2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 January 2005 to 20 April 2005 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Methodology conducted according to OECD guidelines under GLP principles

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Details on test material:

- Name of test material (as cited in study report): Tetrabromobisphenol-A (TBBPA)
- Molecular formula (if other than submission substance): N/A
- Molecular weight (if other than submission substance): N/A
- Smiles notation (if other than submission substance): N/A
- InChl (if other than submission substance): N/A
- Structural formula attached as image file (if other than submission substance): see Fig. N/A
- Substance type: Monoconstituent
- Physical state: Radiolabelled test item- dissolved in ethanol; Non-radiolabelled- white powder
- Analytical purity: Radiolabelled= 99.6%; Non-radiolabelled=99.20%
- Impurities (identity and concentrations): Not reported
- Composition of test material, percentage of components:
Non-radiolabelled= 99.20% TBBPA, 0.02% Tribromophenol, 0.75% TriBPA, 0.03% o,p-TBBPA
- Isomers composition: Not reported
- Purity test date: Not reported
- Lot/batch No.: Radiolabelled= No. CFQ14174; Non-radiolabelled= #TS6404
- Expiration date of the lot/batch: Not reported
- Radiochemical purity (if radiolabelling): 99.6% (determined by HPLC)
- Specific activity (if radiolabelling): 1.0mCi/mL in ethanol; 56mCi/mmol when undissolved
- Locations of the label (if radiolabelling): Not reported
- Expiration date of radiochemical substance (if radiolabelling): Not reported
- Stability under test conditions: Not reported
- Storage condition of test material: Radiolabelled test item: at -20C in the dark; Non-radiolabelled test item: at ambient temperature in the dark
- Other:

Radiolabelling:

yes

Test animals

Species:

human

Sex:

female

Details on test animals or test system and environmental conditions:

TEST SKIN
- Source: Skin washing experiment: obtained from female surgery patients aged 19 to 49 years old; Absorbtion experiment: obtained from female surgery patients aged 25 to 57 years old


ENVIRONMENTAL CONDITIONS
- Temperature (°C): Stored at -20C, and thawed prior to use
- Humidity (%): Not reported
- Air flow rate: about 1.5 mL/h
- Photoperiod (hrs dark / hrs light): Not reported

Administration / exposure

Type of coverage:

not specified

Vehicle:

acetone

Duration of exposure:

Single dose applied to skin surface, with vehicle evaporation and observations for 24hours post-application.

Doses:

- Nominal doses: 1.9 mg/cm2
- Actual doses: 2.0 mg/cm2
- Actual doses calculated as follows: Absorbed dose was 0.73% of the applied dose; Dermal delivery was 1.60% of the applied dose
- Dose volume: 6.4 uL
- Rationale for dose selection: None given

No. of animals per group:

10 samples of human skin

Control animals:

no

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions:
- Method of storage:


APPLICATION OF DOSE:


VEHICLE
- Justification for use and choice of vehicle (if other than water): Solubility of TBBPA in acetone is greater than water, and acetone evaporates faster
- Amount(s) applied (volume or weight with unit): 6.4 uL
- Concentration (if solution): 1246 ug/6.4 uL


TEST SITE
- Preparation of test site: Skin placed in a flow-through diffusion cell
- Area of exposure: 0.64 cm2
- % coverage: total?
- Type of cover / wrap if used: N/A
- Time intervals for shavings or clippings: N/A



REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: N/A
- Washing procedures and type of cleansing agent: 50 uL of Radox Supersoap
- Time after start of exposure: 8hr after exposure


ANALYSIS
- Method type(s) for identification: Liquid scintillation counting
- Liquid scintillation counting results (cpm) converted to dpm as follows: Not reported
- Validation of analytical procedure: Not reported
- Limits of detection and quantification: Not reported

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: Plastic surgery patients
- Ethical approval if human skin: Yes
- Type of skin: Breast and upper arm
- Preparative technique: placed in flow-through cell and acetone vehicle evaporated
- Thickness of skin (in mm): Full thickness (690 to 1550 um)
- Membrane integrity check: yes
- Storage conditions: at -20C until use
- Justification of species, anatomical site and preparative technique:


PRINCIPLES OF ASSAY
- Diffusion cell: Flow-through
- Receptor fluid: Ethanol and water, 1:1 v/v
- Solubility of test substance in receptor fluid: water solubility = 1.26 ppm and ethanol solubility = 80% w/w
- Static system: No
- Flow-through system: Yes
- Test temperature: 32C
- Humidity: Not reported
- Occlusion: Yes
- Reference substance(s): None

Results and discussion

Signs and symptoms of toxicity:

not specified

Dermal irritation:

not specified

Absorption in different matrices:

- Non-occlusive cover + enclosure rinse:
- Skin wash: 24.97% of applied dose when washed 8h after exposure
- Skin test site: 24hr mean total unabsorbed dose= 102.26% of radioactivity
- Skin, untreated site: 0.25% of radioactivity
- Blood: N/A
- Carcass: N/A
- Urine: N/A
- Expired air (if applicable): N/A
- Serial non-detects in excreta at termination: N/A
- Receptor fluid, receptor chamber, donor chamber (in vitro test system): ranged from 0.30% to 1.74% of applied dose
- Skin preparation (in vitro test system): See table below
- Stratum corneum (in vitro test system): The bulk of the radioactivity (9.47%) was recovered in the outermost 5 tape strips

Total recovery:

Total recovery ranged from 99.27 to 108.8%

Conversion factor human vs. animal skin:

N/A

Any other information on results incl. tables

Table 1: Distribution of Radioactivity (% Applied Dose) at 24 h Post Dose Following Topical Application of TBBPA in Acetone Vehicle to Human Split‑Thickness Skin

	Cell Number and Donor Number
	Cell 40	Cell 41	Cell 42	Cell 43	Cell 44	Cell 54	Cell 55	Cell 57	Cell 58	Cell 59
	0095	0100	0109	0112	0113	0100	0109	0113	0112	0098	Mean	SD
Skin Wash 8 h	27.95	28.61	17.45	39.54	28.69	27.08	12.70	19.57	17.31	10.89	24.97	8.76
Tissue Swab 8 h	0.84	2.89	5.09	0.11	3.20	3.18	4.58	0.29	2.00	3.44	2.38	1.77
Pipette Tips 8 h	0.08	0.05	0.01	0.31	0.05	0.09	0.04	0.14	0.43	0.05	0.10	0.09
Total Q-Tips	31.19	36.04	27.96	60.37	37.64	32.21	37.77	29.89	46.73	17.33	34.08	12.28
Dislodgeable Dose 8 h	60.05	67.59	50.51	100.32	69.57	62.55	55.08	49.89	66.47	31.71	61.52	19.84
Tissue Swab 24 h	1.49	1.34	1.52	0.15	0.87	1.02	2.39	1.70	6.24	1.28	1.17	0.49
Cell Wash	26.85	18.52	33.36	0.95	22.06	31.07	32.97	26.54	17.09	55.38	26.84	15.30
Total Dislodgeable Dose	88.39	87.45	85.39	101.42	92.49	94.64	90.45	78.13	89.80	88.37	89.53	6.87
Stratum Corneum 1-5	6.78	8.69	9.34	1.41	8.06	5.45	7.37	21.11	10.54	14.88	9.47	6.04
Stratum Corneum 6-10	0.85	1.73	1.46	0.15	0.97	0.73	2.05	4.96	1.51	1.32	1.52	1.47
Stratum Corneum 11-15	0.39	0.43	0.95	0.06	0.99	0.40	1.44	2.44	0.48	1.23	0.86	0.75
Stratum Corneum 16-20	0.42	0.37	0.61	0.05	0.15	0.24	0.46	0.54	0.32	0.91	0.41	0.27
Stratum Corneum 21-25	0.21	0.48	0.22	0.01	0.01	0.32	0.54	0.18	0.25	0.29	0.22	0.16
Total Stratum Corneum	8.65	11.71	12.59	1.69	10.19	7.14	11.86	29.22	13.09	18.62	12.48	8.31
Unexposed Skin	0.09	0.16	0.27	0.06	0.05	0.13	0.09	0.08	0.11	1.16	0.25	0.37
Total Unabsorbed	97.12	99.31	98.24	103.17	102.74	101.91	102.40	107.43	103.00	108.16	102.26	4.03
Exposed Skin	1.14	0.87	1.49	0.26	0.78	1.63	4.22	0.63	2.02	0.16	0.87	0.53
Receptor Fluid	1.00	0.84	1.74	0.49	0.30	0.39	0.75	0.44	3.61	0.54	0.72	0.48
Receptor Rinse	0.01	0.01	0.02	0.00	0.00	0.01	0.02	0.01	0.18	0.02	0.01	0.01
Total Absorbed	1.01	0.85	1.76	0.50	0.31	0.40	0.76	0.46	3.79	0.56	0.73	0.48
Dermal Delivery	2.15	1.71	3.25	0.76	1.09	2.03	4.98	1.09	5.81	0.72	1.60	0.86
Mass Balance	99.27	101.02	101.49	103.92	103.83	103.94	107.38	108.51	108.81	108.88	103.86	3.41

Table 2: Distribution of [¹⁴C]‑TBBPA (µg equiv./cm²) at 24 h Post Dose Following Topical Application of TBBPA in Acetone Vehicle to Human Split‑Thickness Skin

	Cell Number and Donor Number
	Cell 40	Cell 41	Cell 42	Cell 43	Cell 44	Cell 54	Cell 55	Cell 57	Cell 58	Cell 59
	0095	0100	0109	0112	0113	0100	0109	0113	0112	0098	Mean	SD
Dislodgeable Dose 8 h	1202.93	1353.96	1011.84	2009.68	1393.62	1253.09	1103.44	999.34	1331.44	635.30	1232.47	397.44
Total Dislodgeable Dose	1770.57	1751.82	1710.45	2031.63	1852.86	1895.77	1811.87	1565.05	1798.82	1770.29	1793.56	137.62
Stratum Corneum	173.19	234.49	252.13	33.80	204.14	143.11	237.62	585.39	262.30	373.06	249.91	166.49
Total Unabsorbed	1945.48	1989.41	1967.95	2066.63	2058.08	2041.57	2051.27	2151.97	2063.38	2166.61	2048.46	80.82
Total Absorbed	20.18	16.95	35.34	9.94	6.11	7.95	15.29	9.12	75.85	11.23	14.60	9.61
Dermal Delivery	43.06	34.30	65.17	15.21	21.84	40.61	99.72	21.76	116.38	14.48	32.05	17.32
Total Recovery	1988.53	2023.72	2033.12	2081.84	2079.91	2082.18	2151.00	2173.73	2179.75	2181.09	2080.52	68.39

Cell 55 was rejected from mean + SD as this was an outlier for dermal delivery

Cell 58 was rejected from mean + SD as this was damaged during the 8 h washing process

Applicant's summary and conclusion

Conclusions:

in vitro skin permeability study in human (split thickness) skin of 14C-TBBPA: < 1% of dose absorbed. The stratum corneum was an efficient barrier to [14C]-TBBPA penetration.

Executive summary:

In an In Vitro percutaneous absorption study of radiolabelled tetrabromobisphenol A (TBBPA) through human skin conducted to GLP in accordance with OECD Guideline 428, radiolabelled [14C]‑TBBPA was applied in vitro in an acetone vehicle at 10 µL/cm2 to human split‑thickness skin membranes mounted using flow‑through diffusion cells. The acetone evaporated rapidly from the skin surface leaving behind the [14C]‑TBBPA (1.9 mg/cm2).

Following this topical application of [14C]-TBBPA to human split‑thickness skin in vitro, the absorbed dose and dermal delivery were 0.73% (14.60 µg.equiv./cm2) and 1.60% (32.05 µg.equiv./cm2) of the applied dose, respectively. 

At 8 h post dose, the dislodgeable dose was 61.52% of the applied dose. At 24 h post dose, a further 28.01% was dislodged from the skin. Therefore, the total dislodgeable dose was 89.53% of the applied dose. 

The stratum corneum contained a further 12.48% of the applied dose. The bulk of this (9.47%) was recovered in the first 5 tape strips. Since the bulk of the stratum corneum associated material was found in the first 5 tapes strips, this indicated that the [14C]‑TBBPA was on the surface of the skin and that the stratum corneum was an efficient barrier to [14C]-TBBPA penetration.