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Toxicological information

Dermal absorption

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Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Meets generally accepted scientific standards, is well documented and acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
In Vitro Percutaneous Absorption of Nonylphenol (NP) and Nonylphenol Ethoxylates (NPE-4 and NPE-9) in Isolated Perfused Skin
Author:
Monteiro-Riviere, N.A., Van Miller, J.P., Simon, G.S., et al.
Year:
2003
Bibliographic source:
Journal of Toxicology cutaneous and ocular toxicology, 22, Nos. 1 & 2, pp. 1–11

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
Examination of the percutaneous absorption of nonylphenol (NP) and nonylphenol ethoxylates (NPE-4, NPE-9) in the isolated perfused porcine skin flap (IPPSF) model.
The results were compared to the in vitro porcine skin flow through (PSFT) diffusion cell assay
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
Nonylphenol
EC Number:
246-672-0
EC Name:
Nonylphenol
Cas Number:
25154-52-3
IUPAC Name:
2-nonylphenol
Details on test material:
- Name of test material (as cited in study report): Nonylphenol
- Substance type: pure active substance
- Radiochemical purity (if radiolabelling): no data
- Specific activity (if radiolabelling): 2.214 mCi/mmol
- Locations of the label (if radiolabelling): ring-labelled
- Obtained from Biodynamics Radiochemicals, Billingham, UK
Radiolabelling:
yes
Remarks:
14C-ring labelling

Test animals

Details on test animals or test system and environmental conditions:
in vitro test

Administration / exposure

Type of coverage:
open
Vehicle:
polyethylene glycol
Remarks:
PEG-400
Duration of exposure:
IPPSF:8 h perfusion period
PSFT: 8 h treatment
Doses:
IPPSF: Skin flap chambers were dosed with 100µl of 1% radiolabelled Nonylphenol in 79% aqueous PEG-400 solution.
PSFT: 10 µl of 1% NP in PEG-400 with a target radioactivity of 0.5 - 1.0 µCi
Details on study design:
The current studies were conducted in an ex vivo perfused porcine skin model that has been shown to predict human exposure because of its intact vasculature, as well as anatomical and physiological similarities to human skin (Wester et al. Percutaneous absorption of salicylic acid, theophylline, 2,4-dimethylamine, diethyl hexyl phthalic acid, and p-aminobenzoic acid in the isolated perfused porcine skin flap compared to man
in vivo. Toxicol Appl Pharmacol 1998; 151:159–165.).

1% aqueous PEG-400 solutions were used since previous work had indicated that absorption was not altered by vehicle (PEG-400 vs. water) or by concentration (0.1, 1.0, or 10%).
Details on in vitro test system (if applicable):
Isolated perfused porcine skin flap model (IPPSF):
SKIN PREPARATION
- Source of skin: pig
- Type of skin: from porcine ventral abdomen
- Preparative technique: Two single-pedicle axial pattern skin flaps, each lateral to the ventral midline on the pig abdomen, were created during Stage I and harvested 48 h later during Stage II surgery. The flaps were cannulated, flushed with heparinized saline to clear the vasculature of blood, and each transferred to a perfusion chamber.
- Membrane integrity check: The flaps were perfused for 1 h prior to dosing, during which 1.0-ml arterial and 3.0-ml venous samples were collected at 30 and 60 min to determine glucose utilization and zero-time perfusate samples for nonylphenol flux determinations. Upon confirming flap viability, the perfusion was interrupted and each flap was removed from the chamber. A Stomahesive (ConvaTec, Princeton NJ) template with a 1.0 cm x 5.0 cm (5.0 cm²) dose area was secured to the flap with Skin-Bond (Smith & Nephew, Inc., Largo, FL).

PRINCIPLES OF ASSAY
- Diffusion cell: IPPSF perfusion chamber
- Four replicates were used for all assays.
- Perfusate samples were collected for 8 h and analyzed for glucose and radioactivity.
- Perfusate samples were oxidized in a Packard Model 307 oxidizer (Packard Chemical Co., Downers Grove, IL)
- Radioactivity was quantified with a Packard 1900 TR Liquid Scintillation Analyzer (Packard Chemical Co., Downers Grove, IL).

in vitro porcine skin flow through (PSFT) diffusion cell assay
SKIN PREPARATION
- Source of skin: Yorshire pig
- Preparative technique: skin was dermatomed using a Padgett dermatome (Kansas City, MO)
- Thickness of skin (in mm): 500 µm

PRINCIPLES OF ASSAY
- Diffusion cell: PSFT diffusion cell
- Receptor fluid:
- Test temperature: 37 °C
- Humidity: 55–65%
- pH of 7.4–7.5
- Perfusate flow of 4.0 ml/h
- Area of 0,32 cm²
- Occlusion: nonoccluded
- Perfusate: consisted of a Krebs–Ringer bicarbonate buffer with added glucose and bovine serum albumin to promote solubilization of hydrophobic penetrants and provide an in vitro perfusate media with similar properties to the in vivo setting.
- Perfusate and all tissue samples were combusted in an automated tissue oxidizer (Packard Chemical Co., Downers Grove, IL) and then analyzed in a liquid scintillation counter (Packard Chemical Co., Downers Grove, IL) for total 14C determination.

Results and discussion

Signs and symptoms of toxicity:
not examined
Dermal irritation:
not examined
Absorption in different matrices:
IPPSF:
Total compound absorption into perfusate, which would reflect systemic availability, ranged between 0.10 and 0.12% (~1µg) (for NP, NPE-4 and NPE-9). 0.32 – 0.75% (3.3 – 7.64 µg) of the applied dose penetrated into the stratum corneum and underlying dermis and could be absorbed over longer time periods. 64.6 - 77.6% of the applied dose was removed by the surface swabs from the skin surface.

PSFT:
For comparative purposes, the percent absorption and penetration of 1% solution of Nonylphenol for porcine skin in the standard flow through diffusion cells from Monteiro-Riviere (2001) are presented in Table 2. Total compound absorption of NP was 0.14%. 2.76 % of the applied dose penetrated the stratum corneum and underlying dermis.
Total recovery:
IPPSF: Recovery was 84.4% of the applied dose.
PSFT: Recovery was 91.8% of the applied dose.
Percutaneous absorptionopen allclose all
Dose:
100 µl 1% NP
Parameter:
percentage
Absorption:
ca. 0.1 %
Remarks on result:
other: 8 h
Dose:
100 µl 1% NPE-4
Parameter:
percentage
Absorption:
ca. 0.12 %
Remarks on result:
other: 8h
Remarks:
nonylphenol ethoxylate (reference)
Dose:
100 µl 1% NPE-9
Parameter:
percentage
Absorption:
ca. 0.1 %
Remarks on result:
other: 8h
Remarks:
nonylphenol ethoxylate (reference)

Any other information on results incl. tables

Table 1 Mean (+-SEM) residues from nonylphenol in PEG-400 in IPPSF

 

1% NP (n = 4)

Absorption  Surface swabs  S. corneum  Dosed skin  Penetration  Recovery 
 Percent dose  0.10 +- 0.04  77.61 +- 2.68   0.90 +- 0.33  0.32 +- 0.04   0.75 +- 0.21   84.38 +- 1.52 
Mass (µg)   0.96 +- 0.37  735.60 +- 23.90  8.56 +- 3.07  8.56 +- 3.07  7.16 +- 2.03  799.80 +- 12.70

IPPSF = isolate perfused porcine skin flap.

Table 2 Mean (+-SEM) residues from nonylphenols in PEG-400 in PSFT

NP (n = 4)

Absorption  Surface swabs  S. corneum  Dosed skin  Penetration  Recovery 
 Percent dose  0.14 +- 0.02  78.40 +- 5.00   2.21 +- 0.39  0.41 +- 0.13   2.76 +- 0.51   91.76 +- 4.92 

PSFT = porcine skin flow through diffusion cell.

Applicant's summary and conclusion

Conclusions:
NP is absorbed at ~0.1% of the applied dose in an in vitro dermal skin absorption modell. It has been shown that this rate was not significantly altered by vehicle (PEG-400 vs. water) or by concentration (0.1, 1.0, or 10%). About 0.75% of the applied dose penetrated the stratum corneum and underlying dermis. In a worst case scenario all of the penetrated substance could be absorbed leading to a additional systemic exposure. This estimate does not account for a loss of stratum corneum due to exfoliation. However, the overall potential systemic exposure from skin contact to NP can still be considered to be less than 1%.
Executive summary:

In an ex vivo dermal absorption study radioactive ring-labelled Nonylphenol and two nonylphenol ethoxylates (NPE-4, NPE-9) were tested in an isolated perfused porcine skin ap (IPPSF) assay. Application of 1% NP in aqueous PEG-400 solution results in an absorption of ~0.1% after 8 h. It has been shown earlier that this rate was not significantly altered by vehicle (PEG-400 vs. water) or by concentration (0.1, 1.0, or 10%). About 0.75% of the applied dose penetrated the stratum corneum and underlying dermis and could subsequently become systemic available. However, the overall potential systemic exposure from skin contact to NP is still considerable less than 1%. This is in accordance with previous results from in vitro porcine skin flow through (PSFT) diffusion cell assay.

This absorption study is classified acceptable. The ex vivo perfused porcine skin flap model has earlier been shown to be a reliabel tool for the prediction of human exposure because of its intact vasculature, as well as anatomical and physiological similarities to human skin.