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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:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Dermal Absorption of Polycyclic Aromatic Hydrocarbons in the Blood-perfused Pig Ear
Author:
VanRooij JGM, Vinke E, De Lange J, Bruijnzeel PLB, Bodelier-Bade MM, Noordhoek J, Jongeneelen FJ
Year:
1995
Bibliographic source:
J. Appl. Toxicol. 15, 193-200

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
Skin model/in-vitro blood perfusion model: by de Lange et al. 1991, J. Pharmacol. Toxicol. Methods 27 71-77
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
Coal tar
Molecular formula:
not applicalbe
IUPAC Name:
Coal tar
Test material form:
liquid: viscous
Specific details on test material used for the study:
- Name of test material (as cited in study report): coal tar
- Physical state: liquid, viscous
Radiolabelling:
no

Test animals

Species:
pig
Strain:
other: domestic
Sex:
not specified
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Slaughterhouse: no details
- Weight at study initiation: 75 - 100 kg
- Experimental conditions: only skin samples (ear) of the animals were used in the in-vitro dermal absorption experiment

Administration / exposure

Type of coverage:
open
Vehicle:
unchanged (no vehicle)
Duration of exposure:
average perfusion time: 250 min
Doses:
~11 mg coal tar/cm² [100 %]
==============================
Substance: Content in coal tar [%] / Single PAH dose [µg/cm²];
fluorene: 2.1 / 230 ;
phenanthrene: 6.8 / 750 ;
anthracene: 3.7 / 410 ;
fluoranthene: 4.0 / 440 ;
pyrene: 2.1 / 230 ;
benzo[b]fluoranthene: 0.9 / 90 ;
benzo[k]fluoranthene: 0.4 / 44 ;
benzo[a]pyrene: 0.9 / 90 ;
indeno[123-cd]pyrene: 0.6 / 66 ;
dibenz[ah]anthracene: 0.4 / 44 ;

Total: ~22 % / ~2400 µg/cm²
==============================

No. of animals per group:
5 pig ears per treatment
Control animals:
no
Details on study design:
DOSE PREPARATION
not applicable, neat substance tested

APPLICATION OF DOSE: topical to the ear

VEHICLE: not applicable

TEST SITE
- Preparation of test site: no particular action
- Area of exposure: 6 x 4 cm²
- Type of cover / wrap if used: none

REMOVAL OF TEST SUBSTANCE
- Perfusion: until perfusion pressure became too high (> 70 mm Hg), max. 250 min
- Removal of protecting device: not relevant
- Washing procedures and type of cleansing agent: not relevant, termination of test
- Time after start of exposure: max. 250 min

SAMPLE COLLECTION
- Collection of blood: 200 min, for pyrene: complete kinetics with 10 - 11 time intervals up to 200 - 250 min

ANALYSIS
- Blood samples (10 ml): Reversed-phase HPLC after 3-fold extraction with n-hexane, evaporation of the solvent and re-dissolution of the residues in methanol (2 ml)
- The method for analysis of the 10 PAHs has an average coefficient of variation of 14.4 %
- Recovery ranged from 45 % for dibenzo[a]anthracene to 97 % for anthracene
- Limits of detection:
[pmol/ml blood]
===============================
fluorene 53.0
phenanthrene 1.7
anthracene 2.0
fluoranthene 51.0
pyrene 2.7
benzo[b]fluoranthene 7.8
benzo[k]fluoranthene 0.3
benzo[a]pyrene 6.3
indeno[123-cd]pyrene 8.3
dibenzo[ah]anthracene 16.5
===============================

STATISTICS:
Paired t-test to determine whether the dermal absorption of the various PAH was statistically different from pyrene absorption
Details on in vitro test system (if applicable):
In-vitro blood perfusion model:
Five ears from domestic pigs were used to study the uptake of 10 PAH in blood after coal-tar application.
The treatment started after 30 min pre-perfusion with oxygenated blood. Perfusion was carried out at 30 °C with heparinized pig blood collected from the pigs.
Coal tar was applied to a skin area of 6 x 4 cm² with an average dose of 11 mg/cm².
Simultaneously, functional control measurements were conducted to assure the physiological integrity of the organ, including blood pressure, blood flow, and glucose uptake.

Results and discussion

Total recovery:
It is not reasonable to estimate total recovery in relation to an applied dose, because the test material was highly overdosed. But owing to the high dosage, the measured fluxes can be supposed to be maximum absorption rates.
==============================
Initial absorption rates of 10 PAHs from coal tar applied to the perfused pig ear:

(Absorption flux at 200 min p.a.)
----------------------------------------------------
Substance: [pmol/(h*cm²)] / [ng/(h*cm²)];
----------------------------------------------------
fluorene: 430 / approx. 71;
phenanthrene: 580 / approx. 103;
anthracene: 110 / approx. 19.5;
fluoranthene: 105 / approx. 21;
pyrene: 60 / approx. 12;
benzo[b]fluoranthene: 3 / approx. 0.8;
benzo[k]fluoranthene: 1 / -- ;
benzo[a]pyrene: 3 / approx. 0.8;
indeno[123-cd]pyrene: 1 / -- ;
dibenzo[ah]anthracene: 1 / --
==============================
Percutaneous absorptionopen allclose all
Key result
Time point:
200 min
Dose:
11 mg coal tar (750 µg phenanthrene)/cm²
Parameter:
rate
Absorption:
ca. 103 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for phenanthrene
Key result
Time point:
200 min
Dose:
11 mg coal tar (230 µg fluorene)/cm²
Parameter:
rate
Absorption:
ca. 71 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for fluorene
Key result
Time point:
200 min
Dose:
11 mg coal tar (440 µg fluoranthene)/cm²
Parameter:
rate
Absorption:
ca. 21 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for fluoranthene
Key result
Time point:
200 min
Dose:
11 mg coal tar (410 µg anthracene)/cm²
Parameter:
rate
Absorption:
ca. 19.5 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for anthracene
Key result
Time point:
200 min
Dose:
11 mg coal tar (230 µg pyrene)/cm²
Parameter:
rate
Absorption:
ca. 12 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for pyrene
Key result
Time point:
200 min
Dose:
11 mg coal tar (90 µg benzo[a]pyrene)/cm²
Parameter:
rate
Absorption:
ca. 0.76 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for benzo[a]pyrene)
Key result
Time point:
200 min
Dose:
11 mg coal tar (44 µg dibenz[ah]anthracene)/cm²
Parameter:
rate
Absorption:
ca. 0.28 other: ng/(h*cm²)
Remarks on result:
other: absorption rate for dibenz[ah]anthracene
Conversion factor human vs. animal skin:
not applicable

Any other information on results incl. tables

Initial absorption rates of 10 PAHs from coal tar applied to the perfused pig ear

 

 

Absorption fluxes at 200 min p.a.

 

pmol/(h*cm²)

ng/(h*cm²)

Fluorene

430

approx. 71

Phenanthrene

580

approx. 103

Anthracene

110

approx. 19.5

Fluoranthene

105

approx. 21

Pyrene

60

approx. 12

Benzo[b]fluoranthene

3

approx. 0.76

Benzo[k]fluoranthene

1

approx. 0.25

Benzo[a]pyrene

3

approx. 0.76

Indeno[1,2,3-cd]pyrene

1

approx. 0.28

Dibenz[a,h]anthracene

1

approx. 0.28

 

The mean absorption fluxes [pmol/(h*cm²)] at 200 min after application of coal tar varied strongly between the 10 PAH.

Furthermore, variation between ears was high, too: for pyrene, for example, the flux ranged between 6 and 155 pmol/(h*cm²) and the cumulative uptake after 200 min was between 26 and 193 pmol/cm². This was not caused by differences in dosing: applied amounts were high overdoses, because 0.2 % of each PAH was absorbed through the skin after 200 min.

The relative cumulative uptake (in relation to pyrene) was 0.01 for indeno[123-cd]pyrene to 12 for phenanthrene, for each PAH except fluoranthene, statistically different from pyrene uptake (p= 0.01). The inter-ear variation was relatively small when the absorbed amount was related to pyrene, indicating that the relative absorption fluxes of the various PAH were quite constant.

Applicant's summary and conclusion