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Administrative data

mechanistic studies
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This is a non-guideline study, which meets generally accepted scientific principles.

Data source

Reference Type:
study report
Report date:

Materials and methods

Principles of method if other than guideline:
The study was conducted according to the method described by Hoover DM et al. (Comparison of the in vitro and in vivo models to assess venous irritation of parental antibiotics. Fundam. Appl. Toxicol. 14: 589-597, 1990) and by Pape WJW et al. (Validation of the red blood cell test system as in vitroassay for the rabbit screening of irritation potential of surfactants. Molec. Toxicol. 1: 525-536, 1987)
GLP compliance:
Type of method:
in vitro
Endpoint addressed:
not applicable

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): 2-phenoxyethanol (2-PE)
- Analytical purity: ≥99.9 %

Test animals

other: rabbit, mouse, rat, dog, human (female)
not specified
not specified

Administration / exposure

Route of administration:
other: in vitro
other: PBS
Analytical verification of doses or concentrations:
Duration of treatment / exposure:
0, 0.5, 1, 2, 4 hours
Frequency of treatment:
single treatment
Post exposure period:
Doses / concentrations
Doses / Concentrations:
First trial: 20, 15, 7.5, 3.75, 1.875 and 0.938 mg/ml; Second trial: 15, 12.5. 10.0, 7.5, and 5.0 mg/ml
analytical conc.
final concentrations of test solutions
No. of animals per sex per dose:
1-3 per trial
Control animals:
other: concurrent vehicle control: PBS (negative control)
Details on study design:
Reference substances:
2-Phenoxyacetic acid (2-PAA)
2-Ethoxyethanol (2-EE)
2-Ethoxyacetic acid (2-EAA)

For a human risk assessment the sensitivity of red blood cells (RBC) from mice, rats, rabbits, dogs and human to in vitro hemolysis by 2-phenoxyethanol (2-PE) was determined. Conversion of 2-PE to 2-phenoxyacetic acid (2-PAA) occurs rapidly in vivo and is considered to be an inactivation path for the hemolytic activity of 2-PE. Therefore, a comparison of the in vitro potency of the parental chemical and this metabolite was performed.
2-Ethoxyethanol (2-EE) and 2-ethoxyacetic acid (2-EAA) – chemically closely related to 2-butoxyethanol and 2-butoxyacetic acid - were also chosen for comparison. 2-EE has also been shown to be hemolytically active in rats though probably to a lesser degree than 2-PE.
The resistance of the RBC to lysis was determined with various concentrations of test compounds at different time intervals. The method employed is based on the integrity of the RBC membrane and determines the degree of cell damage and the resulting hemolysis after agitation of the cell suspensions at different test compound concentrations and time intervals. After damage of the RBC membrane by the test procedure, hemoglobin is released into the test solution. The concentration of released hemoglobin is measured, and correlated directly with damage caused to the RBC membrane by the test material.
Stock solutions of the respective test compounds were prepared in phosphate buffered saline (PBS). After pH-adjustment they were mixed in a ratio of3 volumes of test solution to 1 volume of RBC preparation to yield final test concentrations from 20 mg/ml to 0.938 mg/ml. The assay mixtures were incubated at room temperature with agitation for 0.5, 1, 2, and 4 hours, respectively. After incubation and centrifugation of the samples the release of hemoglobin into the supernatant was determined spectrometrically. Results were compared to a sample totally lysed with distilled water and to a fragility control with PBS (spontaneous, not substance related hemolysis (base line)). All samples were evaluated in triplicate.


The release of hemoglobin into the supernatant as a degree of hemolysis was determined spectrometrically at a wavelength of 540 nm. Results were compared to a sample totally lysed with distilled water (100 % hemolysis) and to a fragility control with PBS (spontaneous, not substance related hemolysis (base line)). All samples were evaluated in triplicate.
Calculation of percentage hemolysis.
The percentage hemolysis produced by each test solution was calculated for each sample as follows:
The measured absorbance (A) of test solution (Test) and positive control (PC = 100 % hemolysis) were adjusted (adj.) against absorbance (A) of the fragility control (FC):
A(adj. Test) = A(Test) –A(FC)
A(adj. PC) = A(PC) – A(FC)
The adjusted absorbance of the test solution (A(adj. Test)) was then compared to the absorbance of the positive control (A(PC)) to give the percentage hemolysis (H).
H(%) = A(adj. Test) / A(adj. PC) × 100
Positive control:
Distilled water

Results and discussion

Details on results:
Total hemolysis caused by 2-phenoxyethanol (2-PE) was observed in a concentration range of 12.5 to 10.0 mg/mL in Red Blood Cell (RBC) suspensions of the different species investigated.
The results of the hemolysis tests showed the following scaling of resistance to lysis from highest to least: human > dog > rat ≈ rabbit > mouse. Human RBCs were, therefore, more resistant to 2-PE than RBCs of rabbit, dog, rat and mouse.
2-PAA, 2-EE and 2-EAA did not show significant hemolytic effects at any concentration and in any species examined.

Applicant's summary and conclusion