Triisobutyl phosphate

Endpoint summary

Description of key information

In a subchronic oral study (13 weeks) in rats a NOEL/NOAEL of 68.4 mg/kg bw in males and 84.3 mg/kg bw in females was observed. Effects observed at the next higher dose level were decreased food consumption, minor alterations of hematology parameters and clinical chemistry. However, the BAuA evaluated this study and concluded that the observed effects at the highest treatment level, 5000 mg/kg diet are not toxicological relevant. The BAuA therefore, decided that the dosis of 5000 mg/kg diet can be assumed to be a marginal LOEL which will only be slightly above the actual NOAEL. According to the BauA it can thus be assumed that for the estimation of an OEL, a NAEL of 2500 mg/kg diet, which corresponds to 170 mg/kg bw for male and 210 mg/kg bw for female rats, can be used.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Limit test:

no

Specific details on test material used for the study:

- Name of test material: Triisobutyl Phosphate (TIBP)
- Source: Monsanto Chemical Company, 800 North Lindbergh Boulevard, St. Louis, MO 63167
- EHL Substance Identification Code : T890095
- Physical state: Clear, slightly yellow liquid
- Analytical purity: 99.7% (weight)
- Lot/batch No.: 257790

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory, Portage MI
- Age at study initiation: Approximately six weeks
- Weight at study initiation: Males; 170.0 - 217.9 g. Females; 132.4 - 174.1 g.
- Fasting period before study: not specified
- Housing: Individual stainless steel cages with wire mesh bottoms suspended over paper bedding.
- Diet (e.g. ad libitum): Purina; Mills Certified RODENT CHOW #5002
- Water (ad libitum): St. Louis public water supply
- Acclimation period: Fifteen days (Assigned Lot Number; L89097)

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
The neat test miaterial was mixed thoroughly with the basal , diet using high speed mixers.

DIET PREPARATION
- Rate of preparation of diet: Approximately weekly
- Mixing appropriate amounts with (Purina Mills): T-1 (200 ppm);. T-2 (1000 ppm); T-3 (5000 ppm)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Stability of Neat Test Material: Analyses by gas chromatography using a nitrogen/phosphorus detector prior to the first use and after the last use
Diet Mixture Stability: Analysis of T-1 and T-3 level samples stored at room temperature (open container, 7 and 14 days) or kept frozen, closed container, 35 days)
Homogeneity of Diet Mixtures: Analysis of duplicate samples from top, middle and bottom of mixer of T-1 and T-3 diets prepared for the first week of the study
Dietary Level Verification: Gas chromatography with a nitrogen/phosphorus detector, all dietary levels for preparations 1 , 2 and 3; at least one level/week there after.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

continuous in diet

Dose / conc.:

200 ppm

Remarks:

nominal in diet
according to 13.9 mg/kg bw/day in males and 16.8 mg/kg bw/day in females

Dose / conc.:

1 000 ppm

Remarks:

nominal in diet
according to 68.4 mg/kg bw/day in males and 84.3 mg/kg bw/day in females

Dose / conc.:

5 000 ppm

Remarks:

nominal in diet
according to 346.1 mg/kg bw/day in males and 403.9 mg/kg bw/day in females

No. of animals per sex per dose:

160 (80 males, 80 females); plus 10/sex at pretest.
Groups consisted: 30/sex

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: not specified
- Rationale for animal assignment: Computer randomization by weight

Positive control:

No

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Checks for Mortality and Moribundity: Twice daily (AM and PM)

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once weekly

BODY WEIGHT: Yes
- Time schedule for examinations: Once weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, weekly
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes, weekly

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Once at pretest, and just prior, to terminal sacrifice
- Dose groups that were examined: All at pretest; all high level and control animals just prior to week 13 sacrifice

HAEMATOLOGY AND CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Pretest and at termination of test material administration
- Anaesthetic used for blood collection: Yes, osterior vena cava of C02-anesthetized
- Animals fasted: Yes
- How many animals: Ten/sex, pretest; ten/sex/level week-13

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
Animals Examined: All
Scheduled Sacrifices: Day 29, Days 91-92 and Day 147

HISTOPATHOLOGY: Yes
Tissues Examined: All retained tissues from control and T-3 levels

Statistics:

The following statistical procedures were used to detect statistically significant differences between treated animals and their respective controls:
- Dunnett's Multiple Comparison Test (two-tailed): Inlife body weights, cumulative body weight changes changes and food consumption
- EHL decision-tree analysis: Hematology data, clinical chemistry data, terminal body weights, absolute organ weights and organ/body weight ratios were evaluated by decision-tree statistical analyses which, depending on the results of tests for normality and homogeneity of variances (Bartlett's Test), utilized either parametric [Dunnett's Test and Linear Regression] or nonparametric [Kruskal-Wallis, Jonckheere's and/or Mann-Whitney Tests] routines to detect differences and analyze for trend.
- Fisher's Exact Test (one-tailed) with Bonferroni Inequality Procedure: Incidence of microscopic lesions
- Other statistical routines used for some data included Grubbs Test to detect outliers

Clinical signs:

no effects observed

Description (incidence and severity):

There were no clinical signs considered to be related to administration of the test material.

Mortality:

no mortality observed

Description (incidence):

There were no deaths in this study.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

There were no statistically significant differences in group mean body weights of treated animals when compared with controls at any time during the study.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

On a grams of food per day (GM/DAY) basis, there was decreased food consumption by both sexes at the highest dose level during the first week of the study (approximately 90% of control mean values for both sexes) and in high level females only during week 13. Food consumption by all treated groups was comparable to or greater than that of controls at all other times of the study.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

There were no lesions observed in treated animals in this study.

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

The only alteration of hematologic parameters considered possibly related to treatment was a decrease in neutrophil counts in T-3 level males (neutrophil counts in T-3 level females were also decreased but were not statistically different from controls). Increased MCH in T-3 level males and MCHC in T-2 and T-3 level males were also statistically different from controls. Changes in parameters (other than neutrophils) were small in magnitude, and in the absence of any other corraborative findings, were of doubtful toxicologic significance.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

The only clinical chemistry alteration considered possibly related to treatment was a statistically significant increase of cholesterol (mean value was 131% of control mean) in T-3 level males. Other small but statistically significant changes included increased chloride in T-3 level females and increased BUN in T-2 level animals of both sexes. These latter changes were not considered related to treatment due to their small magnitude or lack of dose-relationship.

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

There were no organ weight alterations (absolute and/or relative to body weight) considered related to treatment.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no gross necropsy findings considered related to treatment.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

There were no treatment related microscopic lesions observed.

Dose descriptor:

NOEL

Effect level:

210 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: The observed effects, seen at the highest dose level of 5000 mg/kg diet, could not conclusively be determined as toxicological relevant (acc BAuA evaluation of this study 2007).

Dose descriptor:

NOEL

Effect level:

170 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: The observed effects, seen at the highest dose level of 5000 mg/kg diet, could not conclusively be determined as toxicological relevant (acc BAuA evaluation of this study 2007).

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

68.4 mg/kg bw/day

Study duration:

subchronic

Species:

rat

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

Triisobutyl phosphate (TIBP) was administered to Sprague-Dawley rats at target exposure levels of 0, 200, 1000 or 5000 parts per million (ppm) in feed for approximately 13 weeks. (Monsanto, 1990) Following this, some animals in the 0 and 5000 ppm groups were given untreated feed for an approximately 8 week recovery period. Groups consisted of 30 rats/sex for the 0 and 5000 ppm dose levels and 10 rats/sex for the remaining levels. Clinical observations were performed weekly; body weights and food consumption were also determined weekly. Clinicopathologic examinations were performed pretest and at approximately 13 weeks. Ophthalmic exams were performed pretest and just prior to the week 13 sacrifice. All animals were sacrificed: 10/sex/dose were given a complete necropsy (gross examination, organ weights, and extensive tissue sampling) at 13 weeks, 10/sex in the 0 and 5000 ppm groups were given a gross necropsy and had only urinary bladder tissue sampled at approximately weeks 4 and 21. All retained tissues from the control and highest treatment levels were examined microscopically. Analyses to verify the stability of the test material (both neat and when mixed in the diet), the dietary homogeneity, and concentrations of the test material in the diet were performed with satisfactory results. Overall study averages for consumption of test material (mg TIBP/kilogram body weight/day), based on the target concentrations, were approximately 13.9, 68.4 and 346.1 in males and 18.8, 84.3 and 403.9 in females for the T-1, T-2 and T-3 levels, respectively.

Effects considered attributable to treatment were limited to transiently decreased food consumption and minor alterations of hematologic (a mild decrease in neutrophil counts) and clinical chemistry (increased cholesterol levels) parameters in males and/or females at the 5000 ppm level. There were no gross necropsy findings or microscopic lesions considered treatment related.

The NOEL/NOAEL was considered to be 1000 ppm (68.4 mg/kg bw in males and 84.3 mg/kg bw in females).

In 2007 the German Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (BAuA) has evaluated Triisobutyl phosphate to estimate an OEL (Begründung zu Triisobutylphosphat in TRGS 900 Ausgabe: Januar 2006 zuletzt geändert und ergänzt: März 2007).In this evaluation this study of Monsanto (1990) was also evaluated and assessed. The BAuA concluded that the observed effects, seen at the highest dose level of 5000 mg/kg diet, could not conclusively be determined as toxicological relevant. The observed effect of changes in cholesterol and the number of leucocytes are not associated with changes in white blood cell counts. Additionally the slight increase inmean corpuscular hemoglobin content and concentration did not result in other effects on red blood cells. In addition no correlation was found between the observed changes in blood parameters and the results of the clinical and histopathological assessments. The BAuA therefore, decided that the dosis of 5000 mg/kg diet can be assumed to be a marginal LOEL which will only be slightly above the actual NOAEL. According to the BauA it can thus be assumed that for the estimation of an OEL, a NAEL of 2500 mg/kg diet, which corresponds to 170 mg/kg bw for male and 210 mg/kg bw for female rats, can be used.

Supportingly, Triisobutyl phosphate was tested on 10 rats with a 0.6 % dilution in peppermint tea (BASF, 1953). No effects were observed after repeated oral intake for 51 days. Mild irritation on the kidneys was not significant. No NOAEL was identified. Triisobutyl phosphate was also tested on cats by gavage (BASF, 1953). Several effects were observed; mucous membrane irritation, salivation, vomiting, diarrhea, excitation symptoms, blood damage. No NOAEL was identified.

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. There were no significant toxic effects at doses of less than 1000 ppm (corresponding to 68.4 mg/kg bw/day in males and 84.3 mg/kg bw/day in females) upon subchronic oral exposure in rats. As a result, the substance is not classified for repeated dose toxicity under Regulation (EC) No. 1272/2008, as amended for the tenth time in Regulation (EC) No. 2017/776.