occurred for some of the groups, the differences were related to reduced terminal body weight and, therefore, were not considered to be indicative of organ specific toxicity.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No treatment-related gross pathology was observed for either main-study or recovery animals.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Hepatocyte hypertrophy was observed after 13 wk of treatment in rats. The hepatocyte hypertrophy occurred in males and females fed 1.5% EHA, and in male rats fed 0.5% EHA, but with decreased incidence and severity. The number of EHA-treated animals with hepatocyte cytoplasmic vacuolization decreased as both the EHA dose and incidence of hypertrophy increased. No hepatic lesions were observed in rats after recovery. Renal changes were not observed for rats. No testicular changes were noted.

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY: no mortality was observed during the study. Clinical abnormalities were minimal during the main 90-day study and the recovery period. Porphyrin tears, porphyrin nasal discharge, facial wounds, urine stained hair, and alopecia were observed without any relationship to treatment group. These abnormalities were transient and had no impact on the study.

BODY WEIGHT AND WEIGHT GAIN: No treatment-related differences for body weight or feed consumption were observed between controls and 0.5 and 0.1% males and females.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Feed consumption was reduced for both the recovery and non-recovery 1.5% animals of both sexes during the first 4 days of the study and generally remained lower than that of the controls throughout the treatment period. This reduction resulted in a slightly decreased rate of body weight gain for all animals receiving the 1.5% 2-EHA diets. At the end of the 90-day treatment period, the body weights of the 1.5% males and females were 8 and 10% (non-recovery) and 9 and 8% (recovery) lower than controls, respectively. During the recovery period, the mean consumption of basal diet for the recovery animals increased to levels equal to or slightly higher than that of controls. This increase resulted in an increase in body weight gain. By the end of the recovery phase, the body weights were only 5 and 3% lower than controls for males and females, respectively, and the difference for the females was no longer statistically significant.

FOOD EFFICIENCY: not examined

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study):not examined

OPHTHALMOSCOPIC EXAMINATION: No ophthalmologic abnormalities were observed in any recovery or non-recovery animal in the pre-study examination or in the five males and five females from each non-recovery dose group when they were examined during the last week of test article exposure.

HAEMATOLOGY: Minor hematologic differences involving red blood cells were observed at the 0.5 and 1.5% dose levels for both males and females. These included lower mean corpuscular volume in the 1.5% non-recovery and recovery females; lower mean corpuscular hemoglobin in the 0.5 and 1.5% non-recovery males, 1.5% recovery males, and 1.5% non-recovery females; and lower hemoglobin concentration in the 0.5% non-recovery females. The significance of these differences is obscure since all of the differences are minimal, the differences do not indicate any clinically significant change in the blood picture of the animals, and none of the changes were accompanied by evidence of anemia.

CLINICAL CHEMISTRY: The principal effects of the test article involved the liver. Exposure to 2-EHA resulted in a dose-dependent increase of cholesterol for males at all dose levels. Cholesterol levels for the males on the 0.1, 0.5, and 1.5% diets were increased 25, 42, and 78% relative to the controls. A similar change was not observed for cholesterol levels in females. Following the recovery period, cholesterol levels returned to normal. Triglycerides were not similarly altered. The alteration in cholesterol levels in males only may indicate a normal sex-dependent difference in fatty acid metabolism, since 2-EHA in the diet may act as a nutrient. Increased albumin concentrations in the serum may also indicate an effect on the liver; this difference was seen only at 1.5% 2-EHA in males and was not seen after the recovery period.

URINALYSIS: Urine volume was reduced for all females given 2-EHA for 90 'days and urine specific gravity was slightly increased for the 1.5% females. Similar effects were not observed for the males or for the females examined after the recovery period. Most significantly, urine osmolality did not differ between animals given 2-EHA and controls, indicating that 2-EHA did not interfere with the ability of the kidney to concentrate urine. Serum urea nitrogen levels were marginally higher than controls only for the 1.5% males at 90 days; at the end of the recovery period a similar difference was not present. The difference in urea nitrogen was not a clinically significant elevation.

ORGAN WEIGHTS: The absolute liver weights of the 0.5 and 1.5% animals after 90-days of 2-EHA exposure were 6 and 32% (males) and 7 and 19% (females) higher than those of the controls. This increase occurred in spite of the reduced body weight of the 1.5% animals. Liver weights relative to body and brain weights were also greater at the two higher doses. These effects were all statistically significant except for the absolute liver weights and liver/brain weights for the 0.5% male group. After the recovery period, the effect on liver weight was largely reversed except that the liver/body weight difference persisted for the 1.5% males. Weight differences observed in other organs were also likely to be related to growth retardation rather than toxicity. The weight differences observed in the brain are consistent with those seen in animals in which growth has been retarded. This difference was no longer evident in the 1.5% females by the end of the recovery period, but was still evident in the 1.5% males. The higher mean relative testes/body weights observed for the 0.5 and 1.5% males were consistent with effects observed in animals in which body growth has been retarded but testicular growth has been spared; the difference was still present in the 1.5% recovery males.

GROSS PATHOLOGY: No treatment-related changes were observed in non-recovery or recovery animals at the time of necropsy at any dose level for either sex.

HISTOPATHOLOGY: NON-NEOPLASTIC: At necropsy, the livers from treated animals were indistinguishable from the controls at 90 days and after the recovery period. Histologic examination of the livers revealed hypertrophy of the hepatocytes and a reduction of the number of small cytoplasmic vacuoles in hepatocytes from males and females fed 1.5% 2-EHA for 90 days and males fed 0.5% for the same length of time. The severity of both lesions was dose-dependent. Hepatocyte hypertrophy and decreased hepatocyte vacuolization were not seen following the recovery period indicating that these were reversible effects.

HISTOPATHOLOGY: NEOPLASTIC (if applicable): Minimal hyperplasia of bile ducts was found at both the 0.0 and 1.5% dose level in both sexes of recovery animals. The incidence for males was 4 of 10 at 1.5% versus 1 of 10 in the controls, and for females was 1 of 10 at 1.5% versus 3 of 10 at 0.0%. Bile duct hyperplasia was considered minimal when no more than three groups of newly formed ducts were observed in any of the liver sections. Because hyperplasia of this type and severity has been observed in control rats in other studies and because the incidence of hyperplasia can vary considerably, the differences in frequency of bile duct hyperplasia observed in this study were not considered biologically significant.

Dose descriptor:

NOAEL

Effect level:

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

Sex:

male

Basis for effect level:

other: growth retardation

Dose descriptor:

NOAEL

Effect level:

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

Sex:

female

Basis for effect level:

other: growth retardation

Dose descriptor:

NOEL

Effect level:

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

Sex:

female

Basis for effect level:

other: liver enlargement; considered primarily an adaptive change rather than a toxic effect.

Critical effects observed:

not specified

Conclusions:

The no-observed-adverse-effect-level (NOAEL) was considered to be 0.5% 2-EHA in the diet or 303 mg/kg/day for the males and 360 mg/kg/day for the females. This NOAEL was based on growth retardation at the highest dose level. The no-observed-effect-level (NOEL) for liver enlargement was considered to be 0.1% 2-EHA in the diet or 71 mg/kg/day for the females; liver enlargement was considered primarily an adaptive change rather than a toxic effect. There was no NOEL for males defined based on the increased cholesterol levels observed at all treament levels. Recovery following exposure to 2-EHA in the diet was essentially complete after 28 days. The 5% difference in mean body weight between the control and the 1.5% males at the end of the recovery period was the only effect which had not completely reversed.

Executive summary:

Groups of 10 male and 10 female rats were fed diets containing 2-ethylhexanoic acid (2-EHA) at concentrations of 0.0, 0.1, 0.5, or 1.5% for 90 days. Additional groups of 10 male and 10 female rats were fed either 0.0 or 1.5% 2-EHA for 90 days followed by a 28-day recovery (non-treatment) period. The control diet and the three 2-EHA diets provided dose levels of 0, 61, 303, or 917 mg/kg/day for males and 0, 71, 360, or 1068 mg/kg/day for females. Consumption of 2-EHA diets did not result in mortality, significant clinical abnormalities, or ophthalmologic abnormalities.

The 1.5% diet resulted in reduced feed consumption for male and female rats. During the recovery period, feed consumption in the group previously administered the 1.5% diet increased to a level comparable with or higher than controls. The lower two concentrations of diet did not alter feed consumption. The 1.5% diet was associated with reduced body weight gain. Mean body weight was 8% (males) and 10% (females) less than the control body weight for the non-recovery animals at the end of the treatment period. Similarly, mean body weight was 9% (males) and 8% (females) less for the recovery animals at the end of the treatment period. At the end of the 28-day recovery period, the body weights for the 1.5% males and females, respectively, were 5% and 3% lower than controls. The mean body weights for the 0.5 and 0.1% males and females were comparable to controls.

Slight hematologic differences involving red blood cells were observed at the 0.5 and 1.5% dose levels for both males and females, but these changes did not indicate any clinically significant change.

The principal effects of the test article involved the liver or metabolic processes associated with the liver. The 0.5 and 1.5% diets were associated with increased liver weight and histologic changes including hypertrophied hepatocytes and hepatocytes with reduced cytoplasmic vacuolization. Cholesterol levels were increased at all dose levels in males, but not in females. Liver effects were reversible upon removal of 2-EHA from the diet. At the end of the recovery period, only the liver weight relative to body weight for the males was statistically significant; this difference was due to lower body weights for the males. Cholesterol returned to normal levels during the recovery period.

Urinalysis results were unremarkable except for decreased urine volume for all groups of treated females and increased urine specific gravity for the 1.5% females after the 90-day treatment period. Urine osmolality was comparable between treated and control groups, indicating that the kidneys were able to concentrate urine normally. At the end of the recovery period, no differences were observed between treated and control animals. Male rats did not have similar differences at either collection time.

Kidney, testes, and brain weight differences were observed, but the differences were most likely a reflection of lower mean body weight, rather than target organ effects. Adrenal and ovarian weights were not altered by 2-EHA exposure.

The no-observed-adverse-effect-level (NOAEL) was considered to be 0.5% 2-EHA in the diet or 303 mg/kg/day for the males and 360 mg/kg/day for the females. This NOAEL was based on growth retardation at the highest dose level. The no-observed-effect-level (NOEL) for liver enlargement was considered to be 0.1% 2-EHA in the diet or 71 mg/kg/day for the females; liver enlargement was considered primarily an adaptive change rather than a toxic effect. There was no NOEL for males defined based on the increased cholesterol levels observed at all treament levels. Recovery following exposure to 2-EHA in the diet was essentially complete after 28 days. The 5% difference in mean body weight between the control and the 1.5% males at the end of the recovery period was the only effect which had not completely reversed.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Read Across to an analogue based on structural similarity. An analogue justification is attached to section 13 of the dataset.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Clinical signs:

no effects observed

Mortality:

no mortality observed

Description (incidence):

There were no mortalities during the 13-week study period.  

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Mean body weight gain was reduced more than 10% in animals receiving the 7500 ppm diet, relative to control animals.  However, average daily feed  consumption at 7500 ppm was higher than that of the control group.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

70-100% of rats receiving the 3800 or 7500 ppm diets had gross distention of the cecum and reddened gastric mucosa, although no compound-related  histopathologic effects were observed in the cecum, stomach, or any other  tissues examined.

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

There were no mortalities during the 13-week study period.  

Mean body  weight gain was reduced more than 10% in animals receiving the 7500 ppm diet, relative to control animals.  However, average daily feed  consumption at 7500 ppm was higher than that of the control group.

70-100% of rats receiving the 3800 or 7500 ppm diets had gross distention  of the cecum and reddened gastric mucosa, although no compound-related  histopathologic effects were observed in the cecum, stomach, or any other  tissues examined.

Dose descriptor:

NOEL

Remarks:

local effects

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: gross pathology stomach and caecum

Dose descriptor:

NOEL

Remarks:

local effects

Effect level:

1 900 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: gross pathology stomach and caecum

Dose descriptor:

NOAEL

Remarks:

systemic effects

Effect level:

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

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

Dose descriptor:

NOAEL

Remarks:

systemic effects

Effect level:

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

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

Dose descriptor:

NOAEL

Remarks:

systemic effects

Effect level:

3 800 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

Critical effects observed:

not specified

Based on the results of the 13-weeks study, doses of 1000 and 2000 ppm stannous chloride in feed were selected for the chronic 105-week study.

Conclusions:

In a 13-week repeated dose study with F344/N rats, 70 to 100% of rats receiving the 3800 or 7500 ppm diets had gross distention of the cecum and reddened gastric mucosa, although no compound-related histopathologic effects were observed in the cecum, stomach, or any other tissues examined. A NOEL of 1900 ppm (187 mg/kg bw/day) was determined based on the effects seen at 3800 ppm.
Based on the results of the 13-week study, doses of 1000 and 2000 ppm stannous chloride in feed were selected for the chronic, 105-week study.

Executive summary:

A thirteen-week study was conducted to evaluate the cumulative toxicity of stannous chloride and to determine the concentrations of stannous chloride to be used in chronic studies. Male and female F344/N rats were fed diets containing 0, 500, 1000, 1900, 3800 or 7500 ppm. 70 to 100% of rats receiving the 3800 or 7500 ppm diets had gross distention of the cecum and reddened gastric mucosa, although no compound-related histopathologic effects were observed in the cecum, stomach, or any other tissues examined. A NOEL of 1900 ppm (187 mg/kg bw/day) was determined based on the effects seen at 3800 ppm.

Based on the results of the 13-week study, doses of 1000 and 2000 ppm stannous chloride in feed were selected for the chronic, 105-week study.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Study duration:

subchronic

Species:

rat

System:

hepatobiliary

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

Tin bis(2 -ethylhexanoate), stannous chloride and EHA have all been evaluated in repeat-dose subacute oral toxicity studies in rats. These studies have been assigned a K-2 evaluation. All three materials had a low order of toxicity in these study protocols. Body weight gain depression was seen at 750 or 800 mg/kg/d doses, while a dose of 3000 mg/kg/d was needed to cause body weight depression for stannous chloride. In these studies, none of the three substances caused serious target organ toxicity even at very high doses. EHA caused slight effects in liver but only at a dose of 2728 mg/kg, males and 3139 mg/kg, female; tin bis(2 -ethylhexanoate) did not have target organ effects including liver and kidney, but doses in this study only went as high as 750 mg/kg/d. No pathology was noted for stannous chloride, but liver and kidney were not weighed or evaluated for histopathology in this study. For the three test substances, the LOAELs ranged between 706 -1608 mg/kg; NOAELs ranged between 250- 706 mg/kg/d.

Subchronic repeated-dose (90 day) studies are available for the two hydrolysis products of tin bis(2 -ethylhexanoate), stannous chloride and ethylhexanoic acid. These studies reported a decrease in body weight gain at higher doses for both materials and mild effects on liver and kidney weights and liver histopathology for EHA only. The liver effects for EHA were considered to be adaptive in nature and not toxic effects. The NOAELs for both materials were nearly the same, 300 mg/kg/d.

Justification for classification or non-classification

For the subacute oral toxicity studies on tin bis(2 -ethylhexanoate) and the two hydrolysis products all three materials had a low order of toxicity.

In subchronic studies on the two hydrolysis products, a decrease in body weight gain at higher doses for both materials and mild effects on liver and kidney weights and liver histopathology for EHA only were observed. The liver effects for EHA seen in subchronic studies were considered to be adaptive in nature and not toxic effects. No repeated dose classification is necessary according to Regulation (EC) No 1272/2008.