Diphenyl ether

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The publication lists no information on guideline/s and GLP but the report contains sufficient data for interpretation of study results.

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:

publication

Title:

Unnamed

Year:

2003

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

For the absorption, distribution and elimination study, Sprague-Dawley rats received a dermal application of [14C]DPE under a semi-occlusive dressing for 6 h. DPE was diluted in diethyl phthalate (DEP) to administer a total application volume of 2 ml/kg and concentrations of 0.5, 5 and 50% ( ~ 10, 100 and 1000 mg DPE/kg body weight).

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Diphenyl ether

EC Number:

202-981-2

EC Name:

Diphenyl ether

Cas Number:

101-84-8

Molecular formula:

C12H10O

IUPAC Name:

phenoxybenzene

Details on test material:

Source: [14C]DPE was obtained from Amersham International plc (Poole, UK)
Specific activity: 67.1 uCi/mg
Radiochemical purity: 99% via thin-layer chromatography

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

Male Sprague-Dawley CD rats (approx. 9 weeks old) were obtained from Charles River (UK) Ltd (Margate, Kent, UK). Their backs were shaved with animal clippers 24 h prior to the dose administration.

Administration / exposure

Type of coverage:

semiocclusive

Vehicle:

other: diethyl phthalate (DEP)

Duration of exposure:

6 h

Doses:

Groups of four rats were dosed topically with [14C]DPE formulated in diethyl phthalate (DEP) at three concentrations: 0.5, 5 and 50%. These concentrations constituted dose levels of approximately 10, 100 and 1000 mg/kg body weight.

No. of animals per group:

4 male rats/group

Control animals:

no

Details on study design:

Doses of 2 ml/kg were applied to gauze squares ( ~ 4 cm x 4 cm) with an aluminium foil back. These patches were placed on the shaved skin on the
animals' backs and held in place by a semi-occlusive dressing (50 mm Micropore, 3M) and tape (50 mm Blenderm, 3M). The gauze squares and dressing were removed after 6 h, and the dosed area was washed with DEP to remove the non-absorbed DPE. The rats were then placed in Jencon's all-glass metabolism cages designed for the separate collection of urine, feces and expired air. Urine, feces and expired air were collected for 72 h after dosing over the following time periods:
Urine. 0 6 h, 6-24 h, 24-48 h, 48-72 h
Feces: 0-24 h, 24- 48 h, 48-72 h
Expired air: 0-24 h, 24-48 h, 48-72 h

At 72 h post-dose, animals were killed by CO2 narcosis, and a blood sample was removed from the vena cava. Selected tissues (liver, kidneys, gastrointestinal tract, treated skin, and non-treated skin) and the remaining carcass were retained for analysis of total radioactivity.

Details on in vitro test system (if applicable):

Not applicable

Results and discussion

Signs and symptoms of toxicity:

not specified

Dermal irritation:

not specified

Absorption in different matrices:

No data

Total recovery:

After 72 h post-application, the 14C-label from DPE was eliminated primarily in the urine in all test groups (15.84-18.65%), with small amounts also found in the feces (1.18-3.79%).

At 72-h post dosing, approximately 0.2% of the administered dose was retained in the body with low levels also measured in the liver, kidney and gastrointestinal tract (0.01-0.05, 0.01-0.05 and 0.24-0.35%, respectively). In addition, a small amount of 14C-label was found in the cage and air; the total amount recovered ranged from 0.19 to 2.80% This likely indicates that the 14C-label either volatilized from the skin and/or was in the expired air from the animals.

Total recovered: 96.28, 94.05 and 93.85% following administration of 10, 100 or 1000 mg/kg body weight, respectively.

Percutaneous absorption

Dose:

10, 100 or 1000 mg/kg

Parameter:

percentage

Absorption:

ca. 19 - 23 %

Remarks on result:

other: 72h

Remarks:

This range was calculated from the amount of radioactivity found in urine, feces, tissues, carcass and washed, treated skin.

Conversion factor human vs. animal skin:

No data

Any other information on results incl. tables

The results from the dermal ADE study clearly indicate that the 14C-label from DPE was absorbed at a rate that was higher than that reported for in vitro studies

(Hotchkiss, 1998, Absorption of fragrance ingredients using in vitro models with human skin. In: Frosch, P.J., Johansen, J.D., White, I.R. (Eds.), Fragrances: Beneficial and Adverse Effects. Springer, Germany, pp. 125-135. ). The amount of radiolabeled material that penetrated the skin during a 72-h in vitro rat and human absorption study amounted to 0.3 and 0.2% for rat and human skin, respectively. By contrast, the present study indicated that the 14C-label had steady dermal penetration over 72-h that totaled 19-23% of the administered dose. This range was calculated from the amount of radioactivity found in urine, feces, tissues, carcass and washed, treated skin. Most of the absorbed radiolabel was eliminated in the urine (~ 20% of administered dose) with a small amount being excreted in feces (~ 14%). One possibility for the fecal excretion is dermal absorption that is followed by biliary excretion into the gastrointestinal tract. The other possibility is that the anirnals ingested small amounts of the 14C-label during grooming that was observed after the dressing was removed.

The poor in vitro-in vivo correlation may reflect inter-laboratory differences in experimental procedure or the material's high lipophilicity (calculated log Kow

4.05, Syracuse Research Corporation) (Hotchkiss, 1998). DPE is very slightly soluble in water (water solubility 20.8 ppm at 25 C, Dow Chemical USA), which may make diffusion from the skin into an aqueous receptor fluid difficult in the in vitro skin absorption model. In addition, vehicle may play a role in the differences observed. In this rat in vivo study, DEP was used as a vehicle. It is not clear if a vehicle was used by Hotchkiss (1998).

About 0.2% of the dose was retained in the animal body 72 h after dosing with low levels of radioactivity also measured in the liver, kidney and gastrointestinal

tract (~ 0.02-0.30%). Small amounts of radioactivity (approx. 1% dose) were still associated with dosed skin after 72 h; 30-60% of this aniount was apparently

bound to the skin. Small amounts were also associated with non-dosed skin (0.13-0.27%), and may be due to the rats spreading the 14C-labeled material during

grooming after the semi-occluded binding was removed.

Applicant's summary and conclusion

Conclusions:

Following administration of 10, 100 or 1000 mg DPE/kg body weight, approximately 17.7% of the administered dose was eliminated in the urine, with small amounts also found in the feces (1.18-3.79%). At 72 h post-dosing, approximately 0.2% of the applied dose was retained in the body with low levels also measured in the liver, kidney and gastrointestinal tract ( ~ 0.04, 0.02 and 0.3%, respectively).

Executive summary:

Diphenyl ether (DPE) was investigated to determine the dermal absorption parameters and subchronic toxicity of this fragrance ingredient. For the absorption, distribution and elimination study, Sprague-Dawley rats received a dermal application of [14C]DPE under a semi-occlusive dressing for 6 h. DPE was diluted in diethyl phthalate (DEP) to administer a total application volume of 2 ml/kg and concentrations of 0.5, 5 and 50% ( ~ 10, 100 and 1000 mg DPE/kg body weight). Approximately 17.7% of the administered dose was eliminated in the urine, with small amounts also found in the feces (1.18-3.79%). At 72 h post-dosing, approximately 0.2% of the applied dose was retained in the body with low levels also measured in the liver, kidney and gastrointestinal tract ( ~ 0.04, 0.02 and 0.3%, respectively). The 13-week subchronic toxicity study was performed with groups of 12 Sprague- Dawley rats/sex/dose that received semi-occluded daily dermal applications of DPE for 6 h/day. All groups were dosed at a constant 2 ml/kg body weight volume of DPE in the DEP vehicle at concentrations to administer 0, 100, 300 or 1000 mg DPE/kg body weight/day. At the high dose level, there was a slight reduction in body weight gain in males (13%), increase in albumin (5-6%) and

phosphate (10-15%) levels in both sexes, a reduction of cholesterol in females (14%), an increase in kidney (17%) and brain (8%) weights in males, and an increase in liver weight (18-19%) in both sexes. No histopathological lesions were seen in any organ examined. At 300 mg/kg body weight/day, the only notable findings were an increase in liver weight (10%) in both sexes and a slight increase in albumin (5%) in females. In addition, skin irritation reactions at the site of application were observed in all DPE dose groups. The systemic no-observed-effect level (NOEL) in this study is 100 mg/kg body weight/day. Owing to mitigating factors, the systemic findings were judged to lack biological significance and the no-observed-adverse-effect level (NOAEL) was determined to be 1000 mg/kg body weight/day.