Physical Characteristics of Ultrafine Particles Emitted from Different Gas Cooking Methods

Gas cooking is a significant source of airborne particles indoors. In order to assess health risk due to exposure from indoor particulate air pollution and to identify effective control strategies, data on size-differentiated aerosol particles released from different cooking methods are critically needed. In this study, controlled experiments were carried out in a domestic kitchen using a scanning mobility particle sizer (SMPS) to investigate the size distribution of ultrafine particles emitted from cooking. Five different cooking methods were studied: steaming, boiling, stir-frying, pan-frying, and deep-frying. During the course of these experiments, the amount and type of food, and the heat setting on the gas stove were kept constant. Results showed that deep-frying caused the largest increase (a 24-fold increase) in particle number concentration to 6.0 x 10 cm compared to a background concentration of 2.5 x 10 cm and contained the highest proportion of nanoparticles (90%). This increase was then followed by pan-frying (1.1 x 10 cm, 78%), stir-frying (9.3 x 10 cm, 69%), boiling (6.9 x 10 cm, 62%), and steaming (5.4 x 10 cm, 55%), implying that cooking with oil produced more particles than cooking with water. It was also observed that steaming and boiling produced a peak in the number concentration of particles at < 10 nm with a second peak at 70 to 80 nm which can be attributed to condensation of water vapor on pre-existing particles. Particle distribution profiles obtained during frying operations were less-distinct compared to steaming and boiling, and demonstrated a modal diameter between 10 and 25 nm. Overall, this study provided comprehensive data on the physical characteristics of particles emitted from cooking, and could be used to evaluate the potential health impacts resulting from exposure to particles indoors.