Experimental methodologies and preliminary transfer factor data for estimation of dermal exposures to particles

Developmental efforts and experimental data that focused on quantifying the transfer of particles on a mass basis from indoor surfaces to human skin a re described. Methods that utilized a common fluorescein- tagged Arizona Te st Dust (ATD) as a possible surrogate for housedust and a uniform surface d ust deposition chamber to permit estimation of particle mass transfer for s elected dust size fractions were developed. Particle transfers to both wet and dry skin were quantified for contact events with stainless steel, vinyl , and carpeted surfaces that had been pre- loaded with the tagged test dust . To better understand the representativeness of the test dust, a large hou sedust sample was collected and analyzed for particle size distribution by mass and several metals ( Pb, Mn, Cd, Cr, and Ni). The real housedust sampl e was found to have multimodal size distributions (mg/g) for particle-phase metals. The fluorescein tagging provided surface coatings of 0.11 -0.36 ng fluorescein per gram of dust. The predominant surface location of the fluo rescein tag would best represent simulated mass transfers for contaminant s pecies coating the surfaces of the particles. The computer-controlled surfa ce deposition chamber provided acceptably uniform surface coatings with kno wn particle loadings on the contact test panels. Significant findings for t he dermal transfer factor data were: (a) only about 1 / 3 of the projected hand surface typically came in contact with the smooth test surfaces during a press; (b) the fraction of particles transferred to the skin decreased a s the surface roughness increased, with carpeting transfer coefficients ave raging only 1 / 10 those of stainless steel; (c) hand dampness significantl y increased the particle mass transfer; (d) consecutive presses decreased t he particle transfer by a factor of 3 as the skin surface became loaded, re quiring similar to 100 presses to reach an equilibrium transfer rate; and ( e) an increase in metals concentration with decreasing particle size, with levels at 25 mum typically two or more times higher than those at 100 mum - consistent with the earlier finding of Lewis et al. for the same sample fo r pesticides and polycyclic aromatic hydrocarbons (PAHs).