Diisobutyl phthalate

Repeated dose toxicity: oral

Administrative data

Endpoint:

repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, guideline study, animal experimental study with minor restrictions, fully adequate for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Materials and methods

Principles of method if other than guideline:

Subchronic toxicity study with perinatal exposure in which pups from dams exposed during pregnacy and lactation were treated for an additional 13 wk post-weaning

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dibutyl phthalate

EC Number:

201-557-4

EC Name:

Dibutyl phthalate

Cas Number:

84-74-2

IUPAC Name:

dibutyl phthalate

Details on test material:

Dibutyl phthalate (Lot L-121 1-83) was obtained from Chem Central (Kansas City, MO). Initia l
identity and purity analysesconformed it to be 9.8%

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Administration / exposure

Route of administration:

oral: feed

Details on oral exposure:

The exposure concentrations selected for the 13-week studies with no perinatal exposure were based on the results for rat dams used in the MPE determination study; in the 13-week studies, groups of 10 rats per sex were administered 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm dibutyl phthalate and groups of 10 mice per sex were administered
0, 2500, 5,000, 10,000, 20,000 or 40.000 ppm dibutyl phthalate in feed 7 days a week for 13 weeks.
The dose levels equated to
0 , 176, 359, 720, 1540 and 2964 mg/kg/day for males and
0, 178, 356, 712, 1413 and 2943 mg/kg/day for females

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Stability studies performed by MRI on Lot C100682 on a gas chromatographic system with an FID indicated that dibutyl phthalate is stable as a bulk chemical for 2 weeks when stored protected from light at temperatures up to 60 C. Throughout the studies, dibutyl phthalate was stored at room temperature; periodic reanalyses performed by the study laboratory with infrared spectroscopy, gas chromatography, and ester hydrolysis titration indicated no decomposition of the bulk chemical.

Duration of treatment / exposure:

13 weeks 7 days/ week

Frequency of treatment:

Continous

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm dibutyl phthalate
Basis:
nominal in diet

Doses / concentrations 2

Remarks:

Doses / Concentrations:
Equivalent to 0, 176, 359, 720, 1,540 and 2,964 mg/kg bwt for males
Basis:
nominal in diet

Doses / concentrations 3

Remarks:

Doses / Concentrations:
Equivalent to 0, 178, 356, 712, 1,413 and 2,943 mg/kg bwt for females
Basis:
nominal in diet

No. of animals per sex per dose:

10

Control animals:

yes, plain diet

Positive control:

None

Examinations

Sacrifice and pathology:

Complete necropsies were performed on all animals. The following organs were weighed: heart, right kidney, liver, lungs, right testis, and thymus.
Histopathologic evaluations were performed on all animals in the control and highest exposure groups. The tissues routinely examined were the same as in the 13 weeks study with perinatal exposure. Gross lesions of rats and mice in all our exposure groups are examined tissues examined in the lower exposure groups include the liver, and the testes of ratsand the liver of mice

Other examinations:

haematologyand clinical chemistry evaluation is evaluations were done at the end of the studies. Haematology and clinical chemistry parameters evaluated was the same as in the other 13 weeks studies with perinatal exposure.
Zinc and testosterone levels were measured in the sera and testes of all male rats. Sperm motility and vaginal cytology were performed in rats, up to the 20,000 ppm groups.
the livers of five male and five female rats a group were analysed for hepatic paroxysm proliferation and liver enlargement. By monitoring increases in peroxisomal parmitol-CoA activity andliver weight.

Results and discussion

Results of examinations

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Details on results:

Growth: statistically significantly decreased in both sexes at 20000 ppm BNP and above, and in males only at 10000 ppm.

Food intake: decreased for males and females at 40000 ppm in the diet (all animals were emaciated).

Haematology: statistically significantly decreased haemoglobin values and erythrocyte counts at 5000 ppm and above (males only); haematocrit values statistically significantly decreased at 20000 and 40000 ppm (males only); statistically significantly increased platelet count at 5000 ppm and above (males only); statistically significantly increased nucleated erythrocytes at 40000 ppm (both sexes).

Clinical chemistry: statistically significantly decreased cholesterol at 20000 and 40000 ppm (both sexes); statistically significantly, dose-related, decreased triglyceride levels in all treated males and in females at 10000 ppm and above; statistically significantly increased serum alkaline phosphatase in males at 20000 and 40000 ppm, and in females at 10000 and above; significantly increased serum bile acid concentration in males at 20000 and 40000 ppm and in females at 5000 ppm and above; dose-related, increased PCoA activity (cyanide-insensitive palmitoyl-CoA oxidase activity, an indicator of peroxisome proliferation) at 5000 ppm and above in both sexes.

Organ weights: statistically significantly increased relative liver and kidney weights in males at 5000 ppm and above and in females at 10000 and above; statistically significantly decreased testicular weights at 20000 and 40000 ppm.

Histopathology:
- liver: hepatocellular cytoplasmic alterations, consistent with glycogen depletion, at 10000 ppm and above (both sexes); fine, eosinophilic granules present at 40000 ppm, with an increased number of peroxisomes visible using electron microscopy; lipofuscin accumulation (both sexes) at 10000 ppm and above.
- testis: dose-related degeneration of germinal epithelium at 10000 ppm and above with almost complete loss of germinal epithelium at 40000 ppm;

Other:
- statistically significantly decreased testicular zinc and serum testosterone concentrations at 20000 and 40000 ppm; statistically significantly lower serum zinc at 40000 ppm.
- statistically significantly reductions in spermatid heads/testis and per g of testis, epididymal spermatozoal motility, and the number of epididymal spermatozoa per g epididymis at 20000 ppm and above.

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

177 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks:

in the diet

Sex:

male/female

Basis for effect level:

other: based on alterations in haematological parameters, serum chemistry and organ weights at 356-359 mg/kg bw/d

2

Dose descriptor:

NOAEL

Effect level:

359 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks:

in the diet

Sex:

male

Basis for effect level:

other: degeneration of germinal epithelium at 720 mg/kg bw/d

3

Dose descriptor:

NOAEL

Effect level:

177 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks:

in the diet

Sex:

male/female

Basis for effect level:

other: peroxisome proliferation-related changes in liver (increased PCoA activity) at 356-359 mg/kg bw/d

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

In a well conducted 13 week feeding study in rats with dIbutylphthalate, principle effects were seen in the liver and testis with an overall NOAEL og 177 mg/kg bw/d.

Executive summary:

The subchronic oral toxicity of dibutyl phthalate was investigated in groups of F344/N rats (n = 10/sex) fed diets containing 0, 2500, 5000, 10000, 20000 or 40000 ppm DBP. This was equivalent to approx. 0, 176, 359, 720, 1,540 or 2,964 mg/kg bw for males and approx. 0, 178,356, 712, 1,413 or 2,943 mg/kg bw for females. The overall NOAEL from this study was 2500 ppm DIB in the diet (equivalent to 177 mg/kg bw/d, both sexes) based on alterations in haematological, serum chemistry and organ weight values at 5000 ppm. The NOAEL for effects on testis (degeneration of germinal epithelium) was 5000 ppm (359 mg/kg bw/d). The NOAEL for peroxysome prolifearation-related changes (increased PCoA activity) was 2500 ppm in both sexes (177 mg/kg bw/d).