Thiram

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2 Aug - 17 Sep 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Thiram

EC Number:

205-286-2

EC Name:

Thiram

Cas Number:

137-26-8

Molecular formula:

C6H12N2S4

IUPAC Name:

thiram

Radiolabelling:

yes

Remarks:

thionyl-14C

Test animals

Species:

human

Administration / exposure

Duration of exposure:

6 h

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: labelled stock solution was evaporated to dryness, dry unlabelled thiram was added and taken up with 200 mL acetone. Radioactivity was measured and the solvent was evaporated to a small volume. Aliquots were transferred to vials and formulated to give a Thiram 80WG formulation that was mixed with water to give a workable slurry.

VEHICLE
- Justification for use and choice of vehicle (if other than water): water
- Amount(s) applied (volume or weight with unit): 6.4 µL
- Concentration (if solution): high dose: 617 g/L (nominal 500 g/L); low dose: 1.46 g/L (nominal 1.6 g/L)

TEST SITE
- Area of exposure: 0.64 cm²

REMOVAL OF TEST SUBSTANCE
- Washing procedures and type of cleansing agent: swabbing with 1% Tween 80 in distilled water on cotton wool buds until no further radioactivity was removed
- Time after start of exposure: 6 h

SAMPLE COLLECTION
- Receptor fluid: collected at hourly intervals for the duration of the experiment (24 hours)
- Terminal procedure: skin samples were tape stripped to remove residual surface dose and stratum corneum

ANALYSIS
- Method type(s) for identification: LSC

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: Skin samples were obtained from human donors post mortem and were supplied by the International Institute for the Advancement of Medicine.
- Ethical approval if human skin:
- Type of skin: full thickness (see Table 1)
- Preparative technique: dermatome
- Thickness of skin (in mm): 0.2-0.4
- Membrane integrity check: with tritiated water
- Storage conditions: Skin samples were stored at ca. -20°C
- Justification of species, anatomical site and preparative technique: specified in OECD TG 428

PRINCIPLES OF ASSAY
- Diffusion cell: Scott-Dick flow-through diffusion cell, flow rate 1.5 mL/h
- Receptor fluid: 0.01 M phosphate-buffered saline, supplemented with 5% bovine serum albumin
- Solubility of test substance in receptor fluid: solubility was verified for the high-dose level
- Test temperature: 32°C
- Humidity: 41.2%-54.1% (high dose); 49.8%-56.4% (low dose)
- Occlusion: open

Results and discussion

Absorption in different matrices:

see Table 2

Total recovery:

see Table 2

Percutaneous absorption

Percutaneous absorption 1

Time point:

24 h

Dose:

500 mg/mL

Parameter:

percentage

Absorption:

2.82 %

Remarks on result:

other: 24 h

Remarks:

Flux: 0.201 µg/cm²/h

Percutaneous absorption 2

Time point:

24 h

Dose:

1.6 mg/mL

Parameter:

percentage

Absorption:

11.9 %

Remarks on result:

other: 24 h

Remarks:

Flux: 0.048 µg/cm²/h

Conversion factor human vs. animal skin:

not applicable

Any other information on results incl. tables

Table 2: Summary of results

	Recovery of [^14C]-Thiram [% of dose, mean ± SD]
	Slurry of commercial formulation (500 g/L) n=6	In-use dilution (1.6 g/L) n=4
Skin wash	90.24 ± 3.54	70.88 ± 8.22
Donor compartment wash	2.22 ± 2.56	0.13 ± 0.25
Receptor fluid (0-24 h)	0.06 ± 0.02	3.77 ± 2.27
Receptor compartment wash	0.06 ± 0.00	0.04 ± 0.02
Skin^1)	nd	1.02 ± 0.97
Stratum corneum
Tape strips (1 + 2)	2.28 ± 0.73	14.49 ± 6.80
Tape strips (3 – last)	1.53 ± 1.01	2.16 ± 1.68
Absorbed dose^2)	0.12 ± 0.16	4.82 ± 3.24
Potentially absorbed dose^3)	1.65 ± 1.17	6.98 ± 4.92
Dermal absorption value	1.65 + 1.17 = 2.82 =3	6.98 + 4.92 = 11.9 =12
Total recovery	96.39 ± 1.58	92.47 ± 4.49
^1)Skin without stratum corneum ^2)The absorbed dose is the amount in receptor fluid plus receptor compartment wash plus skin (excluding tape strips, i.e. stratum corneum) ^3)The potentially absorbed dose is the amount in receptor fluid plus receptor compartment wash plus skin and tape strips (excluding the first 2 tape strips) nd: not detected

Applicant's summary and conclusion

Conclusions:

The dermal absorption values for the test substance when formulated as Thiram 80 WG were estimated to be 3% and 12%, respectively, for the commercial formulation and the 1.6 g/L in-use dilution. For DNEL calculation, the result on the commercial formulation was considered.