1,1'-(methylimino)dipropan-2-ol

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records

Reference

Endpoint:

one-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

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

Adequacy of study:

key study

Study period:

1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to test guidelines and in accordance with GLP

Qualifier:

according to guideline

Guideline:

other: U.S. FDA Toxicological Principles for the Safety Assessment of Direct Food Additives and Color Additives Used in Food - 21 CFR 314.50(d)(2)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

124 male and 124 female Crl:CD BR rats were acquired from Charles River Breeding Laboratories, Kingston, New York on 2/17/87. These rats were designated as the parental generation (P) rats to be mated in order to expose the first filial (F1) generation in utero prior to beginning the 90-day feeding phase. The rats were weighed the day after arrival and were 42.0-68.4 and 28.2-50.4 grams for males and females respectively. The rats were born 1/26/87 and were 22 days old upon arrival and 42 days old at study start. This strain was selected on the bases of extensive experience with that strain and its suitability with respect to longevity, hardiness, sensitivity, and low incidence of spontaneous diseases. Upon arrival at Haskell Laboratory, all rats were removed from shipping cartons and housed three per cage, sexes separate, in stainless steel, wire-mesh cages suspended above Upjohn Deotized Animal Cage Boards (DACB®) or R2 Reemay®-backed cage boards. During a quarantine period of 14 days, the rats were fed IPCRC and provided tap water ad libitum. The rats were temporarily identified with colored tail marks and cage identification, weighed at approximately three-day intervals, and observed with respect to weight gain and any gross signs of disease or injury. During the pretest period and throughout the study, the animal room was maintained on a 12-hour light/12-hour dark cycle. The target room temperature and relative humidity were 23±2°C and 50±10%, respectively. After release from quarantine by the laboratory veterinarian, 100 rats of each sex, selected on the bases of body weight gain and freedom from any clinical signs of disease or injury, were divided by computerized-stratified randomization into 4 groups of 25 male and 4 groups of 25 female rats so that there were no statistically significant differences among group body weight means within a sex. The order of rats within each group was randomized. Each group of rats within a sex was designated as either a control, low-, intermediate-, or high-concentration group. After assignment to treatment groups, each rat within a sex was identified by a number tattooed on the tail. During tattooing, but prior to administration of TIPA, one male rat in the high-concentration group was accidentally killed. This rat was replaced with a healthy rat of approximately the same weight that had not been selected during grouping. Because a rat of similar weight was used, mean group weight and differences between groups did not change. After grouping, all rats were individually housed in stainless steel, wire-mesh cages suspended above Upjohn DACB® or R2 Reemay®-backed cage boards. During the premating phase and throughout the study except during mating, male and female parental generation rats were housed on separate cage racks. Rats not selected for the study were sacrificed and discarded without pathological evaluation.

Route of administration:

oral: feed

Vehicle:

water

Details on exposure:

During the test period, parent and offspring rats in each group were fed an Irradiated Purina Certified Rodent Chow #5002 (IPCRC) diet that contained 0, 500, 2000 or 7500 ppm TIPA.Throughout the study, all rats were fed the diet of their respective treatment group and provided tap water ad libitum. Before diets were prepared, TIPA was dried with Drierite drying agent under vacuum for several days. All compound was stored in containers which were purged with nitrogen after opening.
TIPA was added to 200 ml of distilled water and mixed on a magnetic stirrer until dissolved. Dissolved TIPA was added to IPCRC and mixed in a Stephan high-speed mixer (model# VCM-80E) for 3 minutes. When this mixer was unavailable, due to a mechanical problem (6/29/87 through 8/4/87), diets were mixed in a Hobart low-speed mixer (model# M-802) for 15 minutes. Control diets, with 200 ml distilled water added, were subjected to the same mixing conditions. All diets were prepared weekly and refrigerated until used.
At the beginning of the study, samples of diet (approximately 50 g each) were collected from each concentration of diet prepared with the test material. These samples were analyzed to verify concentration, homogeneity, and stability of TIPA in the test diets. Concentration/stability samples were collected from the middle of the mixing vessel. They were either frozen the day of preparation, frozen after 24 hours at room temperature, frozen after 17 days at room temperature, or frozen after 17 days of refrigeration. Homogeneity samples were collected from the top, middle, and bottom of the mixing vessel and frozen the day of preparation. A sample of freshly prepared control diet was also collected the day of diet preparation. Diet samples were analyzed by the Molecular and Genetic Toxicology Section of Haskell Laboratory. Samples for the determination of homogeneity and stability of TIPA in the diets were also taken at the end of the P gestation phase. Stability samples were inadvertently stored for 18 days prior to freezing rather than 17 days. This is not considered to have adversely affected the outcome of the study. Homogeneity samples were taken when the diet mixer was changed to low-speed instead of high-speed (6/29/87). When the high-speed mixer was again used to prepare diets (8/17/87) another set of homogeneity samples was collected. Since this was nine days prior to the start of sacrifice, these samples were considered end-of-study samples. At the request of the sponsor to provide data on samples that were never frozen, these samples were extracted on the day of collection and analyzed the following day. Stability samples were not collected at the end of the study since the two sets of stability samples already collected from this study and the two sets of stability samples from a previous study indicated TIPA remained stable in the diet.

Details on mating procedure:

Five weeks after initiation of the P premating phase, P rats were mated to produce F1 litters. For mating, each P female rat was housed with a randomly assigned male until evidence of copulation was obtained (copulation plug) or for a maximum of seven days. If copulation was not detected within seven days, the female was housed for a second period of up to seven days with a different male which had copulated during the previous week. Upon detection of a copulation plug (designated day 0 of pregnancy), each female was returned to individual housing in its assigned cage. On day 14 of gestation, females were housed individually in polypropylene cages with bed-o'cobs cage bedding. Female rats that did not show copulation plugs by the end of the second seven-day mating period were assumed pregnant and were housed individually in the polypropylene cages at the end of this period. Female rats were observed at least twice daily for signs of delivery starting several days prior to expected parturition.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Methanol was added to each diet sample and TIPA was extracted by sonication, filtered, evaporated under nitrogen, and derivatized with Pyridine and N-Trimethylsilylimidazole (TMSI). The reaction was completed by warming the solutions to 80°C for 10 (0, 500 ppm) or 20 minutes (2000, 7500 ppm). Recovery efficiencies were determined at the 500 ppm level by adding 5 mL of a 1000 µg/mL TIPA stock solution to control diet and at the 2000 and 7500 ppm levels by adding 20.3 and 75.9 mg H-16,648, respectively, to 10.0 g control diet. Extraction and preparation of the recovery samples were performed as described above. Calibration curves were created using standarrd solutions of TIPA or TEA. Peak area ratios were calculated (TIPA to TEA) and used for quantitation by linear regression analysis. The dietary concentration of TIPA was determined by multiple injection with a Hewlett-Packard 5880A gas chromatograph.

Duration of treatment / exposure:

Twenty-five parental generation rats/sex/group were fed TIPA in diet for five weeks. After five weeks of feeding, they were mated to produce offspring which were fed diets containing TIPA for 90 days after weaning.

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
0; 500; 2,000 or 7,500 ppm TIPA
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
0; 39.7; 160; 609 mg/kg bw/day for males of the F1 generation; 0, 43.7; 182; 700 mg/kg/day for females of the F1 generation
Basis:
other: mean daily intake of TIPA over the 90-day feeding period

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale:
Dose levels for this study were selected after consultation with the FDA. Dose levels were based upon acute and subchronic studies in rats conducted with TIPA in drinking water. On an acute basis, the single dose oral LD50 of TIPA in rats was 5994 mg/kg. When rats were given 140 to 1,350 mg TIPA/kg/day in drinking water for 30 days, 1350 mg/kg/day resulted in growth reduction and decreased food consumption. A dose level of 260 mg/kg/day produced unspecified histopathologic changes in some rats. No effects were seen at 140 mg/kg/day. In a 90-day study in rats, dose levels of 770 mg TIPA/kg/day in drinking water produced kidney effects consisting of dilation of Bowman's capsule and convoluted tubules, as well as marked cloudy swelling of liver parenchyma. A level of 220 mg/kg/day produced unspecified pathological changes in some animals. A concentration of 110 mg/kg/day for 90 days revealed no microscopic changes. In the present study, the intermediate- and high-dose levels (2000 and 7500 ppm in diet) were expected to produce mean daily intakes in rats of about 200 and 700 mg/kg/day, respectively. The intermediate-concentration level was selected to be similar to one at which pathological changes were seen in some rats on a previous study (220 mg/kg/day); the high-concentration level was selected to be comparable to a level at which pathological changes were seen in all rats (770 mg/kg/day).

Positive control:

None

Parental animals: Observations and examinations:

Clinical Observations and Mortality:
Cage-site examinations to detect moribund or dead rats and abnormal behavior and appearance among rats were conducted at least once daily throughout the study. During the premating phase of the study, each rat was individually handled at each weighing and carefully examined for abnormal behavior and appearance.

Body Weights
All rats were weighed once a week during the five-week premating phase of the study.

Food Consumption, Food Efficiency, and Intake of TIPA
The amount of food consumed by each test group during each weighing interval was determined during the premating phase. From these determinations and body weight data, mean individual daily food consumption, food efficiency, and intake of TIPA were calculated.

Litter observations:

Litter counts and weights were determined collectively by sex on day 4 PP, prior to and after culling and on day 14 postpartum. 21 days after birth (weaning) individual pup weights were recorded.
Clinical signs, counts, mortality, and group body weights of F1 offspring were recorded prior to weaning. At weaning, 20 randomly selected F1 rats/sex/group were selected to continue on their respective treatment group's diet (one/sex/litter when possible). The remainder were sacrificed and discarded without pathological examination. Clinical observations, mortality, body weights, and food consumption of the F1 offspring were recorded during a 90-day feeding phase. F1 offspring were given ophthalmological examinations at the beginning and end of the 90-day feeding period. Haematology, clinical chemistry and urine analyses were conducted after approximately 45 and 90 days of feeding.

Postmortem examinations (parental animals):

None

Postmortem examinations (offspring):

At the end of the 90-day feeding period, all surviving rats were sacrificed and given a gross pathological examination. All tissues from the control and high-concentration groups were examined microscopically. Lungs, liver, kidneys, and organs with lesions in the low- and intermediate-concentration groups were also examined microscopically.

Statistics:

For the P premating, gestation, and lactation, and F1 feeding phases, body weights, body weight gains, clinical laboratory measurements, and organ weights were analyzed by a one-way analysis of variance. When the test for differences among test group means (F test) was significant, pairwise comparisons between test and control groups were made with the Dunnett's test. Incidence of clinical observations was evaluated by the Fisher's Exact test with a Bonferroni correction and the Cochran-Armitage test for trend. Homogeneity of variances of organ weights and clinical laboratory data were analyzed with the Bartlett's test (alpha = 0.005). When the results of Bartlett's test were significant (variance was not homogeneous), the Mann-Whitney U test was employed instead of Dunnett's test for comparison of means (alpha = 0.05). Comparisons of offspring numbers and weights were made with the Mann-Whitney U test and Jonckheere's test for trend. Incidences of clinical observations in offspring were evaluated by Fisher's Exact test with a Bonferroni correction and the Cochran-Armitage test for trend. Indices of reproductive performance were also evaluated by Fisher's Exact test and the Cochran-Armitage test for trend.

Reproductive indices:

Mating index, fertility index, gestation index

Offspring viability indices:

Percent pups born alive, viability index, lactation index, litter survival, average number of pups/litter

In the parent rats, there were no significant differences between groups in clinical observations, body weights, and body weight gains during the premating period or in maternal rats during gestation or lactation. No parental rats died during the premating, mating, gestation, or lactation period. Food consumption and food efficiency of parental rats were similar between groups. There were no differences in reproductive parameters, attributed to the administration of TIPA

Dose descriptor:

NOAEL

Effect level:

> 7 500 other: ppm (602 mg/kg bw/day for males; 693 mg/kg bw/day for females)

Sex:

male/female

Basis for effect level:

other: No treatment-related effects were observed up to the highest dose tested (602 mg/kg bw/day for males; 693 mg/kg bw/day for females)

There were no differences attributed to administration of TIPA in gestation length, the number of litters produced (fertility index), or any other indices of reproductive performance. No treatment-related effects on F1 pups from any TIPA-treated groups were observed in the number born, survival, body weights, or clinical signs.

In the 90-day feeding phase of the F1 rats, there were no TIPA-related changes in clinical signs, body weights, body weight gains, of food consumption. The mean daily intake of TIPA over the entire 90-day feeding period was 0, 39.7, 160, and 609 mg/kg/day. For females at the same dose group the mean daily intake ws 0, 43.7,182, and 700 mg/kg/day over the same period.

No changes in the clinical chemistry evaluations, urine analyses, ophthalmological examinations, organ weights, or pathological evaluations conducted on F1 rats were considered compound-related or biologically significant.

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

> 7 500 other: ppm (609 mg/kg bw/day for males; 700 mg/kg bw/day for females)

Sex:

male/female

Basis for effect level:

other: No treatment-related effects were observed up to the highest dose tested (609 mg/kg bw/day for males; 700 mg/kg bw/day for females)

Reproductive effects observed:

not specified

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Additional information

Currently, there is no reproductive toxicity study with1,1’-(methylimino)-dipropane-2-ol available. Nevertheless, an one generation toxicity study via the oral route of exposure (according to FDA guidelines) was carried out with tris-(2-hydroxypropyl)-amine (CAS 122-20-3) and can be used for cross reading.

 

1,1’-(methylimino)-dipropane-2-ol and tris-(2-hydroxypropyl)-amine (CAS 122-20-3) are structurally very similar low molecular weight tertiary amines, which differ only in terms of a methyl group and an isopropanol moiety respectively. They are low volatile (vapour pressure ≤ 0.015 hPa) organic compounds with similar specific gravity (1,1’-(methylimino)-dipropane-2-ol: 147.22 g/mol and tris-(2-hydroxypropyl)-amine: 191.27 g/mol) and log Pow values between -0.03 for 1,1’-(methylimino)-dipropane-2-ol and -0.02 for tris-(2-hydroxypropyl)-amine. Moreover, the comparison of the available toxicity data for both compounds indicates a similar toxicological profile: the substances are showing low acute toxicity by the oral route (i.e. oral LD50 values for 1,1’-(methylimino)-dipropane-2-ol of 2150 mg/kg bw and beyond 5000 mg/kg bw for tris-(2-hydroxypropyl)-amine. Tris-(2-hydroxypropyl)-amine is irritating to the eyes, whereas 1,1’-(methylimino)-dipropane-2-ol shows corrosive properties. For a detailed read across justification see also attached assessment reports (Reporting Format for the analogue approach of 1,1’-(methylimino)-dipropane-2-ol– with comparison to tris-(2-hydroxypropyl)-amine).

In an one-generation study according to FDA guidelines, Sprague-Dawley rats (25/sex/dose) were administered tris-(2-hydroxypropyl)-amine via the diet at 0, 500, 2000 or 7500 ppm (approximately 0, 39.7, 160 or 609 mg/kg bw in males or 0, 43.7, 182 or 700 mg/kg bw in females) for 5 weeks prior to mating as well as during mating, gestation and lactation (DuPont, 1988). Offspring (20/sex/dose) were also administered the same doses for 90 days after weaning and ophthalmological, clinical chemistry, haematology and urinalysis examinations were conducted. Histopathological examination was conducted on controls and high-dose animals for all organs and on lungs, liver, kidneys and organs with lesions at the low and intermediate doses. No adverse clinical, histological, or reproductive effects (mating index, fertility index, gestation index, gestation length, percent pups born alive, viability index, lactation index, litter survival, average number of pups/litter, litter size) were noted. The NOAEL was reported to be 609 mg/kg bw/day for males and 700 mg/kg bw/day for females, the highest doses tested. In addition, no effects on the reproductive organs of male or female dogs were identified in the sub-chronic repeated dose study (DuPont, 1988).

Short description of key information:
There is an one generation toxicity study with a structural analogue of N-Methyldiisopropanolamine, tris-(2-hydroxypropyl)-amine available:
Reproductive toxicity was investigated in an one-generation study (according to FDA guidelines) in which rats were administered tris-(2-hydroxypropyl)-amine in the diet for 5 weeks prior to mating, during mating, gestation, lactation, and for 90 days post-weaning (offspring). The NOAEL for reproductive effects was reported 609 mg/kg bw/day for males and 700 mg/kg bw/day for females, the highest dose tested.

Justification for selection of Effect on fertility via oral route:
1,1’-(methylimino)-dipropane-2-ol and tris-(2-hydroxypropyl)-amine (CAS 122-20-3) are structurally very similar low molecular weight tertiary amines, which differ only in terms of a methyl group and an isopropanol moiety respectively. They are low volatile (vapour pressure ≤ 0.015 hPa) organic compounds with similar specific gravity (1,1’-(methylimino)-dipropane-2-ol: 147.22 g/mol and tris-(2-hydroxypropyl)-amine: 191.27 g/mol) and log Pow values between -0.03 for 1,1’-(methylimino)-dipropane-2-ol and -0.02 for tris-(2-hydroxypropyl)-amine. Moreover, the comparison of the available toxicity data for both compounds indicates a similar toxicological profile: the substances are showing low acute toxicity by the oral route (i.e. oral LD50 values for 1,1’-(methylimino)-dipropane-2-ol of 2150 mg/kg bw and beyond 5000 mg/kg bw for tris-(2-hydroxypropyl)-amine. Tris-(2-hydroxypropyl)-amine is irritating to the eyes, whereas 1,1’-(methylimino)-dipropane-2-ol shows corrosive properties. The chemical difference between those two structures apparently do not affect the anticipated toxicity. Therefore, tris-(2-hydroxypropyl)-amine is regarded as appropriate for read across.

Effects on developmental toxicity

Description of key information

There is a developmental toxicity study with a structural analogue of N-Methyldiisopropanolamine, tris-(2-hydroxypropyl)-amine available: 
In an OECD guideline 414 developmental toxicity study, pregnant female rats were administered  tris-(2-hydroxypropyl)-amine via oral gavage on gestation days 6 to 15. The maternal and developmental NOAELs were 400 and 1000 mg/kg bw/day, respectively.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

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

Adequacy of study:

key study

Study period:

27. Jan 1994 - 21. Feb 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study (OECD 414), GLP compliant.

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: THOMAE, Biberach an der Riss, FRG
- Age at study initiation: 77-89 days
- Weight at study initiation: 242 g (mean)
- Housing: singly in type DK III stainless steel wire mesh cage.
- Diet: ground Kliba 343 feed, Klingenthalmuehle AG, Kaiseraugst, Switzerland, ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 30-70%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: doubly distilled water

Details on exposure:

Doses of 0, 100, 400 and 1000 mg/kg bw/day were administered in a volume of 10 ml/kg, at a concentration of 0, 1000, 4000 and 10000 mg/100ml, respectively.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Test substance: purity and stability were analyzed by gas chromatography (GC); and homogeneity was proven visually.
Test solutions: analysis of stability (for 3 hrs) in double distilled water was carried out in a range-finding study. Concentrations were analyzed twice during the study by GC. Test solutions were freshly prepared on the day of dosing.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: overnight
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

on day 6 through day 15 post coitum (p.c.)
(Sacrifice on day 20 p.c.)

Frequency of treatment:

once a day during the period of major organogenesis (day 6 to day 15 p.c.)

Duration of test:

20 days

Remarks:

Doses / Concentrations:
0; 100; 400; 1000 mg/kg bw/d
Basis:
nominal conc.

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: once a day and more often when clinical signs of toxicity were elicited. Mortality was check twice a day on workdays and once a day during weekends and public holidays.

BODY WEIGHT and FOOD CONSUMPTION: Yes
- Time schedule for examinations: days 0 (only bw), 1, 3, 6, 8, 10, 13, 15, 17, 20 p.c.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: uterus and ovaries after gross pathology

OTHER: The correct body weight gain was calculated after terminal sacrifice.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: furthermore, calculations of conception rate and pre- and postimplantation losses were carried out

Fetal examinations:

- External examinations: Yes: all per litter: fetus was weighed, sexed, examined macroscopically for external findings, and viability, condition of the placentae, umbilical cords, fetal membranes and fluids were examined.
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: No

Statistics:

The data were evaluated statistically using the computer systems of the Department of Toxicology of BASF AG. The Dunnett-test was used for a simultaneous comparison of several dose groups with the control. The hypothesis of equal means was tested. This test was performed two-sided and was used for the statistical evaluation of the following parameters: food consumption, body weight, body weight change, corrected body weight gain (net maternal body weight change), weight of the uterus before it was opened, number of corpora lutea, number of implantations, number of resorptions and number of live fetuses, proportion of preimplantation loss, postimplantation loss, resorptions and live fetuses in each litter, litter mean fetal body weight and litter mean placental weight. Fisher's Exact Test was used for a pairwise comparison of each dose group with the control for the hypothesis of equal proportions. This test was performed one-sided and was used for female mortality, females pregnant at terminal sacrifice and the number of litters with fetal findings. The Wilcoxon-Test was used for a comparison of each dose group with the control for the hypothesis of equal medians. This test was performed one-sided and was used for the proportion of fetuses with malformations, variations, retardations and/or unclassified observations in each litter. If the results of these tests were significant, labels (* for p< 0.05, ** for p< 0.01) were printed in the summary tables.

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
In the 1000 mg/kg group statistically significantly decreased food consumption at the beginning of the treatment period (days 6-10 p.c.; about 13% (days 6 to 8 p.c.) or about 16% (days 8 to 10 p.c.) lower than the values of the concurrent control group. There were no statistically significant differences between the controls and the substance-treated dams concerning mean body weights. At the beginning of the treatment period (days 6-8 p.c.), however, the dams of the highest dose group (1,000 mg/kg body weight/day) showed a statistically significantly reduced body weight gain (only about 36% of the weight gain of the concurrent control group; see table in remarks on results). The corrected body weight gain (terminal body weight on day 20 p.c. minus weight of the uterus before it was opened minus body weight on day 6 p.c.) was statistically significantly lower in the high dose group (about 87% of the value of the concurrent control group), which is related to the test substance administration (see table in remarks on results). There were no substance-related and/or biologically relevant differences between the groups in conception rate, in the mean number of corpora lutea and implantation sites or in the values calculated for the pre- and the postimplantation losses, the number of resorptions and viable fetuses. The differences evident are considered to be incidental and within the normal range of deviations for animals of this strain and age.

Dose descriptor:

NOAEL

Effect level:

400 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The few statistically significant differences on embryo-/fetotoxicity, which occurred were exclusively related to fetal skeletal variations and retardations. These findings consisted of: an increased rate of affected fetuses/litter and an increased litter incidence with shortened 13th rib(s) at 100, 400 and 1,000 mg/kg bw/day, respectively; a consequently increased rate of low and intermediate dose fetuses/litter with total skeletal variations; an increased litter incidence of incompletely ossified or smaller sternebra(e) in the 400 mg/kg body weight group. These findings are considered to be spontaneous in nature because no dose-response relationship is given and/or the respective values are fully in the historical control range.

Dose descriptor:

NOAEL

Effect level:

>= 1 000 mg/kg bw/day

Basis for effect level:

other: teratogenicity

Abnormalities:

not specified

Developmental effects observed:

not specified

Mean maternal body weight change during gestation (grams):

	0 mg/kg bw/d(n = 25)	100 mg/kg bw/d(n = 24)	400 mg/kg bw/d(n = 25)	1000 mg/kg bw/d(n = 23)
Days 0 - 1	4.3±3.76	3.7±3.60	4.3±3.41	4.3±2.89
Days 1 - 3	11.7±3.56	11.9±3.41	11.7±3.77	11.8±2.95
Days 3 - 6	13.0±4.56	12.1±4.40	13.1±4.37	12.5±3.39
Days 6 - 8	7.5±3.90	7.4±4.21	5.0±4.26	2.7±3.93**
Days 8 - 10	9.9±4.59	9.4±5.15	11.4±4.43	8.0±3.72
Days 10 - 13	17.5±3.57	17.1±4.92	19.1±5.42	19.0±4.98
Days 13 - 15	11.7±4.51	11.9±4.15	12.5±4.36	13.7±4.62
Days 15 - 17	25.4±6.47	25.8±5.23	25.3±4.38	26.6±3.60
Days 17 - 20	50.3±10.57	49.2±6.64	51.8±7.58	52.6±5.56

**: p ≤ 0.01; Dunnett-test.

Mean gravid uterine Weights and net maternal body weight change (grams):

	0 mg/kg bw/d(n = 25)	100 mg/kg bw/d(n = 24)	400 mg/kg bw/d(n = 25)	1000 mg/kg bw/d(n = 23)
Gravid uterus	78.3±19.22	80.3±10.49	82.5±13.18	84.4±10.16
Carcass	317.7±22.09	310.8±20.66	314.3±22.22	306.2±13.17
Net weight change from day 6	44.1±8.54	40.4±7.52	42.6±7.06	38.2±6.72*

*: p ≤ 0.05; Dunnett-test.

Under the conditions of this full-scale prenatal toxicity study, the administration of Triisopropanolamine to pregnant female Wistar rats during organogenesis elicited overt signs of maternal toxicity at 1000 mg/kg body weight/day, while 100 or 400 mg/kg body weight/day were tolerated by the dams without any substance-induced findings. The gestational parameters were not influenced by the test substance administration in any of the three test groups.

No signs of embryo-/fetotoxicity, especially no substance-induced indications of teratogenicity were noted up to and including the dose of 1,000 mg/kg body weight/day.

Therefore, the no observed adverse effect level (NOAEL) for the dams in this full-scale prenatal toxicity study is 400 mg/kg body weight/day, while it is 1000 mg/kg body weight/day for the fetal organism.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Additional information

Currently, there is no prenatal developmental toxicity study with1,1’-(methylimino)-dipropane-2-ol available. Nevertheless, a developmental toxicity study via the oral route of exposure (OECD TG 414) was carried out with tris-(2-hydroxypropyl)-amine (CAS 122-20-3) and can be used for cross reading.

1,1’-(methylimino)-dipropane-2-ol and tris-(2-hydroxypropyl)-amine (CAS 122-20-3) are structurally very similar low molecular weight tertiary amines, which differ only in terms of a methyl group and an isopropanol moiety respectively. They are low volatile (vapour pressure ≤ 0.015 hPa) organic compounds with similar specific gravity (1,1’-(methylimino)-dipropane-2-ol: 147.22 g/mol and tris-(2-hydroxypropyl)-amine: 191.27 g/mol) and log Pow values between -0.03 for 1,1’-(methylimino)-dipropane-2-ol and -0.02 for tris-(2-hydroxypropyl)-amine. Moreover, the comparison of the available toxicity data for both compounds indicates a similar toxicological profile: the substances are showing low acute toxicity by the oral route (i.e. oral LD50 values for 1,1’-(methylimino)-dipropane-2-ol of 2150 mg/kg bw and beyond 5000 mg/kg bw for tris-(2-hydroxypropyl)-amine. Tris-(2-hydroxypropyl)-amine is irritating to the eyes, whereas 1,1’-(methylimino)-dipropane-2-ol shows more potent and corrosive properties. For a detailed read across justification see also attached assessment reports (Reporting Format for the analogue approach of 1,1’-(methylimino)-dipropane-2-ol– with comparison to tris-(2-hydroxypropyl)-amine).

Twenty-five female Wistar rats were administered tris-(2-hydroxypropyl)-amine at 0, 100, 400 or 1000 mg/kg bw/day via oral gavage on gestation days 6 to 15 in an OECD guideline 414 study (BASF AG, 1995b). Food consumption, body weights and clinical signs of the dams were recorded. At necropsy on day 20 post coitum, dams were investigated for gross pathology (including weight determination of the unopened uterus), fetuses were removed and sexed, weighed and further investigated for any external, soft tissue and/or skeletal findings. In the highest dose group, decreased food consumption and reduced body weight gain was observed in the dams. No further treatment-related effects were observed in the dams or in the fetuses. Thus, NOAELs of 400 mg/kg bw/day for maternal toxicity and 1000 mg/kg bw/day (the highest dose tested) for teratogenicity were established.

Justification for selection of Effect on developmental toxicity: via oral route:
1,1’-(methylimino)-dipropane-2-ol and tris-(2-hydroxypropyl)-amine (CAS 122-20-3) are structurally very similar low molecular weight tertiary amines, which differ only in terms of a methyl group and an isopropanol moiety respectively. They are low volatile (vapour pressure ≤ 0.015 hPa) organic compounds with similar specific gravity (1,1’-(methylimino)-dipropane-2-ol: 147.22 g/mol and tris-(2-hydroxypropyl)-amine: 191.27 g/mol) and log Pow values between -0.03 for 1,1’-(methylimino)-dipropane-2-ol and -0.02 for tris-(2-hydroxypropyl)-amine. Moreover, the comparison of the available toxicity data for both compounds indicates a similar toxicological profile: the substances are showing low acute toxicity by the oral route (i.e. oral LD50 values for 1,1’-(methylimino)-dipropane-2-ol of 2150 mg/kg bw and beyond 5000 mg/kg bw for tris-(2-hydroxypropyl)-amine. Tris-(2-hydroxypropyl)-amine is irritating to the eyes, whereas 1,1’-(methylimino)-dipropane-2-ol shows corrosive properties. The chemical difference between those two structures apparently do not affect the anticipated toxicity. Therefore, tris-(2-hydroxypropyl)-amine is regarded as appropriate for read across.

Justification for classification or non-classification

Based on the available data,1,1’-(methylimino)-dipropane-2-ol does not need to be classified according to Directive 67/548/EEC and according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.