Ultrafine particles from electric appliances and cooking pans: experiments suggesting desorption/nucleation of sorbed organics as the primary source

Abstract

Ultrafine particles are observed when metal surfaces, such as heating elements in electric appliances, or even empty cooking pans, are heated. The source of the particles has not been identified. We present evidence that particles >10 nm are not emitted directly from the heating elements or the metal surfaces. Using repeated heating of an electric burner, several types of cooking pans, and a steam iron, the increase in the number of particles (>10 nm) can be reduced to 0. After the devices are exposed to indoor air for several hours or days, subsequent heating results in renewed particle production, suggesting that organic matter has sorbed on their surfaces. Also, after a pan has been heated to the point that no increase in particles is observed, washing with detergent results in copious production of particles the next time the pan is heated. These observations suggest that detergent residue and organics sorbed from indoor air are the sources of the particles. We hypothesize that organic compounds are thermally desorbed from the hot surface as gaseous molecules; as they diffuse from the hot air near the pan into cooler air, selected compounds exceed their saturation concentration and nucleation occurs.

Fine and ultrafine particle exposures on 73 trips by car to 65 non-smoking restaurants in the San Francisco Bay Area

“…This result is consistent with experiments reported by Wallace et al. (), which showed that heated metal surfaces (e.g., empty cooking pans) can produce high UFP emissions with no measurable FP emissions, while frying meat is associated with high FP emissions (Abdullahi et al., ; Dacunto et al., ; Zhang et al., ). The UFP and FP means in most restaurants varied widely, and the correlation between the UFP and FP restaurant means measured on the 73 visits was not statistically significant (Figure S2 in Data S1).…”

Quantification of the impact of cooking processes on indoor concentrations of volatile organic species and primary and secondary organic aerosols

“…We note that Asian‐style cooking could generate much higher particulate emissions than Western‐style cooking (100 mg kg −1 ); therefore, our results cannot be generalized to other locations. We also note that we have not observed particle emissions from heated empty pans due to desorption/nucleation of sorbed organics recently suggested as a primary source of particles from cooking processes . Therefore, we have not considered this additional source in our model, although such processes can still occur if pans are not cleaned well.…”

“…Cooking‐induced primary and secondary pollution is not only controlled by the cooked ingredients and cooking style or setting (fuel, pan, oil used, and cooking method), but also depends on the air exchange rates (eg, induced by ventilation) and the oxidant precursor levels indoor and outdoor . Even though, several models describing indoor air pollution from different sources exist, none of these addresses both the particle and gas‐phase emissions from cooking, where the aforementioned parameters driving the pollutants emission, their transformation, and their losses can be systematically varied.…”

Pollutant concentrations and emission rates from natural gas cooking burners without and with range hood exhaust in nine California homes

“…This difference may result from the cleaning, pre-conditioning, and more repeat experiments in the earlier study. This observation derives from the hypothesis that the particles were formed by volatilization of organics compounds that were deposited on cooktop, oven or broiler burner surfaces, as reported by (Wallace et al, 2015) for electric burners and other hot surfaces.…”