Dibutyl hydrogen phosphate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

In an OECD combined repeat dose and reproductive/developmental toxicity screening test 10 male and 10 female rats per group were administered doses of 0, 30, 100, 300 or 1000 mg/kg bw of the test substance per gavage. The NOEL for parental toxicity was determined with 30 mg/kg bw for both sexes, based on epithelial hyperplasia accompanied by degeneration and ulceration of the urinary bladder mucosa. The NOEL for reproductive toxicity was determined with 1000 mg/kg bw/day for both sexes.

Additional information: In a 2-generation study with tributyl phosphate (not included in this dataset) there was no evidence of reproductive toxicity, of reproductive organ pathology, or effects on gestation or lactation at any dose tested. The NOAEL for reproductive toxicity was determine with the highest dose tested of at least 3000 ppm (approx. 225 mg/kg bw/day).
Tributyl phosphate undergoes a rapid metabolisation to dibutyl hydrogen phosphate by the microsomal enzyme complex in the liver and can therefore be used as a surrogate for dibutyl hydrogen phosphate. For details see chapter 7.1 (Toxicokinetics, metabolism and distribution).

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP guideline study (OECD combined repeat dose and reproductive/developmental toxicity screening test)

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on species / strain selection:

Crj:CD (SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: males: 331-262 g; females: 192-215 g

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +- 3
- Humidity (%): 55 +- 10
preliminary reproduction toxicity screening test performed as dose range finder with doses of 0, 50, 100, 200, 500, and 1000 mg/kg bw/day

Route of administration:

oral: gavage

Vehicle:

other: sesame oil

Details on mating procedure:

Male and female animals were exposed to the test substance 14 days before mating.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Exposure period: 44 days (male) and from 14 days before mating to day 3 of lactation (females).

Frequency of treatment:

once daily

Details on study schedule:

Males were sacrificed on day 45. Females were sacrificed on day 4 of lactation.

Dose / conc.:

30 mg/kg bw/day (nominal)

Dose / conc.:

100 mg/kg bw/day (nominal)

Dose / conc.:

300 mg/kg bw/day (nominal)

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

10 male and 10 female animals per dose

Control animals:

yes, concurrent vehicle

Parental animals: Observations and examinations:

MORTALITY: Yes

CLINICAL SIGNS: Yes

BODY WEIGHT: Yes
- Time schedule for examinations:
males: days 1, 8, 15, 22, 29, 36, and 43/44
females: days 1, 8, 15 (days of premating); days 0, 7, 14, 20 (days of pregnancy); days 0 and 4 (days of lactation)

for further information see chapter 7.8.1 (reference to same study)

Litter observations:

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
number and sex of pups, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities

GROSS EXAMINATION OF DEAD PUPS:
yes, for external and internal abnormalities

Postmortem examinations (parental animals):

see IUCLID chapter 7.5.1
plus: histopathology of reproductive organs (e.g. ovary)

Postmortem examinations (offspring):

external anomalies and visceral anomalies

Reproductive indices:

copulation index, fertility index, implantation index, gestation index, delivery index

Offspring viability indices:

live birth index, viability index

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

red urine in 4 males at 100 mg/kg, 7 males at 300 mg/kg, and 5 male survivors at 1000 mg/kg bw

Mortality:

mortality observed, treatment-related

Description (incidence):

3 males and 2 females died in the 1000 mg/kg bw group.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight gain significantly decreased in males at 1000 mg/kg bw/day (about -14% at termination) - see figures 1 and 2 attached

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Decrease in food consumption at >= 100 mg/kg bw (males).

Haematological findings:

no effects observed

Description (incidence and severity):

No effects on urinary, hematological and blood chemical findings in the males (females not given).

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Description (incidence and severity):

No effects on urinary, hematological and blood chemical findings in the males (females not given).

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Histopathology showed epithelial hyperplasia accompanied by degeneration and ulceration of the urinary bladder mucosa in males and females treated with >= 100 mg/kg bw. Epithelial hyperplasia and hyperkeratosis of the forestomach (some with erosion and ulceration in the gastric mucosa) were noted in both sexes >= 300 mg/kg bw - see Tables 3 and 4 attached

Reproductive function: oestrous cycle:

not specified

Reproductive function: sperm measures:

not specified

Reproductive performance:

no effects observed

The parental animals exhibited no significant effects on reproductive parameters including copulation index, fertility index, numbers of corpora lutea and implantation sites, gestation index and gestation lenghts - see Table 5 attached

Key result

Dose descriptor:

NOEL

Effect level:

30 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: maternal toxicity

Key result

Dose descriptor:

NOEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: fertility

Remarks on result:

other: The parental animals exhibited no significant effects on reproductive parameters including copulation index, fertility index, numbers of corpora lutea and implantation sites, gestation index and gestation lengths.

Key result

Critical effects observed:

no

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

the number of pups alive on day 4 of lactation was reduced in the 1000 mg/kg bw group compared to control (in male pups not significant; in female pups significant (p<0.05)) - see Table 6 attached

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

body weight on day 0 of male and female pups in 1000 mg/kg bw group lower than control (not significant) - see Table 6 attached

Gross pathological findings:

no effects observed

Description (incidence and severity):

no treatment related external or visceral anomalies - see Table 7 attached

Key result

Dose descriptor:

NOEL

Generation:

F1

Effect level:

300 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

viability

other: The number of live pups and the viability index on day 4 of lactation decreased with 1000 mg/kg.

Key result

Critical effects observed:

no

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

300 mg/kg bw/day

Treatment related:

yes

Relation to other toxic effects:

not specified

Dose response relationship:

yes

The parental animals exhibited no significant effects at dosages of 30, 100, 300, or 1000 mg/kg bw/day on reproductive parameters including copulation index, fertility index, numbers of corpora lutea and implantation sites, gestation index, gestation lenght, absolute and relative weight of examined reproductive organs and histopathological findings.

Executive summary:

In an OECD combined repeat dose and reproductive/developmental toxicity screening test 10 male and 10 female rats per group were administered doses of 0, 30, 100, 300 or 1000 mg/kg bw of the test substance per gavage. Administration period for males were 44 days , and for females, from 14 days before mating to day 3 of lactation. Absolute and relative reproductive organ weight and reproductive parameters were determined.

Maternal toxicity became obvious as body weight gain decrease in males and mortality of 3 males and 2 females in the 1000 mg/kg bw groups. No effects on urinary, hematological and blood chemical findings in the males (females not given). Histopathology showed epithelial hyperplasia accompanied by degeneration and ulceration of the urinary bladder mucosa in males and females with >= 100 mg/kg bw. Epithelial hyperplasia and hyperkeratosis of the forestomach (some with erosion and ulceration in the gastric mucosa) were noted in both sexes >= 300 mg/kg bw. Increase of absolute and relative liver weight and hepatocellular swelling in females with 1000 mg/kg bw. NOEL for maternal toxicity was thus determined with 30 mg/kg bw for both sexes.

The parental animals exhibited no significant effects at dosages of 30, 100, 300, or 1000 mg/kg bw/day on reproductive parameters including copulation index, fertility index, numbers of corpora lutea and implantation sites, gestation index, gestation length, absolute and relative weight of examined reproductive organs and histopathological findings. The NOEL for reproductive toxicity is therefore 1000 mg/kg bw/day for both sexes.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

The materials/methods and results are described in detail und are sufficient for evaluation.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

In the combined repeated dose and reproductive/developmental toxicity test according OECD 422 technical dibutyl hydrogen phosphate (purity: 62.6%, other contents: monoester 18.3%, triester and other 19.1%) was administered by gavage to rats in doses of 0, 30, 100, 300, or 1000 mg/kg bw/day. Male rats received the test substance 2 weeks before mating, during the 2 weeks mating period and 2 weeks afterwards. Female rats received the test substance 4 weeks before mating and until day 3 after delivery.
Maternal toxicity became obvious as body weight gain decrease in males and mortality of 3 males and 2 females in the 1000 mg/kg bw groups. No effects on urinary, hematological and blood chemical findings in the males (females not given). Histopathology showed epithelial hyperplasia accompanied by degeneration and ulceration of the urinary bladder mucosa in males and females with >= 100 mg/kg bw. Epithelial hyperplasia and hyperkeratosis of the forestomach (some with erosion and ulceration in the gastric mucosa) were noted in both sexes >= 300 mg/kg bw. Increase of absolute and relative liver weight and hepatocellular swelling in females was observed at 1000 mg/kg bw/day. The NOEL for parental toxicity was thus determined with 30 mg/kg bw for both sexes.
The parental animals exhibited no significant effects at all dosages on reproductive parameters including copulation index, fertility index, numbers of corpora lutea and implantation sites, gestation index, gestation length, absolute and relative weight of examined reproductive organs and histopathological findings. The NOEL for reproductive toxicity is therefore 1000 mg/kg bw/day for both sexes.

Additional data are available for tributyl phosphate (obtained from OECD SIS for tributyl phosphate CAS 126-73-8, UNEP Publication, 2001):
‘A two-generation reproductive toxicity study (not included in the dataset) has been conducted with Sprague-Dawley rats. Rats were fed tributyl phosphate in the diet at 200, 700, or 3000 ppm (approx. 15, 53, or 225 mg/kg bw/day). There was no evidence of reproductive organ histopathology and no effects on pre- or post-natal mortality at any dose. In adults, dose levels of 700 and 3000 ppm produced reductions in body weights, body weight gain, and food consumption during the F0 and F1 pre-breeding dosing periods. The 200 ppm feeding level produced transient effects on body weight and food consumption in adults and also reduced the body weights of pups. The only treatment related postnatal effect was reduced pup weights in the high dose group, which was associated with maternal toxicity. Based on these effects, the reproductive toxicity NOAEL for tributyl phosphate was >3000 ppm (according to 225 mg/kg bw/day), while the maternal toxicity NOAEL and post-natal toxicity NOAEL were both less than 200 ppm.
This study provides an adequate basis for evaluating the reproductive toxicity of tributyl phosphate. The NOAEL for reproductive toxicity is >3000 ppm, a level over ten-fold higher than the general systemic level that caused pup effects and adult toxicity (<200 ppm). These findings indicate that tributyl phosphate is not a reproductive toxicant in the absence of maternally toxicity.’

Effects on developmental toxicity

Description of key information

In the key-study pregnant rats were treated orally with dibutyl hydrogen phosphate (250, 500, 1000 mg/kg bw/day) on days 7-17 of gestation. Cesarean sections were performed on day 20 of gestation. The fetuses did not show external, visceral or skeletal abnormalities.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: scientifically acceptable and sufficient documented (Original in Japanese)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Pregnant rats were treated orally with dibutyl hydrogen phosphate (250, 500, 1000 mg/kg bw/day) on days 7-17 of gestation. Cesarean sections were performed on day 20 of gestation. The fetuses were examined for external, visceral or skeletal abnormalities.

GLP compliance:

not specified

Species:

rat

Strain:

Wistar

Route of administration:

oral: gavage

Vehicle:

olive oil

Remarks:

2 mL/kg bw

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

no data

Duration of treatment / exposure:

day 7-17 of gestation

Frequency of treatment:

daily

Duration of test:

day 20 of gestation (cesarean section)

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

14 dams (vehicle)
11 dams test item/dose

Control animals:

yes, concurrent vehicle

Maternal examinations:

body weight and food consumption
organ weights: liver, kidneys, spleen thymus, gravid uterus admusted body weight gain
no. of pregnant females
no. of dams with living fetuses
no. of dams with total resorption
no. of dead dams

Ovaries and uterine content:

no. of corpora lutea
no. of implants
Indicence of dead or resorbed fetuses

Fetal examinations:

no. of living fetuses
sex ratio
body weight of living fetuses
external, skeletal, visceral observations

Statistics:

yes

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

the adjusted body weight gain (without gravid uterus weight) was reduced in the high dose group by 22% (see Table 1 attached); not statistically significant

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

no significant changes in weights of organs: liver, kidneys, spleen, thymus gravid uterus

Details on maternal toxic effects:

no treatment related effects on no. of corpora lutea, incidence of dead or resorbed fetuses (early and late stage), no. of living fetuses and sex ratio (see Table 2 attached)

Dose descriptor:

NOAEL

Effect level:

> 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Remarks on result:

other: not statistically significant lower adjusted body weight gain at 1000 mg/kg bw/day

Dose descriptor:

NOAEL

Effect level:

> 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Abnormalities:

no effects observed

Fetal body weight changes:

no effects observed

Description (incidence and severity):

see Table 2 attached

Changes in sex ratio:

no effects observed

Description (incidence and severity):

see Table 2 attached

External malformations:

no effects observed

Description (incidence and severity):

see Table 3 attached

Skeletal malformations:

no effects observed

Description (incidence and severity):

see Table 3 attached

Visceral malformations:

no effects observed

Description (incidence and severity):

see Table 3 attached

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: develpmental toxicity

Remarks on result:

other: The fetuses from dams receiving dibutyl hydrogen phosphate showed no evidence of external, visceral or skeletal abnormalities.

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

no

The fetuses from dams receiving dibutyl hydrogen phosphate showed no evidence of external, visceral or skeletal abnormalities. Dibutyl hydrogen phosphate caused no maternal of fetal toxicities in any dibutyl hydrogen phosphate treated group.

Conclusions:

The fetuses from dams receiving dibutyl hydrogen phosphate showed no evidence of external, visceral or skeletal abnormalities. Dibutyl hydrogen phosphate caused no maternal of fetal toxicities in any dibutyl hydrogen phosphate treated group.

Executive summary:

Pregnant rats were treated orally with dibutyl hydrogen phosphate (250, 500, 1000 mg/kg bw/day) on days 7-17 of gestation. Cesarean sections were performed on day 20 of gestation. The fetuses were examined for external, visceral or skeletal abnormalities.

Dibutyl hydrogen phosphate caused no maternal toxicity, besides a reduced body weight gain in the highest dose group (not statistically significant). No effects on pregnancy parameters were affected. The fetuses showed no evidence of treatment related toxicity with regard to body weight, sex ration, external, visceral or skeletal abnormalities in any dibutyl hydrogen phosphate treated group. Under the conditions of this study, the no-observed-adverse-effect levels (NOAEL) for maternal and fetal toxicities were considered to be more than 1000 mg/kg bw/day.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Quality of whole database:

The materials/methods and results are described in detail und are sufficient for evaluation.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

Pregnant rats were treated orally with dibutyl hydrogen phosphate (250, 500, 1000 mg/kg bw/day) on days 7-17 of gestation. Cesarean sections were performed on day 20 of gestation. The fetuses were examined for external, visceral or skeletal abnormalities. Dibutyl hydrogen phosphate caused no maternal toxicity, besides a reduced body weight gain in the highest dose group (not statistically significant). No effects on pregnancy parameters were affected. The fetuses showed no evidence of treatment related toxicity with regard to body weight, sex ration, external, visceral or skeletal abnormalities in any dibutyl hydrogen phosphate treated group. Under the conditions of this study, the no-observed-adverse-effect levels (NOAEL) for maternal and fetal toxicities was considered to be more than 1000 mg/kg bw/day.

 

In an OECD combined repeated dose and reproductive/developmental toxicity screening test 10 male and 10 female rats per group were administered doses of 0, 30, 100, 300 or 1000 mg/kg bw of the test substance per gavage. Administration period for males were 44 days, and for females, from 14 days before mating to day 3 of lactation.

Distinct maternal toxicity was observed with mortality of 3 males and 2 females in the high dose group (1000 mg/kg bw/day). The NOEL for maternal toxicity was 30 mg/kg bw in this study, based on effects in the bladder and forestomach.

The parental animals exhibited no significant effects on reproductive parameters including copulation index, fertility index, numbers of corpora lutea and implantation sites, gestation index and gestation lengths. The number of live pups and the viability index at 1000 mg/kg bw was decreased, attributable to a high incidence of fatalities of pups in some litters at or after birth.

The NOELs for reproductive performance are considered to be 1000 mg/kg bw/day for both sexes, and 300 mg/kg bw/day for offspring development.

Toxicity to reproduction: other studies

Additional information

No data.

Justification for classification or non-classification

Due to the results of the combined repeated dose and reproductive/developmental toxicity test equivalent or similar to OECD 422 and the developmental toxicity study with dibutyl hydrogen phosphate in rats according to CLP classification criteria (Regulation (EC) No 1272/2008) a classification is not justified.

This conclusion is supported by the 2-generation study and developmental toxicity studies with tributyl phosphate as a surrogate for dibutyl hydrogen phosphate.