Registration Dossier

Administrative data

Endpoint:
dermal absorption
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: QSAR, published in peer reviewed literature, adequate for assessment.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6

Data source

Reference
Reference Type:
publication
Title:
A simple dermal absorption model: Derivation and application
Author:
ten Berge, W.
Year:
2009
Bibliographic source:
Chemosphere 75, 1440-1445

Materials and methods

Principles of method if other than guideline:
Dermal absorption was predicted using a QSAR.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Any other information on results incl. tables

The model predicted a permeability coefficient of 0.0835 cm/hour. For the calculation of the percentage absorption, an aqueous Kp of 0.0835 cm/hour was used.

Derivation of the initial absorption

 

As is deduced in EHC 235 (2006), the following equation is true:

 Kp= Km* D/h                                                                         [1]                             

(Kpis the permeability coefficient; Kmis the pseudo-homogeneous partition, or distribution coefficient between the stratuionm corneum and the vehicle; D is the effective diffusion coefficient; h is the membrane thickness)

 

To derive the Kpfor the neat substance, the aqueous Kphas to be divided by the stratum corneum/water partition coefficient (Km). The Km(stratum corneum/water) for TAEE was calculated to be 16.3 by using the QSAR described by ten Berge (2009).

Since the aqueous Kpwas 0.0835 cm/hour, the Kpfor neat liquid is: 0.0835 / 16.3 = 0.00513 cm/hour.

 

To derive the initial absorption of neat TAEE, the Kpfor neat liquid has to be multiplied by the density. The density of TAEE is 764 mg/cm3.

Therefore the initial absorption of neat TAEE is 0.0835 cm/hour x 764 mg/cm3= 3.91 mg/cm2/hour

 

The above mentioned explanation can alternatively be expressed as follows:

Initial absorption (mg/cm2/hr) = rholiquid* (D/h)                            [2]

(rholiquidis the density of the liquid (mg/m3); D is the diffusion coefficient of the liquid in the stratum corneum (cm2/hr); h is the tickness of the stratum corneum)

 

D/h = Kp/Km                                                                                          [3]

(Kpis the permeability coefficient; Kmi s the stratum corneum/water partition coefficient)

 

Substitution of equation 3 in 2 gives:

Initial absorption (mg/cm2/hr) = rholiquid* Kp/Km                                           [4]

 

The density of TAEE is764 mg/cm3; the Kpand Kmwere determined to be 0.0835 cm/hour and 16.3, respectively.

As such, the initial absorption (mg/cm2/hr) = 764 * 0.0835/16.3 = 3.91 mg/cm2/hour

 

In conclusion, the initial absorption of neat TAEE is 3.91 mg/cm2/hour.

Correction for evaporation

Since TAEE is very volatile, a strong competition between evaporation and skin absorption will occur in case the skin is exposed to neat TAEE.

Based on the REACH Guidance appendix R14.1, it was calculated that the evaporation rate of TAEE is 219 mg/cm2/hour.

Therefore, of each dose of TAEE exposed to the skin 1.8% (3.91/219) is available for skin absorption because of the majority of the TAEE evaporates before absorption can occur.

As such, the percentage of dermal absorption of TAEE is assumed considered to be 1.8%. For the calculation of the dermal DNEL, a percentage of dermal absorption of 2% is used (as a worst case figure).

 

In conclusion, the percentage of dermal absorption of TAEE is 2%.

References

EHC 235 Environmental Health Criteria 235: Dermal Absorption, World Health Organization 2006.

ten Berge W, 2009. A simple dermal absorption model: derivation and application. Chemosphere 75(11), 1440-5.

Applicant's summary and conclusion