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Toxicological information

Dermal absorption

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Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed to GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report Date:
2006

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Physical state: liquid
- Analytical purity: 99.75%
- Impurities (identity and concentrations):
- Composition of test material, percentage of components:
- Isomers composition:
- Purity test date: not given
- Lot/batch No.: 06 130A-03-xx
- Expiration date of the lot/batch: 02 jan 2008
- Radiochemical purity (if radiolabelling): 99.3%
- Specific activity (if radiolabelling): 58mCi/mmol
- Locations of the label (if radiolabelling): 1,2 14C
- Expiration date of radiochemical substance (if radiolabelling): not given
- Stability under test conditions: confirmed by radio-HPLC
- Storage condition of test material: ambient temperature
- Chemical name: Tris(2-chloro-1-methylethyl)-phosphate
- Molecular formula: C9H18Cl3O4P
Specific details on test material used for the study:
- Name of test material (as cited in study report): Fyrol PCF
- Substance type: flame retardant
- Physical state: clear colourless liquid
- Analytical purity: 99.75%
- Impurities (identity and concentrations):
- Composition of test material, percentage of components:
- Isomers composition:
- Purity test date: not given
- Lot/batch No.: 06 130A-03-xx
- Expiration date of the lot/batch: 02 Jan 2008
- Radiochemical purity (if radiolabelling): 99.3%
- Specific activity (if radiolabelling): 58 mCi/mmol
- Locations of the label (if radiolabelling): [1,2-14C]
- Expiration date of radiochemical substance (if radiolabelling): 14 Sept 2010
- Stability under test conditions:
- Storage condition of test material: ambient for non-radiolabelled TCPP; -18°C for radiolabelled TCPP
- Other:
Radiolabelling:
yes
Remarks:
14C

Test animals

Species:
human
Strain:
not specified
Sex:
not specified
Details on test animals and environmental conditions:
Human skin membranes were prepared from frozen skin samples, present at TNO Quality of Life. Human skin was obtained from three donors directly after abdominal surgery.
Donor 1: TNA 10/06, born in 1974, arrival at TNO on 10 April 2006
Donor 2: TNA 21/06, born in 1969, arrival at TNO on 28 August 2006
Donor 3: TNA23/06, born in 1964, arrival at TNO on 7 September 2006

The transportation of the skin to the laboratory was carried out as soon as possible after dissection (ca 2 hours after receipt), while the skin was placed in a plastic container that was kept on ice. The skin of all three donors was stored overnight at 2-10C before sub-cutaneous fat was removed. After removal of subcutaneous fat, the skin was stored in aluminium foil at <-18C until use. Informed consent was provied by all skin donors.

After thawing, human skin was dermatomed using a Dermatome 25mm to a recorded thickness of 400µm. The exact thickness of all skin memebranes was measured with a digimatic micrometer. and recorded.

Administration / exposure

Type of coverage:
not specified
Vehicle:
acetone
Duration of exposure:
8 hrs
Doses:
0.002 mg/cm2
0.1 mg/cm2
1mg/cm2
No. of animals per group:
six membranes/diffusion cells per concentration consisting of 2 membranes from each of three donors
Control animals:
no
Details on study design:
An in vitro percutaneous absorption study (TNO Quality of Life, 2006) conducted to GLP guidelines and to OECD Guideline No. 428, was carried out to determine the rate and extent of absorption following topical application of [14C]-TCPP to human skin for 8 hours. Three dose levels were tested, 0.002, 0.1 and 1.0 mg/cm2, which corresponded approximately to the typical exposure during manufacture of 1K foams, a mid dose to enable a dose response extrapolation and the reasonable worst case exposure during manufacture of TCPP, respectively.
Details on in vitro test system (if applicable):
Human skin membranes, six membranes per dose level, were placed in 9 mm flow-through automated diffusion cells. Receptor fluid was pumped at a speed of ca. 1.6 ml/h. Prior to commencement of the study, the solubility of TCPP in the receptor fluid was determined to be ca. 270 µg/ml, which was considered sufficient. The integrity of the skin membranes was evaluated by measuring the permeability coefficient (Kp) for tritiated water and 18 skin membranes with a Kp value below the cut-off value of 2.5 x 10-3 cm/h were selected for the study.

Results and discussion

Signs and symptoms of toxicity:
not examined
Dermal irritation:
not examined
Total recovery:
The mean recovery of TCPP in human skin was 99.7 ± 6.2%, 99.2 ± 5.7% and 93.5 ± 6.9%, for the high, mid and low doses, respectively.
Percutaneous absorptionopen allclose all
Dose:
0.002mg/cm2
Parameter:
percentage
Absorption:
ca. 22.7 %
Remarks on result:
other: 8hr
Dose:
0.1mg/cm2
Parameter:
percentage
Absorption:
ca. 13.6 %
Remarks on result:
other: 8hr
Dose:
1mg/cm2
Parameter:
percentage
Absorption:
ca. 3.7 %
Remarks on result:
other: 8hr
Conversion factor human vs. animal skin:
-

Any other information on results incl. tables

 Summary of percutaneous penetration of TCPP through human skin in vitro

A

B

C

Concentration measured [mg/ml]

0.066

3.199

31.914

Dose [µg/cm2]

2.049

99.96

997.33

n

6

6

6

Penetration into the receptor fluid after 24 h

% of dose

µg/cm2

% of dose

µg/cm2

% of dose

µg/cm2

18.81

0.39

9.65

9.64

1.78

17.75

Maximal flux [µg/cm2/h]

0.027

0.602

0.836

Lag time [h]

2.7

4.1

2.8

Mean total absorption [%]* (SD)

22.7 (5.8)

13.6 (3.6)

3.7 (1.3)

* Total absorption is defined as the amount in the receptor fluid, the receptor compartment wash and skin membrane, excluding tape strips.

The mean penetration of TCPP into the receptor fluid after 24 hours was 0.39, 9.64 and 17.75 µg/cm2, for the low, mid and high dose, respectively. The mean maximal flux was 0.027, 0.602 and 0.836 µg/cm2/h, for the three doses respectively. The mean total absorption is defined as the compound related radioactivity present in the receptor fluid, the receptor compartment wash and the skin membranes (excluding tape strips). At 0.002 mg/cm2, the total absorption ranged from 17 % to 32.8%, with a mean total absorption of 22.7 %. At the mid dose of 0.1 mg/cm2, the total absorption ranged from 9.8% to 18.2%, with the mean total absorption of 13.6%. At 1 mg/cm2, the total absorption ranged from 2.3% to 5.2%, with a mean total absorption of 3.7%.

Applicant's summary and conclusion

Conclusions:
In in vitro dermal absorption studies, the amount of penetrated substances found in the receptor fluid are considered to be systemically available. The epidermis (except for the stratum corneum) and the dermis are considered as a sink, and therefore amounts found in these tissues should also be considered absorbed (SCCNFP/0750/03 Final, October 2003). Therefore, a worst case mean total absorption value of 23 % is derived from this study for exposure to "neat" TCPP. This is considered to be a reasonable worst case value since 16 of 18 individual membrane measurements taken were found to be 23% or lower.
Executive summary:

In in vitro dermal absorption studies, the amount of penetrated substances found in the receptor fluid are considered to be systemically available. The epidermis (except for the stratum corneum) and the dermis are considered as a sink, and therefore amounts found in these tissues should also be considered absorbed (SCCNFP/0750/03 Final, October 2003). Therefore, a worst case mean total absorption value of 23 % is derived from this study for exposure to "neat" TCPP. This is considered to be a reasonable worst case value since 16 of 18 individual membrane measurements taken were found to be 23% or lower.