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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1989
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study according to OECD guideline 408
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1989
Report Date:
1989

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Principles of method if other than guideline:
n/a
GLP compliance:
yes
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Identity: Dowanol-DPnB (n-butoxypropoxypropanol or
dipropylene glycol normal-butyl ether).
CAS # 29911-28-2
Batch No.: O2
Product ID: E-3125
Purity: see below
Supplied as: Not reported.
Appearance: Colorless liquid.
Administered as: Mixed with microgranulated feed and
pelleted.
Vapor pressure: Not specified.
Specific Gravity: Not specified.
Solubility: Not specified.
Stability: Stable at room temperature until April
1989.

Dipropylene glycol n-butyl ether isomers: 99.2 %
Dipropylene glycol and water combined: 0.8 %

Dipropylene glycol n-butyl ether (DPnB) is a mixture of 4
possible isomers with the major isomers being
1-(1-n-butoxy-2-propoxy)-2-propanol and
2-(1-n-butoxy-2-propoxy)-1-propanol.

Test animals

Species:
rat
Strain:
other: SSprague-Dawley, outbred SPF - Stock KFM: SPRD
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: KPF - SPRD
- Diet: ad libitum
- Water: ad libitum
- Age at study initiation: 10 weeks
- Weight at study initiation: 222-265 g for males, 172-207 for females
- Acclimation period: 10 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 + or - 3
- Humidity (%): 40-70
- Photoperiod (hrs dark / hrs light): 12/12
- Air change: 10-15 change/hour

For details, pls. see table 1 below

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Four groups of Sprague-Dawley rats (20/sex/dose level) received dipropylene glycol n-butyl ether (DPnB) in their feed at concentrations equivalent to target doses of 0, 200, 450, or 1000 mg/kg-day for 13 weeks.  Five additional rats per sex were added to each group.  These additional rats received DPnB in their feed for only four weeks and then were sacrificed in order to assess DPnB toxicity at this interim period.  
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples were sent to analytical laboratory of RCC for analysis of homogenicity and concentration.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
Daily
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 200, 450, or 1000 mg/kg-day
Basis:
nominal in diet
No. of animals per sex per dose:
20/sex/dose
Control animals:
yes
Details on study design:
Four groups of Sprague-Dawley rats (20/sex/dose level) received dipropylene glycol n-butyl ether (DPnB) in their feed at concentrations equivalent to target doses of 0, 200, 450, or 1000 mg/kg-day for 13 weeks.  Five additional rats per sex were added to each group.  These additional rats received DPnB in their feed for only four weeks and then were sacrificed in order to assess DPnB toxicity at this interim period.  

Nominal doses and weekly ranges of doses are reported in the table below.  Concentrations of DPnB in feed were adjusted on a weekly basis, based on food consumption patterns, to achieve the desired dose.  For males, concentrations of DPnB in feed ranged from: 1) 2200-3400 ppm for the 200 mg/kg-d group, 2) 4950-7200 ppm for the 450 mg/kg-d group, and 3) 11000-16000 ppm for the 1000 mg/kg-d group.  For females, concentrations of DPnB in feed ranged from: 1) 2150-2700 ppm for the 200 mg/kg-d group, 2) 4840-6000 ppm for the 450 mg/kg-d group, and 3) 10750-13200 ppm for the 1000 mg/kg-d group.

Study design: see table 2 below
Positive control:
none

Examinations

Observations and examinations performed and frequency:
Rats were observed for mortality twice daily and for clinical signs of toxicity once per day.  Once weekly, animals were given a more detailed clinical examination with palpation for masses.  Body weights, water, and food consumption were monitored weekly.  Ophthalmological examinations were conducted prior to treatment and at sacrifice (interim animals included).  Hematology, clinical chemistry, and urinalysis evaluations were conducted at 4 and 13 weeks.  
Sacrifice and pathology:
At sacrifice, all control and high dose animals were subjected to complete necropsy and histopathological evaluations.  Gross lesions were recorded at necropsy.  Selected organs were weighed and over 40 tissues were collected from all animals and fixed for histopathological evaluation.  Only tissues from control and high-dose animals were evaluated histopathologically.
Other examinations:
none

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
Absolute and relative liver weights were increased in high dose males.   In females at the high dose level, absolute and relative kidney weights were increased with no accompanying histopathology.  Slight alterations in clinical chemistries, electrolytes, and hematology also were noted in both sexes at the high dose level.  No changes in any other monitored parameters were noted at any dose level.  The NOAEL for DPnB is 450 mg/kg-day and the LOAEL is 1000 mg/kg-day (for organ weight changes).

Morbidity/Mortality:  All rats survived treatment with the test compound.

Clinical signs:  No treatment-related signs reported.

Food Consumption:  A slight increase in relative food consumption (to body weight) but not absolute food consumption was noted in high dose males.

Water Consumption:  No effect on water consumption was noted.

Body weights:  Body weights in high dose males were slightly decreased during the first three weeks of treatment.  Although not statistically significant thereafter, this trend continued in the high dose males throughout the study. Body weights were unaffected in high dose females or in either sex from lower treatment groups.  

Organ Weights:  High-dose males showed slightly increased liver weight to body weight ratios.  Absolute liver weights and liver weight to brain weight ratios were not statistically different from controls.

Clinical Chemistries:  The following parameters were statistically altered from controls, in one or both sexes, most often in the high dose group.  The alterations are slight in nature but are consistent with liver toxicity, although histopathology did not confirm damage to this organ.  Urea:  Slightly elevated in mid and high dose males and females at 4 and 13 weeks.  Cholesterol:  Slightly elevated in high dose male and females at 4 weeks and females at 13 weeks.  Gamma-glutamyl transferase:  Slightly elevated in high dose males at 4 and 13 weeks.  Glucose:  Slightly elevated In high dose females at 4 and 13 weeks.  Potassium:  Slightly elevated in high dose males and females at 4 and 13 weeks.

Hematology:  No treatment-related changes noted. Urinalysis:  High dose males were the only subjects that showed effects possibly related to treatment.  When compared to negative controls, urine of high dose males showed: slightly lower urinary pH (4 & 13 weeks), moderately increased numbers of transitional epithelial cells (4 weeks), slightly to moderately decreased sodium excretion (4 & 13 weeks), and moderately increased magnesium excretion (4 & 13 weeks).  Other changes occurred but were considered unrelated to treatment.

Ophthalmological Examinations:  No treatment-related lesions noted. Macroscopic Examinations:  No treatment-related lesions noted.

Histological Examinations:  No lesions reported except for "a coarse yellow-brown pigment . . .noted in one female rat from group 4.  This pigment was located mainly in hepatocytes of zone 1 and occasionally in Kupffer cells.  The identity of this pigment was not established."

Effect levels

Dose descriptor:
NOAEL
Effect level:
450 other: mg/kg
Sex:
male/female
Basis for effect level:
other: increase in kidney and liver weights without accompanying histopathology

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Body weights were decreased slightly but statistically in high-dose males (1000 mg/kg-d). Livers were enlarged but without accompanying histopathology in high-dose males. Liver findings were corroborated by clinical chemistry results in which some parameters reflective of liver injury
were slightly elevated in the high dose groups of either or both sexes (urea was elevated in mid-dose subjects but did not exhibit a dose-response). Some urinary parameters in high dose rats were altered (only in high-dose subjects). Most of these findings occurred after 4 as well as after 13 weeks of exposure to DPnB. The NOAEL is 450 mg/kg-day and the LOAEL, based on decreased body weights, increased liver weights (without histopathology) and slight alterations in clinical chemistry parameters, is 1000 mg/kg-d.
Executive summary:

Four groups of Sprague-Dawley rats (20/sex/dose level) received dipropylene glycol n-butyl ether (DPnB) in their feed at concentrations equivalent to target doses of 0, 200, 450, or 1000 mg/kg-day for 13 weeks.  Five additional rats per sex were added to each group.  These additional rats received DPnB in their feed for only four weeks and then
were sacrificed in order to assess DPnB toxicity at this interim period.  Nominal doses and weekly ranges of doses
are reported in the table below.  Concentrations of DPnB in feed were adjusted on a weekly basis, based on food
consumption patterns, to achieve the desired dose.  For males, concentrations of DPnB in feed ranged from: 1) 2200-3400 ppm for the 200 mg/kg-d group, 2) 4950-7200 ppm for the 450 mg/kg-d group, and 3) 11000-16000 ppm for the
1000 mg/kg-d group.  For females, concentrations of DPnB in feed ranged from: 1) 2150-2700 ppm for the 200 mg/kg-d
group, 2) 4840-6000 ppm for the 450 mg/kg-d group, and 3) 10750-13200 ppm for the 1000 mg/kg-d group.

Rats were observed for mortality twice daily and for clinical signs of toxicity once per day.  Once weekly,
animals were given a more detailed clinical examination with palpation for masses.  Body weights, water, and food
consumption were monitored weekly.  Ophthalmological examinations were conducted prior to treatment and at
sacrifice (interim animals included).  Hematology, clinical chemistry, and urinalysis evaluations were conducted at 4
and 13 weeks.  At sacrifice, all control and high dose animals were subjected to complete necropsy and
histopathological evaluations.  Gross lesions were recorded at necropsy.  Selected organs were weighed and over 40
tissues were collected from all animals and fixed for histopathological evaluation.  Only tissues from control and
high-dose animals were evaluated histopathologically.

Absolute and relative liver weights were increased in high dose males.   In females at the high dose level, absolute
and relative kidney weights were increased with no accompanying histopathology.  Slight alterations in clinical
chemistries, electrolytes, and hematology also were noted in both sexes at the high dose level.  No changes in any other
monitored parameters were noted at any dose level.  The NOAEL for DPnB is 450 mg/kg-day and the LOAEL is 1000
mg/kg-day (for organ weight changes).

Morbidity/Mortality:  All rats survived treatment with the test compound.

Clinical signs:  No treatment-related signs reported.

Food Consumption:  A slight increase in relative food consumption (to body weight) but not absolute food consumption was noted in high dose males.

Water Consumption:  No effect on water consumption was noted.

Body weights:  Body weights in high dose males were slightly decreased during the first three weeks of treatment. 
Although not statistically significant thereafter, this trend continued in the high dose males throughout the study.
 Body weights were unaffected in high dose females or in either sex from lower treatment groups.
 
Organ Weights:  High-dose males showed slightly increased liver weight to body weight ratios.  Absolute liver weights
and liver weight to brain weight ratios were not statistically different from controls.

Clinical Chemistries:  The following parameters were statistically altered from controls, in one or both sexes,
most often in the high dose group.  The alterations are slight in nature but are consistent with liver toxicity,
although histopathology did not confirm damage to this organ.  Urea:  Slightly elevated in mid and high dose males
and females at 4 and 13 weeks.  Cholesterol:  Slightly elevated in high dose male and females at 4 weeks and
females at 13 weeks.  Gamma-glutamyl transferase:  Slightly elevated in high dose males at 4 and 13 weeks.  Glucose: 
Slightly elevated In high dose females at 4 and 13 weeks. 

Potassium:  Slightly elevated in high dose males and females at 4 and 13 weeks.

Hematology:  No treatment-related changes noted.

Urinalysis:  High dose males were the only subjects that showed effects possibly related to treatment.  When compared
to negative controls, urine of high dose males showed: slightly lower urinary pH (4 & 13 weeks), moderately
increased numbers of transitional epithelial cells (4 weeks), slightly to moderately decreased sodium excretion (4
& 13 weeks), and moderately increased magnesium excretion (4 & 13 weeks).  Other changes occurred but were considered
unrelated to treatment.

Ophthalmological Examinations:  No treatment-related lesions noted.

Macroscopic Examinations:  No treatment-related lesions noted.

Histological Examinations:  No lesions reported except for "a coarse yellow-brown pigment . . .noted in one female rat
from group 4.  This pigment was located mainly in hepatocytes of zone 1 and occasionally in Kupffer cells. 
The identity of this pigment was not established."

The results from this study indicate low toxicity for DPnB. 
No evidence was found for hemolytic activity.

The NOAEL is 450 mg/kg-day and the LOAEL is 1000 mg/kg-d, based on decreased body weights, increased liver weights (without histopathology) and slight alterations in clinical chemistry parameters.

This study was identified as key for this toxicity endpoint because of the methods followed (which were comprehensively
documented in the report).  The report included GLP and Quality Assurance statements, signed by the Study Director
and Head of the QA Unit, respectively.  The study and report followed OECD Protocol 408: "Repeated Dose 90-day Oral
Toxicity Study in Rodents."  The numbers and type of test animals used and their husbandry conditions were as
prescribed in the guidance.  Test material characterization was adequate. The dose of test material complied with
guidance, the length of the treatment period (90 days) was sufficient, and evaluation criteria and statistical methods
were typical for this type assay and adequately recorded.