Ester reaction products of 1,4-Benzenedicarboxylic acid with C11-14 iso-alcohols, C13-rich

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Reliability rating was 1 because the in vitro percutaneous absorption study was carried out with human cadaver skin and followed the OECD 428 in vitro skin absorption guidelines. Studies was carried out under GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2003

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Principles of method if other than guideline:

The purpose of this study was to investigate the steady-state rate of absorption of DEHT through dermatomed human cadaver skin specimens in vitro and to determine the extent of skin damage resulting from DEHT exposure

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Bis(2-ethylhexyl) terephthalate

EC Number:

229-176-9

EC Name:

Bis(2-ethylhexyl) terephthalate

Cas Number:

6422-86-2

Molecular formula:

C24H38O4

IUPAC Name:

bis(2-ethylhexyl) terephthalate

Constituent 2

Reference substance name:

Di-2-ethylhexyl terephthalate (DEHT)

IUPAC Name:

Di-2-ethylhexyl terephthalate (DEHT)

Details on test material:

The structure of the test substance was confirmed using gas chromatography with mass spectrometric detection (GC/MS). Prior to use on the study, the purity of the unlabeled test substance was determined by gas chromatography with flame ionization detection (GC/FID) and found to be 97.9 ± 0.2%. The initial radiochemical purity of the 14C-labeled test substance was determined by gas chromatography with
radiochemical detection (GC/RAD) and found to be >99.5%. The purity of the 14C-labeled test substance recovered from the donor chambers following the 29 hour skin absorptio n study at 32 degree C was determined by GC/RAD and GC/FID and found tobbe 100% and 97.7-100.2%, respectively. Based on these results, the test substance was considered to be stable during the test period.

Radiolabelling:

yes

Remarks:

14C-DEHT

Test animals

Species:

human

Sex:

not specified

Details on test animals or test system and environmental conditions:

Human cadaver skin was used,

Administration / exposure

Type of coverage:

open

Vehicle:

unchanged (no vehicle)

Control animals:

no

Details on study design:

Study Design:
The study consisted of a three phase experiment:
Phase 1 - Determination of the permeability to tritium;
Phase 2 - Determination of the permeability to the test substance;
Phase 3 - Determination of the permeability to tritium.

Procedure:
In order to control for inter-individual variability in skin absorption, skin samples from three different human donors were used. The experiment utilized nine Franz-type diffusio cells containing three skin preparations from each of the three donors. Samples were collected using a dermatome; the specified thickness was approximately 200 to 500 um.

During each phase of the experiment, the receptor chambers were filled with receptor solution. Duplicate background (0 hr) samples were taken from the receptor chamber from each cell.

Phase 1: 300 μL of tritium was applied to the donor chambers and the chambers were incubated at 32 C for 6 hours. Duplicate samples were removed from the receptor chambers at hourly intervals and analyzed for tritium by liquid scintillation spectrometry (LSS). The receptor chambers were refilled after each sampling. After collecting the last sample, the donor and receptor chambers were rinsed with phosphate buffered saline and refilled with antibiotic-antimycotic saline without Volpo-20. The cells were allowed to stir overnight, after which they were emptied, rinsed, and filled with the appropriate solutions for Phase 2 of the experiment

Phase 2: 300 μL of the neat test substance was applied directly to the surface of the skin of the test substance cells and the chambers were incubated at 32 C for 29 hours. Duplicate samples were removed from the receptor chambers at hourly intervals for 6 hours and then at 8, 11, 17, 25, 26, 27, 28, and 29 hours. The 14C-labeled test substance in the receptor solution was analyzed by LSS. The receptor chambers were refilled after each sampling. Buffered isotonic saline was applied to the control cells donor chambers. Duplicate samples were removed from the receptor chambers at 0, 3, 6, and 29 hours and analyzed for tritium by LSS. The receptor chambers were refilled after each sampling.

At termination of Phase 2, all components of the test system, except skin specimens, were analyzed by LSS for determination of total 14C-labeled test substance recovery. Then the donor and receptor chambers were refilled with antibiotic-antimycotic saline without Volpo-20. The chambers were allowed to stir overnight, after which they were emptied, rinsed, and filled with the appropriate solutions for Phase 3 of the experiment.

Phase 3: 300 μL of tritium was applied to the donor chambers and the chambers were incubated at 32 C for 6 hours. Duplicate samples were removed from the receptor chambers at hourly intervals and analyzed for tritium and the 14C-labeled test substance by LSS. The receptor chambers were refilled after each sampling.

Following the completion of Phase 3, the skin samples were removed, digested using a tissue solubilizer, and analyzed for the test substance. The samples collected following Phase 3 were analyzed by LSS for determination of total 14C-labeled test substance recovery.

The rate of increase in the concentration of the 14C-labeled test substance or tritium in the receptor chamber of each cell was used to calculate a permeability constant (cm/hr) and an absorption rate (μg/cm2/hr) for the test substance and tritium.

Assessment of Membrane Integrity:

The integrity of each skin sample was evaluated by measuring its permeability to tritium over a period of 6 hours during Phase 1 of the experiment. In addition, the ratio of the tritium permeability constants for Phase 3 and Phase 1 were used to calculate a damage ratio for each cell. This value was used to assess the effect of the test substance on the integrity of the skin sample.

Details on in vitro test system (if applicable):

In vitro Franz diffusion cells were used
Test System: Human Cadaver Skin
Receptor Solution: Dulbecco's buffered isotonic saline containing an antibiotic-antimycotic solution and 6% Volpo-20

Results and discussion

Signs and symptoms of toxicity:

not examined

Dermal irritation:

not examined

Applicant's summary and conclusion

Conclusions:

The dermal absorption rate for DEHT was determined using human skin and in vitro Franz diffusion cells. The mean (± SD) absorption rate of DEHT was found to be 0.103 ± 0.053 ug/cm2/hr. The corresponding permeability constant was determined to be 8.39 x 10E-8 cm/hr. The mean (±SD) total test substance recovery was 103.8% ± 6.3%. Using tritiated water to check integrity. DEHT did not alter skin permeability and is not expect to cause any damage to the skin.

Executive summary:

in vitro dermal absorption studies have been performed with the related terephthalate analog, DEHT (CAS No. 6422-86-2) using human skin which could provide some useful read-across information for the submission substance.  EXcess DEHT was applied neat to human skin using in vitro percutaneous glass Franz diffusion cells and determined the dermal absorption rate for DEHT to be 0.103 ± 0.052 μg/cm2/hr. These findings indicate that DEHT was very slowly absorbed through human skin. Based on this absorption rate, it was estimated that if excess DEHT was to be in contact with an area of skin equivalent to both hands (approximately 720 cm²surface area, 70 kg human) continuously for 1 hr, the calculated systemically absorbed dose would be 1.06 μg/kg. Hence, overall bioavailability was considered relatively low or minimal via dermal route of exposure for DEHT. .