1-(2-butoxy-1-methylethoxy)propan-2-ol

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Feb.-Dec. 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to OECD guideline 406

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Principles of method if other than guideline:

n/a

GLP compliance:

yes

Type of study:

Buehler test

Justification for non-LLNA method:

This substance has been demonstrated to be a non-sensitizer in a guideline compliant studies, therefore potency data as generated in an LLNA is not needed

Test material

Test material information

Constituent 1

Reference substance name:

1-(2-butoxy-1-methylethoxy)propan-2-ol

EC Number:

249-951-5

EC Name:

1-(2-butoxy-1-methylethoxy)propan-2-ol

Cas Number:

29911-28-2

Molecular formula:

C10H22O3

IUPAC Name:

1-(2-butoxy-1-methylethoxy)propan-2-ol

Details on test material:

Identity: Dowanol-DPnB (n-butoxypropoxypropanol or
dipropylene glycol normal-butyl ether).
CAS # 29911-28-2
Batch No.: XZ 95411.00
Purity: More than 95%.
Appearance: Clear liquid.
Administered as: Undiluted liquid.
Vapor pressure: 0.06 mmHg at 25°C (79 ppm at 1 atm)
Specific Gravity: 0.91 kg/liter.
Solubility: 5% in water.
Storage: At ambient temperature in the dark.
Stability: Stable up to 200°C.

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.

In vivo test system

Test animals

Species:

guinea pig

Strain:

Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River Wiga GmbH
- Age at study initiation: n/a
- Weight at study initiation: n/a
- Housing: 5 animals per cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum):ad libitum
- Acclimation period: n/a


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 40-80
- Air changes (per hr): n/a
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: To: n/a

Study design: in vivo (non-LLNA)

Induction

Induction 1

Route:

epicutaneous, semiocclusive

Vehicle:

polyethylene glycol

Induction 2

Concentration / amount:

80% for induction, 40% for challenge

Challenge

Challenge 1

Route:

epicutaneous, semiocclusive

Vehicle:

polyethylene glycol

Challenge 2

Concentration / amount:

80% for induction, 40% for challenge

No. of animals per dose:

10

Details on study design:

Initially, a preliminary dose range-finding study was conducted to determine the irritation potential of the test material in order to select the appropriate treatment solution concentration for the main sensitization study. Four concentrations of dipropylene glycol n-butyl ether (DPnB) were tested (using propylene glycol as a diluent).  Concentrations of 100%, 50%, 10%, and 5% were evaluated. 

Minimal irritation occurred at 100% and no irritation occurred at lower concentrations.  Consequently, 80% DPnB was selected as an appropriate concentration to use in the induction phase.  For the challenge phase, 40% DPnB was chosen as a non-irritating dose.  In the sensitization test, the backs of 20 male Hartley guinea pigs (10/sex) were clipped free of hair and 0.3 ml of the 80% DPnB test solution was topically applied to a site on the flank using a Hill Top Chamber® secured with a bandage. The test material was held in contact with the skin for 6 hours whereupon it was removed with lukewarm water.  This procedure was repeated for the second and third inductions, which followed at one-week intervals.  The sites were read for irritation but results were not reported. For the challenge phase, conducted 12 days after the third induction, 0.3 ml of 40% DPnB was applied to a naive site on the flank of the guinea pigs and held in place for 6 hours using a Hill Top Chamber® and then removed, as described above. A control group of five males and five females was treated similarly except that propylene glycol was applied that did not contain DPnB. After the challenge dose, the site of skin application was depilitated using Veet cream and scored at 24 and 48 hours following removal of the test material.  Responses were graded by evaluating erythema or edema on a scale that included: 0 (no reaction), ± (slight, patchy reaction), 1 (slight but confluent, or moderate but patchy reaction), 2 (moderate erythema), or 3 (severe erythema with or without edema).  These responses were compared with untreated sites on the same animal and with propylene glycol-treated negative controls.  Other skin reactions were recorded if present (e.g., edema, eschar, necrosis).

Challenge controls:

Negative controls: propylene glycol , 0.3 ml of 100% pure PG applied for 6 hours

Positive control substance(s):

no

Study design: in vivo (LLNA)

Statistics:

none

Results and discussion

In vivo (non-LLNA)

Results

Results 1

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

40%

No. with + reactions:

0

Total no. in group:

4

Clinical observations:

none

Remarks on result:

other: hypersensitivity in guine pigs

Results 2

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

40%

No. with + reactions:

0

Total no. in group:

19

Remarks on result:

other: DPnB did not induce contact hypersensitivity in guine pigs

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: Not applicable

Results 2

Parameter:

other: Disintegrations per minute (DPM)

Remarks on result:

other: Not applicable

Any other information on results incl. tables

Morbidity/Mortality:  All but one female survived treatment with the test compound.  This female died in the restrainer
over the 6-hour period of the second induction, exhibiting signs of respiratory distress.

Clinical signs:  Respiratory distress in the one non-surviving female.  No dermal effects reported at site of application.

Body weights:  Animals appeared to gain weight normally over the course of the study.
 
Macroscopic Examinations:  Hemorrhage of the lung was found in the single non-surviving female.

Induction reactions and duration:  No effects reported.

Challenge reactions and duration:  At the 24-hour reading, all scores in treated animals were 0 for erythema or edema. 
Scores remained 0 at the 48-hour reading.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

DPnB did not cause contact skin sensitivity under the conditions of this test.

Executive summary:

Initially, a preliminary dose range-finding study was conducted to determine the irritation potential of the test
material in order to select the appropriate treatment solution concentration for the main sensitization study.
Four concentrations of dipropylene glycol n-butyl ether (DPnB) were tested (using propylene glycol as a diluent). 
Concentrations of 100%, 50%, 10%, and 5% were evaluated. 

Minimal irritation occurred at 100% and no irritation occurred at lower concentrations.  Consequently, 80% DPnB
was selected as an appropriate concentration to use in the induction phase.  For the challenge phase, 40% DPnB was
chosen as a non-irritating dose. 

In the sensitization test, the backs of 20 male Hartley guinea pigs (10/sex) were clipped free of hair and 0.3 ml of
the 80% DPnB test solution was topically applied to a site on the flank using a Hill Top Chamber® secured with a
bandage. The test material was held in contact with the skin for 6 hours whereupon it was removed with lukewarm water. 
This procedure was repeated for the second and third inductions, which followed at one-week intervals.  The sites
were read for irritation but results were not reported. For the challenge phase, conducted 12 days after the third
induction, 0.3 ml of 40% DPnB was applied to a naive site on the flank of the guinea pigs and held in place for 6 hours
using a Hill Top Chamber® and then removed, as described above. A control group of five males and five females was
treated similarly except that propylene glycol was applied that did not contain DPnB.

After the challenge dose, the site of skin application was depilitated using Veet cream and scored at 24 and 48 hours
following removal of the test material.  Responses were graded by evaluating erythema or edema on a scale that
included: 0 (no reaction), ± (slight, patchy reaction), 1 (slight but confluent, or moderate but patchy reaction), 2 (moderate erythema), or 3 (severe erythema with or without edema).  These responses were compared with untreated sites
on the same animal and with propylene glycol-treated negative controls.  Other skin reactions were recorded if present (e.g., edema, eschar, necrosis). The experimental study design is shown below.

                     Study Design

Group    Test/           No.        Topical       Challenge 
         Control         Animals    Induction     Dose*
         Material                   Dose          Topical)
==========================================================
1.        Dipropylene     20        0.3 ml of 80%  0.3 ml of 40% 
Test     Glycol n-Butyl  (10/sex)  DPnB w/v in    DPnB w/v in
Group    Ether (DPnB)             PG, applied    PG, applied
                                 for 6 hr       for 6 hr.

2.        Propylene      10        0.3 ml of      0.3 ml of 
Negative  Glycol (PG)     (5/sex)   100% pure PG,  100% PG,
Control                          applied for   applied for
                                 6 hr.          6 hr. 

Toxicity Endpoints Monitored

Clinical signs:          Every 2 hours on day 0 (day of test material administration) and once daily on workdays for 14 days thereafter.
Morbidity/mortality:    Every 2 hours on day 0 (day of test material administration) and once daily on workdays for 14 days thereafter.
Body weights:            Taken on dose days -1 and post challenge day 3.
Necropsy:                None conducted.

Morbidity/Mortality:  All but one female survived treatment with the test compound.  This female died in the restrainer
over the 6-hour period of the second induction, exhibiting signs of respiratory distress.

Clinical signs:  Respiratory distress in the one non-surviving female.  No dermal effects reported at site of application.

Body weights:  Animals appeared to gain weight normally over the course of the study.
 
Macroscopic Examinations:  Hemorrhage of the lung was found in the single non-surviving female.

Induction reactions and duration:  No effects reported.

Challenge reactions and duration:  At the 24-hour reading, all scores in treated animals were 0 for erythema or edema. 
Scores remained 0 at the 48-hour reading.

Classification: Labeling not required for this endpoint.

Conclusion: DPnB did not cause contact hypersensitivity under the conditions of this test.

This finding is consistent with propylene glycol ethers in general.  This test was a Buehler-type test, rather than a Magnusson-Kligman maximization test (i.e., no adjuvant used).

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.  While the study report did not specifically cite OECD Protocol 406: "Skin
Sensitization," the numbers and type of test animals used and their husbandry conditions were as prescribed in the
guidance.  Test material characterization was adequate. The amount of test material applied complied with guidance, as
did other procedures reflecting a modified Buehler assay, and findings were adequately recorded.