Mass Transport of Deposited Aerosol Particles by Surface-to-Surface Contact and its Implications for Aerosol-Borne Disease Transmission

ANN MCDONAGH (1), Richard G. Sextro (2), Miriam A. Byrne (1)

(1) National University of Ireland Galway (NUIG) (2) Lawrence Berkeley National Laboratory (LBNL)

     Abstract Number: 243
     Last modified: April 30, 2010

Abstract
The spread of deposited aerosol particles from one surface to another via contact transfer is an important factor in assessing the exposure pathways to airborne contaminants. Contact transfer has been implicated as a mechanism for the spread of infectious diseases but mass transfer efficiencies are poorly understood. We have conducted an initial study to quantify the mass transfer efficiency of deposited aerosol particles when selected surfaces come in contact. A matrix of four variables was investigated; different surface pairs, applied pressure, contact time and contaminant loading. Among these, the variable with the greatest influence on mass transfer efficiency was the choice of surface pairs. Two types of surfaces were investigated, two soft surfaces – 100 % cotton and synthetic fleece – and two hard surfaces – brass and plastic laminate. The lowest mass transfer efficiency was observed for transfer from contaminated fleece to inititally clean plastic laminate, ~ 2 %, and the highest efficiencies were seen for transfers from the two hard surfaces, brass and plastic laminate, to fleece, 41 and 30 % respectively. An increase in the applied pressure between the two surfaces in contact leads to a step change in transfer efficiency, so that two pressure regimes can be identified, with a transition pressure between them that depends on surface type. Time of contact appears to have little to no effect on the mass transfer efficiency for the surfaces studied. Changes in contaminant loading produced variable effects on the transport efficiency – but no clear trend in the data was apparent.
Overall, the contact transfer efficiencies observed are very significant numbers in terms of hazardous aerosol transport in the environment. Additional work using a broader range of surface pairs and biological aerosols would further elucidate the role of contact transfer in the spread of infectious diseases.