2,2-dimethylpropane-1,3-diol

Toxicity to reproduction

Administrative data

Endpoint:

one-generation reproductive toxicity

Remarks:

based on generations indicated in Effect levels (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was conducted according to OECD Guideline 422. GLP standards were fulfilled. Since a detailed report in English is not available (only in Japanese with tables in English) not all details of this study are documented but the data base is sufficient for evaluation. Acceptable restrictions: no data were given on historical control range for hematology and clinical chemistry of this laboratory; hematology & clinical chemistry only in males; no details about test animals, application volume and concentration, mating procedure, analysis of dose, and stability in vehicle. Data presented in the MHW SIDS dossier are partly contradictory to the original data in Biosafety Research 1993, e.g. organ weights in females.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1993

Reference 2

Reference Type:

publication

Title:

JETOC Information sheet 2,2-Dimethyl-l,3-propanediol

Author:

JETOC

Year:

1995

Bibliographic source:

JAPAN CHEMICAL INDUSTRY ECOLOGY-TOXICOLOGY & INFORMATION CENTER, JETOC No.18, April, 1995, Tokyo, Japan

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

(hematology and clinical chemistry only in males)

GLP compliance:

yes

Remarks:

Biosafety Research Center; Foods, Drugs and Pesticides, An-pyo Center, Japan

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,2-dimethylpropane-1,3-diol

EC Number:

204-781-0

EC Name:

2,2-dimethylpropane-1,3-diol

Cas Number:

126-30-7

Molecular formula:

C5H12O2

IUPAC Name:

2,2-dimethylpropane-1,3-diol

Details on test material:

purity 99,15%
Main impurities: neopentyl glycol formic acid ester and neopentyl glycol isolactic acid ester (according to SIDS dossier)
No further data

Test animals

Species:

rat

Strain:

other: Sprague-Dawley (slc:SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

Housing condition
Temperature: 22-24°C
Rel. air humidity: 50-60%
Photoperiod: 12h/12h (150-300 lux)

No further details

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

No details available, especially no data on concentration in vehicle (distilled water) and application volume.

Details on mating procedure:

12 pairs mated at each dose level; max. 6 conceiving days.
No further details.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Exposure period
Males: 45 days; females: from 14 days before mating to day 3 of lactation
Premating exposure period (males): not clearly stated but presumably ca. 6 weeks
Premating exposure period (females): 14 days
Duration of test: terminal kill for males at day 46 and females at day 4 of lactation

Frequency of treatment:

once daily

Details on study schedule:

no further details

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 100, 300, 1000 mg/kg bw/d
Basis:
no data
but presumably actual ingested dose; 1000 mg/kg bw/day is the recommended limit dose according to OECD422

No. of animals per sex per dose:

12 males and 12 females per dose

Control animals:

yes, concurrent vehicle

Details on study design:

No further details

Positive control:

No

Examinations

Parental animals: Observations and examinations:

DETAILED CLINICAL OBSERVATIONS: Yes (no details)

BODY WEIGHT: Yes
- Time schedule for examinations: Males day 0 and then once weekly during exposure period; females day 0, 7, 14 in premating period, day 0, 7, 14, 21 during gestation; day 1 and 4 in lactation period.

FOOD CONSUMPTION: Yes
No details

WATER CONSUMPTION: No data

HEMATOLOGY (only males)
all parameters recommended in OECD Guideline 422; no details about sampling.

CLINICAL CHEMISTRY (only males)
all parameters recommended in OECD 422 except sodium & cholesterol; no details about sampling.

Oestrous cyclicity (parental animals):

yes, data recorded in all dose groups (no details).

Sperm parameters (parental animals):

No data available (not mandatory according to OECD422)

Litter observations:

Live pups at birth and at day 4; Sex ratio; litter & pup weight at birth and at day 4; loss of offsprings; abnormal pups

Postmortem examinations (parental animals):

Organ weights (absolute and relative) determined at termination. Not all organs recommended in OECD422 were presented in the result section (no details given in methods but presumably no effects detected on organ weights and therefor not included in the result section; presumably the examinations correspond to the Guideline).

Necropsy and histopathology performed. Not all organs recommended in OECD422 were presented in the result section (no details given in methods but presumably no effects detected in pathological examinations and examinations correspond to the Guideline).

Postmortem examinations (offspring):

Termination at lactation day 4; external examinations.

Statistics:

No details about methods but statistical significance was calculated; limit of significance p<0.05.
Mean +- standard deviation (SD) was given.

Reproductive indices:

Copulation index
Fertility index
Gestation index
Implantation index
Delivery index

Offspring viability indices:

Birth index
Viability index on day 4

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Other effects:

effects observed, treatment-related

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

effects observed, treatment-related

Reproductive function: sperm measures:

not specified

Reproductive performance:

no effects observed

Details on results (P0)

The relevant results are presented in the Tables below.
-Clinical signs & mortality
No treatment-related clinical signs and no mortality was found in any group.

- Body weight and food consumption
of males and females in the treatment groups did not reveal any differences when compared to the control group.

- Hematology
No effects were detected in hematology of male rats.

- Clinical chemistry
revealed increased levels of total protein, total bilirubin and albumin among male rats receiving 300 and 1000 mg/kg bw/day and a decrease in glucose in male rats receiving 1000 mg/kg (no clinical chemistry in females). Other effects in clinical chemistry (see Table) were not considered by the authors to be of toxicological relevance (no dose dependency or within the standard deviation of the concurrent control).

- Organ weights
Absolute and relative weights of the liver of male rats receiving 300 and 1000 mg/kg bw/day were elevated. Absolute and relative kidney weights were elevated in male rats receiving 1000 mg/kg bw/day (see Table below). No effects were found in females (including liver and kidney).
Weights of reproductive organs were not affected in males (epididymides, testis) and females (ovaries).

- Necropsy & Histopathology
No effects detected in females.
Liver: In examinations of the liver hypertrophy was found in 2/12 male rats at 1000 mg/kg bw/day. However, histopathological examination revealed no definite associated lesion of the liver.
Kidney: Histopathological examination revealed increases in the amounts of protein casts, hyaline droplets and an increase in the severity in basophilic alteration of the renal tubular epithelium in male rats receiving 1000 mg/kg bw/day; data are presented in the Table below.

REPRODUCTIVE PERFORMANCE
Copulation was not altered by the treatment (see copulation index in the Table below); the number of pregnant rats after successful copulation was not reduced by the treatment (see fertility index); the estrus cycle was slightly but significantly (p<0.05) prolonged at 1000 mg/kg bw/day, however, the biological relevance is questionable (see also standard deviation corresponding to individual variance). Mean number of corpora lutea were not changed by the treatment (see Table below; Implantation index).
The following parameters were also not altered: Delivery index, Birth index, and Viability index post natal day 4 (see Table below).

Effect levels (P0)

1

Dose descriptor:

NOEL

Effect level:

100 mg/kg bw/day

Sex:

male

Basis for effect level:

other: repeated dose toxicity; authors evaluation in JETOC1995 without explanations (NOAEL not given)

2

Dose descriptor:

NOAEL

Effect level:

300 mg/kg bw/day

Sex:

male

Basis for effect level:

other: based on effects in the kidney of male rats at 1000 mg/kg bw/day.

3

Dose descriptor:

NOEL

Effect level:

1 000 mg/kg bw/day

Sex:

female

Basis for effect level:

other: repeated dose toxicity; highest dose level tested

4

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: reproductive performance

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Histopathological findings:

not specified

Details on results (F1)

Findings of delivery
No effects on duration of gestation, number of total implants, total born pups (live pups), sex ratio, loss of offspring, live pups at day 4, pup weight, and litter weight. External examination revealed no increase in abnormal pups to be caused by test substance (2 pups with trauma in the low dose group).
Results are presented in the Table below.

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

1 000 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: developmental toxicity

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

Blood chemistry in males treated with neopentyl glycol
n=12 in each group

Parameter	Dose in mg/kg bw/day
	0	100	300	1000
Glucose (mg/dl)	152+-7	154+-17	164+-26	140+-10**
Total bilirubin (mg/dl)	0.25+-0.02	0.26+-0.02	0.28+-0.02*	0.32+-0.04**
Blood urea nitrogen (mg/dl)	15.5+-2.4	17.7+-4.4	18.2+-3.0	18.8+-2.6
Creatinine (mg/dl)	0.64+-0.04	0.66+-0.08	0.69+-0.09	0.68+-0.06
Total protein (g/dl)	6.02+-0.18	6.07+-0.11	6.29+-0.16**	6.42+-0.19**
Albumin (g/dl)	3.25+-0.12	3.31+-0.09	3.46+-0.16**	3.52+-0.14**
Potassium (mmol/l)	4.87+-0.23	4.52+-0.41*	4.91+-0.38	4.72+-0.24
Chloride (mmol/l)	105.5+-1.3	106.8+-1.8	106.5+-1.7	105.2+-1.2
Calcium (mmol/l)	9.34+-0.31	9.64+-0.24*	9.81+-0.42**	9.67+-0.27*
Inorganic phosphate (mg/dl)	5.37+-0.67	5.75+-0.52	6.43+-0.96**	5.68+-0.48
GOT (U/l)	49+-10	38+-4**	42+-10*	43+-8
GPT (U/l)	24+-5	21+-5	23+-3	20+-2
Gamma-GT (U/l)	0.5+-0.4	1.4+-0.5**	0.3+-0.5	0.5+-0.4
mean +-SD; *: p<0.05; **: p<0.01

x

x

x

Organ weights in males treated with neopentyl glycol
n=12 in each group

Parameter	Dose in mg/kg bw/day
	0	100	300	1000
Body weight in g	391+-23	395+-23	399+-27	392+-30
Thymus (absolute in mg)	303+-70	333+-36	286+-57	313+-82
Liver (absolute in g)	11.2+-1.15	11.5+-0.96	12.5+-1.18*	13.1+-1.43**
Kidney (absolute in g)	2.61+-0.18	2.70+-0.16	2.83+-0.24	2.94+-0.33*
Testes (absolute in g)	3.41+-0.16	3.45+-0.18	3.42+-0.15	3.47+-0.22
Epididymides (absolute in g)	1.18+-0.08	1.25+-0.10	1.19+-0.10	1.23+-0.14
Liver (relative)	2.86+-0.16	2.91+-0.22	3.14+-0.15**	3.33+-0.17**
Kidney (relative)	0.67+-0.037	0.68+-0.046	0.71+-0.049	0.75+-0.052**
mean +-SD; *: p<0.05; **: p<0.01

x

x

x

Histopathological findings in the kidney of males treated with neopentyl glycol
Number of rats with slight (1), moderate (2) or severe (3) effects

Findings	Dose in mg/kg bw/day
	0 (n=12)	100 (n=10)	300 (n=12)	1000 (n=11)
Basophilic changes	10 (1)	9 (1), 1 (2)	11 (1)	7 (1), 4 (2)
Deposits of calcium	3 (1)	1 (1)	1 (1)	2 (1)
Eosinophilic body	12 (1)	10 (1)	12 (1)	11 (1)
Hyaline droplets	0	1 (1)	0	4 (1)
Protein casts	1 (1)	1 (1)	2 (1)	5 (1)
Lymphocytic infiltration	0	1 (1)	1 (1)	0
Fibrosis	0	1 (1)	0	0

x

x

x

Reproductive performance in rats treated with neopentyl glycol and
developmental effects in offsprings

Parameter	Dose in mg/kg bw/day
	0	100	300	1000
No. of pairs mates	12	12	12	12
Estrus cycle (days)	4.0+-0.1	4.0+-0.1	4.1+-0.3	4.3+-0.4*
No. of pairs copulated	12	11	12	12
Copulation index in %	100	92	100	100
No. of pregnant rats	12	10	12	11
Gestation index in %	92	100	100	100
No. of dams delivered live pups	11	10	12	11
Duration of gestation (days)	21.1+-0.3	21.3+-0.5	21.3+-0.5	21.4+-0.5
Fertility index in %	100	91	100	92
No. of corpora lutea per litter	15.5+-1.0	15.7+-1.2	16.1+-1.7	14.9+-1.8
No. of implants per dam	14.8+-1.2	15.2+-1.3	15.3+-1.2	13.9+-2.7
Implantation index in %	96+-4.6	97+-3.4	96+-6.2	93+-14.0
No. of live pups born per litter	13.7+-1.2	14.1+-1.6	14.0+-2.8	12.8+-2.2
Delivery index in %	93+-5.1	93+-7.1	91+-15.6	93+-5.3
Sex ratio (m/f)	0.80	1.17	0.98	0.88
No. of dead pups born per litter	0.1+-0.3	0	0	0
Birth index in %	93+-6.1	93+-7.1	91+-15.6	93+-5.3
No. of live pups per litter at pn day 3 #	13.3	13.7	13.8	12.5
Viability index pn day 4 in % (males)	97+-6.8	100	98+-5.3	99+-3.8
Viability index pn day 4 in % (females)	96+-7.8	95+-8.1	99+-2.4	97+-6.3
Litter weight at birth #	79.5	79.2	78.5	74.7
Litter weight at pn day 3 #	104	103	102	98
Pup weight at birth #	5.8	5.5	5.7	5.8
Pup weight at pn day 3 #	7.9	7.5	7.7	7.9
Dams with pups showing abnormalities (except trauma)	0/11	0/10	0/12	0/11
Dams with no pn loss of offspring	7	7	9	8
Dams with pn loss of offspring	4	3	3	3
Mean +- SD; pn: post natal; #: mean given but not SD; *: p<0.05

Copulation index: (no. of dams with successful copulation/no. of rats mated) x 100

Fertility index: (no. of pregnant rats/ no. of rats with successful copulation) x 100

Gestation index: (no. of dams with live pups/ no. of pregnant dams) x 100

Implantation index: (no. of total implants/ no. total corpora lutea) x 100

Delivery index: (no. of pups born/ no. of implants) x 100

Birth index: (no. live pups born/number of implants) x 100

Viability index pn day 4: (no. of live pups at pn day 4/ no. of live pups born) x 100

Applicant's summary and conclusion

Conclusions:

Reproductive performance of the parent generation and development of the F1 generation were not affected after oral application of dose levels up to 1000 mg/kg bw/day. Concerning repeated dose toxicity the high dose resulted in no toxic effects in females but in males; the NOAEL is 300 mg/kg bw/day.

Executive summary:

The study was conducted according to OECD Guideline 422. GLP standards were fulfilled. Since a detailed report in English is not available (only in Japanese with tables in English) not all details of this study are documented but the data base is sufficient for evaluation. Acceptable restrictions: no data were given on historical control range for hematology and clinical chemistry of this laboratory; hematology & clinical chemistry only in males; no details about test animals, application volume and concentration, mating procedure, analysis of dose, and stability in vehicle.

Twelve male and 12 female Sprague-Dawley rats per dose were gavaged with 0, 100, 300, or 1000 mg/kg bw/day. The exposure period for males was 45 days; females were treated from day 14 before mating to day 3 of lactation. The premating exposure period for males was not clearly stated but presumably ca. 6 weeks. There was no post exposure observation period. Body weight and food consumption was measured in all groups. Estrous cyclicity was determined before mating. Hematology and clinical chemistry was performed in males. The following litter observations were recorded: live pups at birth and at day 4 (termination); sex ratio; litter & pup weight at birth and at day 4; loss of offsprings; abnormal pups. At termination organ weights (absolute and relative) were determined and necropsy and histopathology performed. The following reproductive/developmental indices were measured: copulation index, fertility index, gestation index, implantation index, delivery index, birth index, and viability index on day 4.

The reproductive performance and the development of the offspring were not affected by oral application of dose levels up to 1000 mg/kg bw/day. Concerning the repeated dose toxicity in females of the parent generation no effects were detected. At 100 mg/kg bw/day no effects were recorded in males. At >= 300 mg/kg bw/day a dose dependent increases in the levels of total protein, total bilirubin and albumin in clinical chemistry was measured and the absolute and relative liver weight was increased in males. At a dose level of 1000 mg/kg bw/day a reduced blood glucose value was observed and absolute and relative kidney weight was increased in males; histopathology of high dose males revealed hypertrophy of the liver in 2/12 males, increased severity in basophilic alteration of the renal tubular epithelium accompanied by an increased incidence in hyaline droplets and protein casts.

The toxicological relevance of altered parameters in clinical chemistry is questionable. No comparison is available with historical control ranges of the same laboratory. These data are not used for final evaluation. The increase in liver weight was not found to be parallel to any histpathologically detected liver lesion and furthermore no clear indication of such a liver lesion was found in other parameters investigated. Therefore, the increase in liver weight at mid and high dose level and liver hypertrophy at the high dose is considered to be an adaption to the increased metabolism of neopentyl glycol and not an adverse effect per se. However, the increased kidney weight at 1000 mg/kg bw/day accompanied by hyaline droplets and protein casts in the eliminating renal lumen plus alterations of the renal tubular epithelium (increased basophilicity) are suggested to be adverse in nature.

Conclusion: Reproductive performance of the parent generation and development of the F1 generation were not affected after oral application of dose levels up to 1000 mg/kg bw/day. Concerning repeated dose toxicity the high dose resulted in no toxic effects in females but in males; the NOAEL is 300 mg/kg bw/day.