The damaging potential of pesticide formulations on human skin. A study of the damaging activity of commercial pesticide formulations and their components on the barrier function of human skin, and methods by which to reduce such damage
Eagle, Sandra C.
Eagle, Sandra C.
Publication Date
End of Embargo
Supervisor
Barry, Brian W.
Rights
The University of Bradford theses are licenced under a Creative Commons Licence.
Peer-Reviewed
Open Access status
Accepted for publication
Institution
University of Bradford
Department
School of Pharmacy
Awarded
1990
Embargo end date
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Abstract
Percutaneous absorption is the major route of pesticide entry into the body. Impairment of skin barrier function may increase
systemic exposure and toxicological risk. This project examines barrier function impairment of human skin in vitro due to
commercial liquid formulations of the pesticides pirimphos methyl and pirimicarb.
Water permeation studies demonstrated stratum corneum damage due to emulsifiable concentrate formulations, damage being time and
concentration dependent. The major excipient responsible was the divalent anionic surfactant Phenylsulphonate CA. Another
divalent anionic surfactant Empicol ML26/F also caused stratum corneum barrier function impairment. Protection against anionic
damage was achieved using polyoxyethylated nonionic surfactants of the Synperonic NP and PS ranges incorporated in mixtures and as
stratum corneum pretreatments.
Mechanisms of surfactant damage and protection were assessed. Both anionic surfactants were shown to partition into the stratum
corneum, damage being related to the extent of partitioning. Differential scanning calorimetry showed that the anionic
surfactants disrupt the intercellular lipid bilayer structure with a small effect on intracellular keratin. Therefore, molecular
penetration through stratum corneum is principally enhanced via the intercellular route. Photon correlation studies evidenced
micellar interaction of the anionic and nonionic surfactant molecules in aqueous solution. This may occur in stratum corneum
surface water, thereby reducing the number of anionic monomers available to partition and cause damage.
Supportive skin damage assessment studies were performed.
Changes in electrical conductance of human stratum corneum confirmed barrier impairment due to the emulsifiable concentrates
and anionic surfactants. An alternative membrane, shed squamate skin was shown to be an unsuitable model for human skin damage
assessment.
To reduce human skin damage due to pesticide formulations alternative safer anionic surfactants and polyoxyethylated
nonionic surfactants should be incorporated.
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Thesis
Qualification name
PhD