Ethyl [2-(4-phenoxyphenoxy)ethyl]carbamate

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 Mar 2016 to 29 Jun 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Version / remarks:

2004

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Ethyl [2-(4-phenoxyphenoxy)ethyl]carbamate

EC Number:

276-696-7

EC Name:

Ethyl [2-(4-phenoxyphenoxy)ethyl]carbamate

Cas Number:

72490-01-8

Molecular formula:

C17 H19 N O4

IUPAC Name:

ethyl [2-(4-phenoxyphenoxy)ethyl]carbamate

Radiolabelling:

yes

Test animals

Species:

other: Human skin

Administration / exposure

Type of coverage:

open

Vehicle:

other: physiological saline in a 1:1 (w/w) ratio (for the concentrate) and CIPAC D water (for the spray dilutions)

Duration of exposure:

The skin was exposed to the test preparations for 6 hours and receptor fluid samples were collected at 2, 4 and 6 hours post dose. To allow adequate characterisation of the absorption profile, receptor fluid samples were also collected at 8, 12 and 24 hours post dose.

Doses:

- 125 g test substance /kg Formulation Concentrate in saline
- 0.15 g test substance /L Spray Dilution 1
- 0.075 g test substance /L Spray Dilution 2

Results and discussion

Percutaneous absorption

Percutaneous absorption 1

Key result

Time point:

24 h

Dose:

125 g/kg

Parameter:

percentage

Absorption:

0.44 %

Remarks on result:

other: Dermal absorption = (Sum of receptor fluid + receptor chamber wash + exposed skin + skin strips 3-20) + k(n=8) x SD

Percutaneous absorption 2

Key result

Time point:

24 h

Dose:

0.075 g/L

Parameter:

percentage

Absorption:

19 %

Remarks on result:

other: Dermal absorption = (Sum of receptor fluid + receptor chamber wash + exposed skin + skin strips (3-20) + k(n=8) x SD

Percutaneous absorption 3

Key result

Time point:

24 h

Dose:

0.15 g/L

Parameter:

percentage

Absorption:

21 %

Remarks on result:

other: Dermal absorption = (Sum of receptor fluid + receptor chamber wash + exposed skin + skin strips 3-20) + k(n=8) x SD

Any other information on results incl. tables

Table 1. Summary of the test substance through Human Split-Thickness Membranes

Test Preparation	Formulation Concentrate in Saline (125 g/kg)	Spray Dilution 1 (0.15 g/L) (Normalised)	Spray Dilution 2 (0.075 g/L)
Test substance	Test substance
Distribution	% Applied Dose
Dislodgeable Dose 6 h*	99.62	73.49	80.47
Total Dislodgeable Dose**	100.44	82.33	85.55
Donor Chamber Wash	0.39	0.64	0.40
Tape Strips 1-2	0.05	1.15	0.29
Tape Strips 3-20	0.08	1.33	0.54
Unexposed Skin	<0.01	0.08	0.04
Exposed Skin	0.06	3.93	2.45
Receptor Fluid	0.18	10.69	9.38
Receptor Chamber Wash	0.01	0.49	0.43
Mass Balance	100.84	100.00	98.68
Distribution	µg equiv./cm2	ng equiv./cm2	ng equiv./cm2
Dislodgeable Dose 6 h*	1170.88	1098.20	604.66
Total Dislodgeable Dose**	1180.54	1230.19	642.85
Donor Chamber Wash	4.57	9.60	3.04
Tape Strips 1-2	0.63	17.15	2.20
Tape Strips 3-20	0.88	19.94	4.04
Unexposed Skin	0.03	1.23	0.28
Exposed Skin	0.72	58.73	18.40
Receptor Fluid	2.17	159.78	70.47
Receptor Chamber Wash	0.17	7.25	3.22
Mass Balance	1185.14	1494.27	741.47

* Dislodgeable Dose 6 h = Skin Wash 6 h + Tissue Swab 6 h + Pipette Tip 6 h

** Total Dislodgeable Dose = Dislodgeable Dose 6 h + Skin Wash 24 h + Tissue Swab 24 h + Pipette Tip 24 h + Donor Chamber Wash

Table 2. Summary of test substance Absorption through Human Split-Thickness Membranes

Application of Test substance and Actual Concentration of Dose Preparation	Mean Absorption Rates
	Time Period (h)	Absorption Rate
Formulation Concentrate in Saline		µg equiv./cm2/h ± SEM
(115 g/kg test substance)	0-2	0.28 ± 0.04
10.25 µg/cm2(1175 µg ai/cm2)	2-6	0.12 ± 0.02
Unoccluded	6-24	0.06 ± 0.01
Duration of experiment: 24 h, n = 8	0-24	0.09 ± 0.01
Spray Dilution 1		ng equiv./cm2/h ± SEM
(0.149 g/L test substance)	0-2	1.90 ± 0.43
10.00 µL/cm2(1.49 µg ai/cm2)	2-6	10.19 ± 2.06
Unoccluded	6-24	6.40 ± 0.78
Duration of experiment: 24 h, n = 8	0-24	6.66 ± 0.85
Spray Dilution 2		ng equiv./cm2/h ± SEM
(0.075 g/L test substance)	0-2	0.57 ± 0.18
10.00 µL/cm2(0.751 µg ai/cm2)	2-6	4.78 ± 0.23
Unoccluded	6-24	2.79 ± 0.37
Duration of experiment: 24 h, n = 7	0-24	2.94 ± 0.28

Dermal absorption was calculated according to the Efsa guidance on dermal absorption (2017): receptor fluid + receptor chamber wash + exposed skin + skin strips 3-20 + k (n=8) x SD. The following absorption values were calculated: 0.44 %, 19 % and 21 % for 125 g/kg, 0.075 g/L and 0.15 g/L, respectively at 24h. The k multiplication factor (n=8) was determined to be 0.84 and the following SD were calculated: 0.12, 5.76 and 5.38 for 125 g/kg, 0.075 g/L and 0.15 g/L, respectively.

Applicant's summary and conclusion

Conclusions:

The study demonstrated that the amount of the test substance absorbed through human split-thickness skin membranes over 24 h (following a 6 h exposure) from the Formulation Concentrate in Saline (125 g/kg) and the intended in-use concentrations (0.15 g/L and 0.075 g/L), was 0.19%, 11.18%, and 9.81% of the applied dose, respectively, as measured in the receptor fluid and receptor chamber wash. The recalculated values for sum of receptor fluid + receptor chamber wash + exposed skin + skin strips 3-20 + k(n=8) x SD were 0.44%, 19% and 21% for 125 g/kg, 0.075 g/L and 0.15 g/L of the test substance, respectively.

Executive summary:

The purpose of this study was to determine the rate and extent of the in vitro percutaneous absorption of test substance through human split-thickness skin (following 6 h exposure) over an experimental period of 24 h to aid the quantitative assessment of the risk arising from skin contact with the test substance according to OECD TG 428 and GLP principles. The Formulation Concentrate was mixed with physiological saline (1:1, w/w) to generate a paste. A paste was generated because wettable granules cannot be applied accurately to the skin. This is equivalent to an operator becoming exposed to the wettable granule which in turn mixes with sweat.

The active ingredient (the test substance) was assessed with the following applications: 125 g test substance /kg Formulation Concentrate in saline, 0.15 g test substance /L Spray Dilution 1 and 0.075 g test substance /L Spray Dilution 2. The doses were applied at 10 mg/cm2 for the formulation concentrate in saline and 10 μL/cm2 for spray dilution 1 and 2. Following dosing cells were left unoccluded for an experimental period of 24 h, with an interim wash at 6 h post-application. The absorption process was followed by taking samples of the receptor fluid (phosphate buffered saline containing polyoxyethylene 20 oleyl ether (PEG, ca 6%, w/v), sodium azide (ca 0.01%, w/v), streptomycin (ca 0.1 mg/mL) and penicillin (ca 100 units/mL)) at recorded intervals throughout the experimental period. The distribution of the test substance within the test system and a 24 h absorption profile were determined using liquid scintillation counting. Before conducting the main study stability and solubility assessments were carried out.

Results showed that the amount of test substance absorbed through human split-thickness skin membranes over 24 h (following a 6 h exposure) from the concentrate formulation in saline (125 g/kg) and the intended in-use concentrations (0.15 g/L and 0.075 g/L) in the test substance was 0.20%, 11.18% and 9.81% of the applied dose, respectively, as measured in the receptor fluid and receptor chamber wash. The recalculated values for sum of receptor fluid + receptor chamber wash + exposed skin + skin strips 3-20 + k(n=8) x SD were 0.44%, 19% and 21% for 125 g/kg, 0.075 g/L and 0.15 g/L of the test substance, respectively.