The damaging potential of pesticide formulations on human skin

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.

Grantor dc:publisher.institution

University of Bradford

Author dc:creator

• Eagle, Sandra C.

Advisor dc:contributor.advisor

• Barry, Brian W.

• Human Skin
• Absorption
• Pesticides
• Surfactants
• Formulation
• Damage
• Protection

Statement dc:rights

• <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>.

Language dc:language.iso

en

Repository record dc:identifier.uri

https://bradscholars.brad.ac.uk/handle/10454/20252

OAI identifier oai:identifier

oai:bradscholars.brad.ac.uk:10454/20252