Objective 1: We have submitted a manuscript to Environmental Science and Technology that describes the physical and chemical characteristics of aerosols produced during use of spray products containing nanosilver (Quadros et al., 2011). We derived size-resolved emission factors of total and silver-containing aerosols and showed that the size distribution of aerosols produced is independent of the size distribution of silver nanoparticles in the liquid. Rather, the characteristics of the aerosols produced are a function of multiple characteristics of the liquid and the way it is sprayed. Results can be used to guide the selection of relevant particle doses in nanotoxicity testing, predict exposure to emissions from nanotechnology-based product in indoor air quality models, and develop regulations to ensure consumer safety.
Objective 2: We have developed a new method for aerosolizing nanomaterials that produces fewer artifacts than do existing techniques such as electrospray and atomization of liquid suspensions. Using this method, we have suspended C60 fullerenes in a 6-m3 Teflon chamber and exposed them to varying levels of atmospherically relevant concentrations of ozone. Preliminary results suggest that epoxides and carbonyls form. An important implication of this work is that the aggregation, bioavailability, and toxicity of carbonaceous nanomaterials that have undergone atmospheric aging will differ from original properties.
Objective 3: We have submitted a manuscript to Journal of Nanoparticle Research describing a novel device for delivering aerosolized nanoparticles of a single size to human lung epithelial cells at the air-liquid interface (Holder et al., 2010). We found that silver particles smaller than 100 nm, despite having the lowest mass dose, resulted in a greater toxic response. We believe this to be a promising method of in vitro screening for inhalation toxicity of engineered nanomaterials.
Objective 4: We have designed and built a bench-scale system in which to investigate the fate of nanomaterials during incineration. This project just began, and we are designing model nanowaste streams that include paper and plastic and developing methods for detection of combustion byproducts such as polycyclic aromatic hydrocarbons and dioxins, whose emission rates may be affected by the presence of certain nanomaterials.