Background: A 2014 study (1) suggested that ultrafine particles (UFP) from heated metal surfaces may be created by desorption of SVOCs from the surfaces, followed by nucleation as the air diffusing from the heat source cools and becomes supersaturated with vapor-phase SVOC molecules. Objectives: 1. Test this theory by applying to surfaces other than metal, including porcelain and glass 2. Estimate the buildup over time of SVOCs encountered in a residence 3. Consider transfer of skin oil to cooking pans as determined by UFP counts Methods: Use electric burner or laboratory hot plate to heat cooking pans, Petri dishes, and aluminum foil, measuring UFP by a condensation particle counter (CPC) and a Scanning Mobility Particle Sizer (SMPS) to provide size-resolved emissions as a function of temperature and time exposed to indoor air. Results: Most of the surfaces tested could be driven to near-zero particle production following repeated heating to temperatures in the range of 150-300 degrees C. Aluminum foil from inner portions of a newly purchased roll appeared to be free of SVOC contamination. Newly purchased Petri dishes had varying amounts of contamination, sometimes near-zero. These "clean" surfaces were then exposed to indoor air for increasing periods of time up to 150 days. Total mass produced ranged from 500 μg for longer exposures. Longer exposures shifted the UFP size distribution to the right (from modes of 5 nm to >50 nm). Total particle concentrations in a 25.8 m3 room ranged from a few thousand to more than a million per cubic centimeter. Washing pans with detergent produced no particles if sterile gloves were employed, but copious particles if bare hands were employed.A single thumbprint on a previously cleaned (by repeated heating) pan could produce one million particles, although most were greater than10 nm in diameter and thus had negligible (greater than 0.1 ug). Multiple thumbprints were capable of producing one hundred million particles and greater than 100 ug mass. (1) Wallace, L.A., Ott, W.R., and Weschler, C.J. (2014) Ultrafine particles from electric appliances and cooking pans: experiments suggesting desorptionucleation of sorbed organics as the primary source. Indoor Air 2015:536-546.
展开▼
