Evaluation of physicochemical factors affecting dermal penetration and carcinogenic potency of mineral oils containing polycyclic aromatic compounds

A comparison of the polynuclear aromatic compound (PAC) content and dermal carcinogenicity was made for a series of complex oil mixtures. Results showed a significant correlation (r(2) = 0.76) between the 3-7 ring PAC content and the carcinogenic potency, as determined in a mouse skin-painting bioassay, for oil samples ranging from those with median (50% recovered) boiling points above -500 degrees F to those with initial boiling points of -1070 degrees F. Two variables not considered in the original correlation study, oil viscosity and oil dermal penetration rate, were subsequently measured and their correlation with the carcinogenic potency of the oils determined using simple and multiple regression techniques. Although a weak correlation was observed between oil viscosity and the dermal penetration rate of H-3-benzo[a]pyrene from the oils (colinear variables), no statistically significant correlation was observed between viscosity or penetration rate and carcinogenic potency. It is suggested that the repeated dosing of mice in a two-year skin-painting bioassay results in the attainment of a steady-state concentration of the oils in the skin compartments such that the concentration of 3-7 ring PAC at the sites of cutaneous metabolism, and the concentration of carcinogenic metabolites is proportional to the 3-7 ring PAC content of the applied oil.