In regard to dermal absorption, we have to take into account that, in general, the absorption of pyrethroids through skin is limited; for example, it was estimated that 1.8% of the applied dose was absorbed in volunteers after dermal application of cypermethrin (Woollen et al. 1992).
Dermal absorption of dichloromethane has been demonstrated in animals (McDougal et al. 1986) and in humans (Stewart and Dodd 1964), making this pathway another potential exposure pathway of concern, particularly in occupational settings without adequate protective gear and with improper use of consumer products (e.g., paint strippers).
Studies of dermal absorption of phthalates have largely focused on direct contact of the skin with the chemicals, but some models predict that transdermal uptake directly from ambient air may be a potentially important route of exposure.
Further, dermal metabolism and the influence of barrier perturbation on percutaneous absorption have been analyzed.
Hence, present-day acute exposure to pesticides by dermal absorption and by inhalation has been greatly reduced in the valley.
Although earlier assessments of human exposure to phthalate esters have included the dermal pathway (e.g., Guo and Kannan 2011; Koch et al. 2013; Wittassek et al. 2011; Wormuth et al. 2006), it is only recently that dermal absorption directly from air has been part of such assessments (Bekö et al. 2013; Gaspar et al. 2014).
For the determination of dermal absorption of chemicals, several guidelines have been established by prescribing the type of skin membrane, species, and experimental protocol (OECD 2004).
Contradictory conclusions regarding dermal absorption and toxicity of nanoparticles have been reported (Baroli 2009; Baroli et al. 2007; Crosera et al. 2009; Larese et al. 2009; Senzui et al. 2010), and additional research has been recommended to better characterize and determine health concerns associated with dermal nanomaterial exposure (Crosera et al. 2009).
Although the acquired data do not directly reveal new mechanistic information on dermal absorption, the unique and complete study design has provided a suitable data source for the development of dermal absorption prediction models.
The present work has shown that the dermal absorption in vitro method according to OECD guideline 428 may be successfully adapted to the skin of the amphibian X. laevis, providing the basis for further investigations.
