A Study of Ultrafine Particle Exposure in Indoor Environments

Exposure to airborne particulate matter (PM) emitted during cooking can lead to adverse health effects. An understanding of the exposure to PM during cooking at home provides a foundation for the quantification of possible health risks. The concentrations of airborne particles covering the ultrafine (14.6–100 nm) and accumulation mode (100–661.2 nm) size ranges and PM2.5 during and after cooking activity were measured in 20 homes in Hong Kong. 12 of them with naturally ventilation and no smoking activity were chosen for more detailed analyses. The monitored homes all practiced Chinese-style cooking. Cooking elevated the average number concentrations of ultrafine particles (UFPs) and accumulation mode particles (AMPs) by 10 fold from the background level in the living room and by 20–40 fold in the kitchen. Cooking emitted particles dispersed quickly from the kitchen to the living room indicating that the health impact is not limited to people in the kitchen. Particles in cooking emissions were mainly in the ultrafine size range in terms of the number count while AMPs contributed to at least 60% of the surface area concentrations in the kitchen and 73% in the living room. This suggests that AMPs could still be a major health concern since the particle surface area concentration is suggested to have a more direct relationship with inhalation toxicity than with number concentration.;Combustion activities such as smouldering cigarettes, incense burning and cooking are important sources of particulate matter in indoor environments. Vacuum cleaning is a very common activity in homes, and contributes to the non-combustion-related sources of particulate matter. UFPs can be generated from the motor of a vacuum cleaner, and can be resuspended from the floor during vacuum cleaning. In this study we investigated the rates at which ultrafine particles are emitted from cigarettes, incense and vacuum cleaners in a small test chamber. UFP emissions from cooking were obtained by conducting experiments in a residential kitchen. A multizone model was used to predict the UFP concentrations in a household setting over time. Some data from the experiments of cigarette smouldering and incense burning were used to verify this model. Residual and Kolmogorov-Smirnov (KS) tests were employed to quantify the goodness-of-fit. The results showed a good fit between the measured data and the simulation results. This multizone model is a good approach to predict variations of UFP concentrations in indoor environments. The dose response of people in different zones can be estimated easily based on this model.;Particulate matter generated during cooking contained various carcinogens. These particles consist of both ultrafine particles (nanoparticles) and coarse particles. Exposure and risk assessment studies often use particle mass concentration as dosimetry, which ignores the impact of ultrafine particles due to their insignificant mass compared to coarse particles. This study aims at characterizing the cancer risk with regard to cooking-generated particulate matter using homes in Hong Kong as an example. A risk assessment scheme modified from an existing risk model was developed to consider the cancer risk contributed from both fine ultrafine and coarse particles. Exposure assessment was conducted based on particle concentration data measured in Hong Kong homes. 16 homes without smoking were chosen from the 20 site measurement set. The predicted cancer risk was then compared to the cancer incidence rate in Hong Kong to examine its appropriateness. It is found that the ultrafine particles contribute a much higher risk than that of coarse particles and the modified risk assessment scheme gives an estimate much closer to the incidence rate than the conventional scheme. Use of a grease extractor cannot completely contain the particles and a significant portion of particles can be transported from kitchens to other regions of the homes. (Abstract shortened by UMI.).