In vitro percutaneous penetration of methyl-parathion from a commercial formulation through the human skin

Objective - To compare in vitro percutaneous absorption of methyl-parathion dissolved in an acetone vehicle and in the form of a commercial formulation. Methods - Penetration through the human skin was measured in Franz diffusion cells with full thickness skin from a human cadaver as the membrane. The two tailed non-parametric Mann-Whitney U test was used to compare the cumulative diffusion of methyl-parathion in the receptor fluid of the cells at various time intervals. Results - In vitro skin penetration of methyl-parathion was significantly higher with the commercial formulation. The percentage of the applied dose absorbed after 24 hours was 5.20% v 1.35%. The mean lag time was < 8 hours. Conclusion - Assessments of uptake and internal dose after exposure to pesticides should be based on the commercial products rather than active ingredients, because of the crucial role of the vehicle, as shown in this study.