VOICE-OVER: Welcome to one of ConsExpo Web's online tutorials.
This video will give you insight into the dermal exposure models...
that are used in the ConsExpo Web software.
The dermal exposure route is an important route of exposure...
to many consumer products.
While some products are applied to the skin deliberately...
such as cosmetics and personal care products...
others may come into unintended contact with the skin...
due to spills, contact with contaminated surfaces or deposition.
In addition, substances may migrate from materials...
that come into contact with the skin.
The dermal exposure models that are included in ConsExpo Web...
provide the means to determine direct dermal exposure in various scenarios.
The following dermal exposure models are included.
Instant application, constant rate.
These are followed by the scenario-based models.
Rubbing off, migration, diffusion.
We will now run through the models, starting with instant application.
The instant application model is typically used...
to simulate the use of cosmetics and personal care products...
as consumers apply these directly onto the skin.
It provides a conservative estimate of dermal exposure...
in cases where information on the use of the product is lacking.
The elements that are relevant for dermal exposure are:
the product amount, the weight fraction of the substance of interest...
the skin area that comes into contact with the product...
and the body weight of the consumer who is exposed.
For certain toxicological end points, the relevant dosage metric is dermal load.
It can be estimated by multiplying the applied product amount...
with the substance concentration...
and subsequently dividing by the skin surface area...
that comes into contact with the product.
To obtain the dermal exposure expressed as a dose...
exchange skin surface area with body weight in the formula.
The constant rate model introduces the element of time.
The dermal contact is constant over time...
and expressed as an amount per unit of time.
It is used when the dermal exposure has a continuous character...
such as when applying spray-based products to the skin.
The first two dermal exposure models are relatively straightforward.
The next models are more sophisticated and require detailed information.
The rubbing-off model is used in scenarios...
whereby the substance is rubbed off contaminated or treated surfaces...
during normal activities.
A typical scenario is that of a child playing on a floor or lawn...
that has been treated with a product.
The model describes the process...
of coming into contact with a known contaminated surface during play...
during which the product is rubbed off and transferred onto the skin.
This model introduces two new exposure parameters to describe that process.
The transfer coefficient and the dislodgeable amount.
The transfer coefficient describes the surface area per unit of time...
that the skin effectively comes into contact with.
The dislodgeable amount is defined as the amount...
that is transferred during that contact...
and is expressed as an amount per surface area of the object or floor.
Exposure is then determined by combining the duration of the contact...
the contacted surface area, the transfer coefficient...
and the dislodgeable amount.
The exposure is limited to either the surface area...
that the skin can come into contact with within the period of time...
as specified by the transfer coefficient and the duration of the contact...
or to the maximum treated surface area.
Dermal exposure may also occur during prolonged contact with materials...
for example the clothes that a person is wearing.
During that contact, substances may leach from the textile to the skin.
This scenario is best described using the migration model.
The input parameter that is required for the migration model...
is called the leachable fraction.
This describes the fraction of the product that migrates, that is leaches, onto the skin.
Another factor to note is the skin contact factor.
This parameter accounts for the fact...
that not all skin is in contact with the product or article.
For example, when examining skin contact with bed sheets...
of a person wearing pyjamas...
only a certain fraction of their skin is in direct contact with the bed sheets.
The fifth dermal model included in ConsExpo Web...
describes exposure by means of the transfer of a substance from a product...
only when the substance reaches the outer layer of the product.
This is a type of diffusion model.
Examples of its use include when hands are submerged in a liquid...
or a known product layer comes into contact with the skin.
The model requires information on the concentration...
of the substance in the product, and the product layer thickness.
An important parameter in this model is the diffusion coefficient.
It describes the speed at which the substance transfers...
through the product layer.
Entering the exposure time allows the model to calculate the exposure...
as the diffusion coefficient determines how much of a substance...
has reached the outer layer and forms an exposure risk.
The models that describe dermal exposure through rubbing off...
migration and diffusion...
require parameters that are often difficult to obtain.
ConsExpo Web and the fact sheets...
provide some helpful suggestions for defaults to aid users.
We hope this tutorial has helped you to familiarise yourself with ConsExpo Web.
Our support does not end here.
Visit the ConsExpo website for help pages...
that provide information on ConsExpo Web and a user manual.
You can also access the 'i' and '?' icons within the software...
which are there to give you extra help when needed.
If you still have questions or need assistance...
please contact us at consexpo@rivm.nl.