PI: Richard M, Kamens, kamens@unc.edu; Ilona Jaspers (co-PI) ilona_jaspers@med.unc.edu Michael P. Tolocka (co-PI) fizzchem@hotmail.com, Institution: University of North Carolina at Chapel Hill Chapel Hill, NC, 27599
Submitted to: Interfacial Transport and Thermodynamics Program, # 1414 NSF (EPA# NI-108) NSF project Officer: Dr. Robert M. Wellek, and Deputy Director, CBET, Division of Engineering, NSF
Project Objective: Determine the atmospheric fate of engineered nanoparticles (ENP) and the effect of aging on the toxicity of this class of materials.
Intellectual merit: The first focus is on the chemical kinetics of ENP atmospheric transformations. ENP will react faster than their micron-sized counterparts found in dusts. The PIs aim to understand how they behave as seed for secondary organic aerosol (SOA) reactions. Because ENP act as photocatalysts, the yield of SOA will be affected. The second focus is to understand the toxicity of this class of materials. They will rapidly screen the ENP for the production of reactive oxygen species (ROS) as measured by a chemical method. Easily reducible species, such as Ni3+ in NixOy will enhance ROS production. The last step is to measure the actual toxicological response of human bronchial epithelial cells. As the materials age, the metal center becomes more oxidized and therefore easily reduced, resulting in increased inflammatory and other biological response to ENP.
For the kinetics experiments, both flow tube and smog chamber studies will be performed. The flow tube studies will be used to determine kinetic parameters of uptake onto their surfaces as a function of relative humidity and particle size. In this way, we can use these parameters for the models that will be developed for their chemical transformations in real atmospheres. To simulate those atmospheres, the smog chamber experiments will be used to determine the fate of ENP as well as their toxicity measured using chemical and in vitro biological methodologies. The chemical method involves the reaction of the suspended particulate matter with dithiothreitol. For the toxicity analysis, they will use differentiated human bronchial epithelial cells or A549 cells grown on membrane support. Cells will be exposed to the fresh or aged ENP. Basolateral supernatants and RNA will be analyzed for the levels of inflammatory cytokines and chemokines and for the levels of intracellular inflammatory mediators as well as markers of oxidative stress.
Broader Impacts: The unique aspect of this research is that the PIs aim to understand the fate of ENP in the atmosphere and their toxicological effect. Accurate measurements of the oxidation and transport of ENP in the atmosphere are essential. The present uncertainties in understanding ENP fate and transport can strongly affect conclusions from studies that may underestimate the potential toxicity of this class of materials, their derivatives, and their influence on atmospheric processes. Detailed kinetic data will benefit modeling efforts by providing a basis to estimate the fate and transport of ENP. Adding these data to existing databases for air-shed models will benefit officials of governmental organizations who use these models to set policies regarding risk assessment and control strategies for generators of ENP. Health effects researchers will benefit from the toxicological data acquired from our experiments as a guide for exposure assessment. In addition, epidemiological studies that aim to locate a causal mechanism for the deleterious effects of ambient particulate matter will benefit from a more precise understanding of what compounds are associated with the aerosol and their toxicity. The proposed research program not only enables the identification of ENP reactions and their kinetics in real time, but also the rapid reaction and data analysis provides greater throughput allowing a greater range of nanoparticle studies.
Supplemental Keywords: air, ambient air, atmosphere, tropospheric, chemical transport, exposure, effects, health effects, human health, dose-response, stressor, chemicals, toxics, particulates, oxidants, intermediates.
