Registration Dossier

Administrative data

Endpoint:
dermal absorption
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:

Data source

Materials and methods

Results and discussion

Any other information on results incl. tables

In the absence of measured data on dermal absorption, current guidance suggests the assignment of either 10% or 100% default dermal absorption rates. In contrast, the currently available scientific evidence on dermal absorption of metals (predominantly based on the experience from previous EU risk assessments) yields substantially lower figures, which can be summarised briefly as follows:

 

Measured dermal absorption values for metals or metal compounds in studies corresponding to the most recent OECD test guidelines are typically 1 % or even less. Therefore, the use of a 10 % default absorption factor is not scientifically supported for metals. This is corroborated by conclusions from previous EU risk assessments (Ni, Cd, Zn), which have derived dermal absorption rates of 2 % or far less (but with considerable methodical deviations from existing OECD methods) from liquid media.

 

However, considering that under industrial circumstances many applications involve handling of dry powders, substances and materials, and since dissolution is a key prerequisite for any percutaneous absorption, a factor 10 lower default absorption factor may be assigned to such “dry” scenarios where handling of the product does not entail use of aqueous or other liquid media. This approach was taken in the in the EU RA on zinc. A reasoning for this is described in detail elsewhere (Cherrie and Robertson, 1995), based on the argument that dermal uptake is dependent on the concentration of the material on the skin surface rather than it’s mass.

 

The following default dermal absorption factors for metal cations are therefore proposed (reflective of full-shift exposure, i.e. 8 hours):

From exposure to liquid/wet media: 1.0

From dry (dust) exposure: 0.1 %

This approach is consistent with the methodology proposed in HERAG guidance for metals

(HERAG fact sheet - assessment of occumpational dermal exposure and dermal absorption for metals and inorganic metal compounds; EBRC Consulting GmbH / Hannover /Germany; August 2007)

Applicant's summary and conclusion