Carbon disulphide

Dermal absorption

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: Well documented, guideline, GLP study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Deviations:

yes

Remarks:

, no neat application of the substance

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

carbon disulfide

IUPAC Name:

carbon disulfide

Details on test material:

- Name of test material (as cited in study report): carbon disulfide

Non-radiolabelled: obtained from Sigma Chemical Company (St. Louis, Missouri)
Purity: 99.9%
H2S + foreign org. S-comp . < 0 .0001 %
sulphate (S04) <0 .00025 %
sulfite ( as S02) < 0 .001 %
benzene < 0 .001 %

Radiolabeled: prepared by Perkin-Elmer Life Sciences (Boston, Massachusetts)
-Specific activity: 3.02 µCi/mmol
-Total activity: 1 mCi
- Physical state: liquid
- Lot/batch No.: 2800-423

Radiolabelling:

yes

Remarks:

14^C

Test animals

Species:

other: in vitro test with human skin samples

Administration / exposure

Type of coverage:

other: in vitro test

Vehicle:

other: isopropyl myristate

Duration of exposure:

Two protocols were followed. One to determine the permeability coefficient and the other to determine short-term (10 and 60 min) penetration rates. The permeability coefficient determination was based of a series of measurements; the last one 8 hours after the start of exposure. The short-term penetration rates were determined for exposure times of 10 and 60 min.

Doses:

- Actual doses: 431.9 mg/ml
verified radiochemical concentration: 0.0527 µCi/mg

No. of animals per group:

The permeability coefficient was determined in an experiment were 6 skin samples from 3 donors were used.
Three experiments were performed to establish the short-term absorption rates, each of them with 4 skin samples from one donor.

Control animals:

no

Remarks:

Not applicable

Details on study design:

DOSE DETERMINATION
The actual dose applied to each skin replicate was determined by subjecting aliquots of the prepared solution to liquid scintillation counting. The total amount of carbon disulfide applied to the skin was determined by the total radioactivity applied and the verified specific activity .

VEHICLE
- Justification for use and choice of vehicle (if other than water): due to to carbon disulfide's low aqueous solubility, isopropyl myristate was the only alternative vehicle choice required by the test protocol.

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: National Disease Research Interchange (NDRI).
- Type of skin: abdominal human cadaver skin.
- Preparative technique: samples of human cadaver skin were stored frozen at approximately -20°C until prepared for use. Samples were removed from donors within 24 hours of death and used within three months. Full thickness skin was immersed in 60°C water for 45 seconds to 2 minutes and the epidermis was peeled away from the dermis.
- Thickness of skin: 20-60 µm.
- Membrane integrity check: yes, by measurement of electrical impedance, before application of the test material; if EI≥17 kΩ the membranes were considered intact.
- Storage conditions: frozen at -20°C.

PRINCIPLES OF ASSAY
A static diffusion cell model was used. The in skin samples had an exposure area of 0.64 cm^2 and the receptor fluid chamber volume was approximately 5 mL .
- Receptor fluid: 0.9% saline with 6% polyethoxyoleate.
- Solubility of test substance in receptor fluid: max solubility of >27000 µl/ml.

Permeability coefficient (Kp) determination: receptor fluid samples (50 µl) were collected 0.5, 1, 2, 3, 4, 5, 6, 7, and 8 h post-application (amount: 1200 µl /cm2, 6 samples from 3 donors)

Short term (at 10 & 60 min) absorption rate determination: 10 µl/cm2 tested in samples collected from 3 donors (4 samples/donor); receptor fluid was collected at 10 min (2 samples/donor) and at 60 min (2 samples/donor)

Results and discussion

Dermal irritation:

not specified

Absorption in different matrices:

- Membrane integrity: declined slightly; the ratio of post-EI to pre-EI values was 0.63
- Skin wash: 0.45
- Skin: < 0.1
- Receptor fluid, donor chamber, stopper, excess dose (in vitro test system): 3.08, < 0.1, 16.1, 72.7

Total recovery:

- Total recovery: 92.4 ± 4.57 (% of applied dose) based on the permeability coefficient test. Based on the slope at steady-state (1434 µg equiv/cm2/h) and the concentration of the applied dose of carbon disulfide in isopropyl myristate (431.9 µg/cm3), the permeability coefficient was calculated: 3.32*10^-3 cm/h (attached Tables 1, 2, 3 & 4).

-Total recovery: 79% based on the short-term exposure experiment

Any other information on results incl. tables

The total equivalents detected in the receptor fluid and in the skin,10 and 60 min after application can be seen in the attached document (Tables 5 -7). The short term -term penetration rate was calculated to be 33.8 µg equiv/cm2/h (10 min) and 4.38 µg equiv/cm2/h (60 min), based on the amount of CS2 on the receptor fluid and in the skin, an exposure area of 0.64 cm2 and an exposure time of 1 h.

Applicant's summary and conclusion

Conclusions:

Based on the results of the study, carbon disulfide is highly absorbed by the skin.

Executive summary:

The permeability coefficient (Kp) and the short-term absorption rates at 10 and 60 minutes have been determined for carbon disulfide using human abdominal skin from cadavers mounted in an in vitro static diffusion cell model . Human cadaver skin was heat-treated, the epidermis was peeled from the dermis and the section mounted onto an in vitro static diffusion cell, stratum corneum uppermost, with an exposure area of 0.64 cm2 . Using a recirculating water bath system, the receptor fluid (0 .9% saline) was maintained at 32°C. Following system equilibration, skin integrity was confirmed by electrical impedance (EI).

For the permeability coefficient experiment, an infinite dose of carbon disulfide in isopropyl myristate vehicle was applied to the epidermal surface, via the donor chamber, at a target rate of 1200 μl/cm2, to 6 skin replicates representing 3 human subjects, and the donor chamber opening was occluded with a rubber stopper. Serial receptor fluid samples were taken at 0 .5, 1, 2, 3, 4, 5, 6, 7, and 8 hours post-application and analyzed for radioactivity by liquid scintillation counting. At the end of the 8-hour exposure, excess carbon disulfide was removed and the skin washed with a 2% soap solution followed by rinsing with water . The receptor fluid was removed and discarded, and the receptor and donor chambers were filled with 0 .9% saline and an end of experiment integrity asssessment was determined using El .

For the short-term exposure experiments, a finite dose of carbon disulfide in isopropyl myristate vehicle (10 μL/cm2) was applied to the epidermal surface, via the donor chamber, to 12 skin replicates representing 3 human subjects, and the donor chamber opening was covered with a volatile organic trap . At the end of the required exposure interval (10 minute and 60 minutes), 6 replicates each were terminated . At termination, the volatile trap was removed and extracted with toluene. The skin surface was washed with a 2% soap solution, rinsed with water, and the receptor fluid was removed and retained for analysis . The receptor and donor chambers were filled with 0 .9% saline and end of experiment integrity asssessment was taken using El . The saline in both chambers was removed and discarded and the skin membrane removed and placed into a glass vial for digestion . The receptor fluid and the skin were analyzed by liquid scintillation counting .

Based on the slope at steady-state (1434 .0 μg equiv/cm2/h) and the concentration of the applied dose of carbon disulfide in isopropyl myristate (431,900 μg/cm3), the permeability coefficient was calculated to be 3 .32 x 10-3 cm/h.

The short term -term penetration rate was calculated to be 33.8 µg equiv/cm2/h (10 min) and 4.38 µg equiv/cm2/h (60 min), based on the amount of CS2 on the receptor fluid and in the skin, an exposure area of 0.64 cm2 and an exposure time of 1 h.