Volatility Analysis of Ultrafine Particles Emitted During Cooking Activities

Giorgio Buonanno (1), Graham Johnson (2), Lidia Morawska (2), Luca Stabile (1), Pasquale Avino (3)

(1) Dipartimento di Meccanica, Strutture, Ambiente e Territorio, University of Cassino, Italy (2) Queensland University of Technology, Brisbane, Australia (3) DIPIA - ISPESL, via Urbana 167, 00184 Rome, Italy

     Abstract Number: 104
     Last modified: November 3, 2009

Abstract
Although many studies have investigated traffic-related emissions, stack emissions and ultrafine particle (UFP) concentrations in urban ambient air, an important gap in knowledge still exists with respect to indoor environments. UFPs emitted from cooking activities have been associated with many respiratory ailments, including lung cancer. In order to gain a better understanding of the relationship between particulate air pollution and gas cooking, several studies have attempted to measure the particle number concentration and size distribution of particles generated during cooking.
The influence of the temperature, as well as food, oil and stove type on the number, surface and mass (in terms of PM2.5) emission factors when grilling (cooking without oil over a hot plate, heated by a gas or electrical stove) and frying (typically deep-frying, when food is immersed in hot oil, heated by gas stove or electrical frying machine) has already been evaluated. However, even though significant data exist for cooking activities, a lack of understanding of the volatility of the particles emitted during cooking activities remains.
In this study the volatility of particles emitted from cooking activities was specifically examined. A Rotating Disk Thermodiluter (Matter Engineering AG) and a Thermal Conditioner (TC, Matter Engineering AG) together with a Scanning Mobility Particle Sizer (SMPS, TSI Inc.) were used to characterize the number size distributions and total concentrations of particles emitted (in the 0.006-20 micro-meter range) from two cooking processes widely used in Western countries: grilling and frying. Measurements with and without aerosol thermal conditioning were carried out in order to show the dependence of the particle volatility on the cooking method and the type of food being cooked.
Particle volatilisation was observed to occur as the TC temperature was increased during both frying and grilling. For frying, volatilisation was observed in the temperature range 20-250 °C when cooking both fatty and vegetable foods, whereas during grilling, the decay commenced at a higher temperature but continued up to 300 °C. The dependence of the total particle number concentration as a function of the TC temperature was also examined: a refractory residue was observed even after TC treatment at 300 °C in the case of particles emitted from fatty food for both cooking methods. When vegetables were cooked however, the total particle number concentration decreased as the conditioning temperature increased, showing that many of these particles left no detectible refractory residue.
In conclusion, thermal treatment at temperatures up to 300 °C causes particles emitted during cooking to shrink, regardless of the type of food being cooked, however particles produced when cooking fatty foods leave small refractory residue particles but those produced when cooking vegetables can volatilise completely or at least become too small to detect. The differences in the volatility of particles emitted when cooking fatty foods versus those produced when cooking vegetables can be of high interest in studies of human exposure.