ABSTRACT
There is an increasing demand for data that quantify the rates of penetration and
permeation of diverse chemical entities across human skin and can be used to
estimate the potential systemic load following exposure. These estimates can
subsequently be used for risk assessment purposes where the implications of the
everyday use of a wide range of cosmetic products may be determined and
appropriate steps taken to minimize any possible hazard. Risk assessment is the
process by which the probability that a harmful effect may occur is determined (1).
There are four steps involved in risk assessment: hazard assessment, dose-response
assessment, exposure assessment, and risk characterization. It is evident that before
any risk assessment may be made it is necessary to determine whether the
compound under investigation is indeed harmful following systemic exposure
(hazard) and this is usually obtained from studies in laboratory rodents, which
provide a “no observed adverse effect level” (NOAEL), following oral or intrave-
nous administration, which may be subsequently used, in combination with
exposure assessment and skin permeability data, to assess dermal safety margins.
While the NOAEL is obtained from a pragmatic experimental procedure performed
using well established and validated protocols, the assessment of exposure and
determination of skin permeability often leads to values that can be somewhat
variable depending on the precise models and methods used (2-5).
