Plenary Lectures

The Conference Committee is proud to have five distinguished speakers for the plenary sessions. Each speaker will offer a stimulating and insightful presentation on topics of current and emerging interest to aerosol scientists.

Monday, September 11, 2006
8:00 a.m. – 9:15 a.m.
Assembling Materials and Devices From Nanoscale Building Blocks
Richard W. Siegel

The past decade has seen an explosive growth worldwide in the physical, chemical, and biological synthesis and study of a wide range of nanoscale building blocks with unique properties. The aerosol research community has made significant contributions to this growth. Great strides are now being made worldwide in our ability to assemble these nanoscale building blocks to create advanced materials and devices with novel properties and functionalities. The novel properties of nanostructures are derived from their confined sizes and their very large surface-to volume ratios. The former gives rise to unique size-dependent properties in the nanoscale (1-100 nm) regime, while the latter gives rise to the ability of nanoscale additions to conventional material matrices to dramatically change the host material’s properties. A perspective of this important research area will be presented based upon specific examples from our work in the Center for Directed Assembly of Nanostructures supported by the Nanoscale Science and Engineering Initiative of the National Science Foundation. Examples will be given of directed assembly of nanoparticles, nanotubes, and hybrid structures containing these and biomolecules, to make new materials and devices that possess enhanced mechanical, electrical, optical, and bioactive properties, and multifunctional combinations thereof. The opportunities and challenges facing the worldwide research community in moving forward in this area will be considered.

Biography: Richard W. Siegel is the Robert W. Hunt Professor of Materials Science and Engineering and founding Director of the Nanotechnology Center at Rensselaer Polytechnic Institute. He is also founding director of the National Science Foundation Nanoscale Science and Engineering Center for Directed Assembly of Nanostructures. He graduated from Williams College in 1958 with an AB degree in physics and received an MS degree in physics in 1960 and a PhD degree in metallurgy in 1965 from the University of Illinois in Urbana. Dr. Siegel has been a visiting professor in Germany, Israel, India, Switzerland, and Japan and has been active in local, national, and international professional organizations. He is currently a member of the Nanotechnology Technical Advisory Group of the U.S. President’s Council of Advisors on Science and Technology. Dr. Siegel chaired the World Technology Evaluation Center worldwide study on nanostructure science and technology during 1996-1998 that led to the U.S. National Nanotechnology Initiative in 2001. He was also past chairman (1992-1996) of the International Committee on Nanostructured Materials. Dr. Siegel has authored more than 240 publications and several patents (10 issued, 8 pending) in the areas of defects in metals, diffusion, and nanostructured metal, ceramic, composite, and biomaterials. He has presented more than 450 invited lectures around the world and has also edited 10 books on these subjects. He is an Honorary Member of the Materials Research Societies of India and Japan, and a 1994 recipient of an Alexander von Humboldt Foundation Senior Research Award in Germany. In 2001, he was named a RIKEN Eminent Scientist in Japan. Dr. Siegel also received a 2003 Deutsche Bank Prize “Pioneer of Nanotechnology – Nanomaterials” in Germany.

Tuesday, September 12, 2006
8:00 a.m. – 9:15 a.m.
Indoor Aerosols: Do We Need More Data or More Science?
Lidia Morawska

To state that indoor aerosol is different from outdoor aerosol is not a discovery. With the many sources specific to indoor environment and the myriad of factors, as well as physical and chemical processes affecting this environment, the differences are\ unavoidable. Yet, at times there is very little difference between the characteristics of indoor and outdoor particles: for example for naturally ventilated buildings penetration of particles of all sizes with significance to human heath is almost 100 percent. To develop a complete quantitative understanding of particles in indoor environment, consideration needs to be given to the emissions from indoor sources and penetration of particles from outdoor; the type and operation of the ventilation and filtration system; building characteristics and its operation; and last but not least complex particle dynamic and physico chemistry of the processes occurring indoors.

While outdoor aerosols have been studied for decades, scientific interest in indoor aerosols followed much later and in consequence, there is still less data, knowledge, and quantitative tools available for various types of indoor environments. In general, the assessment and comparison of results from different studies is complicated by large differences in their design, including duration, number of houses investigated, instrumentation used, and thus the measured parameters including particle size ranges. Among other gaps in knowledge, there have been relatively few studies reporting particle number concentration and the scatter of the reported results for size-classified particles is substantial. There is a need to explain and quantify the role of different mechanisms contributing to particle concentration levels and size distribution characteristics in mechanically ventilated large buildings. While there is some data available on indoor source emission factors, the data is still very limited and the variation in emission factors between the same types of sources is substantial; thus predictions through modeling of the level of increase in individual indoor environments is not very reliable. There are a number of existing mathematical models; however, discussion continues about improvements in terms of better model validation, accuracy, input requirements, and also a need for the development of new simulation tools capable of progressing with the new advances in the multidisciplinary and complex field of indoor environments.

Nevertheless, despite these deficiencies a clearer picture of indoor particles, their concentration levels, trends in the concentrations and the factors affecting them, is emerging. In particular, there is a good understanding of the effect of the outdoor particle characteristics on those encountered indoors for naturally ventilated buildings, and on the relative contributions from the most significant indoor sources to the indoor particle concentrations. There is an understanding that the short term impact of indoor sources, particularly combustion sources is even stronger on particle number, than on particle mass, and the resulting concentrations can increase by a few orders of magnitude. There is also an increasing understanding on the production of particles through chemical reactions involving vapors and gases, through processes such as reactions between ozone and various terpenes in indoor environments, which have been shown to result in a significant increase in the number and mass concentrations of sub-micrometer particles.

The presentation reviews the state of knowledge regarding the abovementioned and other key aspects of indoor aerosols and outlines the needs and likely future directions of research and applications in this field.

Biography: Lidia Morawska is a professor at the School of Physical and Chemical Sciences, Queensland University of Technology (QUT) in Brisbane, Australia, and the director of the International Laboratory for Air Quality and Health (ILAQH) at QUT, which is a Collaborating Centre of the World Health Organization. She conducts fundamental and applied research in the interdisciplinary field of air quality and its impact on human health and the environment, with a specific focus on science of airborne particulate matter. Dr. Morawska is a physicist and received her doctorate at the Jagiellonian University, Krakow, Poland, for research on radon and its progeny. Prior to joining QUT, she spent several years in Canada conducting research first at McMaster University in Hamilton as a Fellow of the International Atomic Energy Agency, and later at the University of Toronto.

Dr. Morawska is an author of over 150 journal papers, book chapters, and conference papers. She has also been involved at the executive level with a number of relevant national and international professional bodies and has been acting as an advisor to the World Health Organization. She is the immediate past president of the International Society of Indoor Air Quality and Climate.

Wednesday, September 13, 2006
8:00 a.m. – 9:15 a.m.
Reinventing the Wheel: New Vistas for Aerosol Measurement
Richard C. Flagan

The core aerosol measurement methods, inertial separation, condensational particle detection, and electrical mobility measurements all have their roots in the 19th century, but only entered common usage in the mid- to late-20th century.

Electronic detection of light scattering enabled further advances: instruments that provided real-time assessments of aerosol concentrations and particle size distributions. The resulting flood of data from these instruments revolutionized aerosol science. Where early investigators examined so-called large ions and Aitken particles in broad classes, the electrical mobility analyzer revealed the multimodal nature of the atmospheric aerosol. Refined cascade impactors displayed the size dependence of the aerosol composition, and with that advance, provided insights into the physical and chemical mechanisms of aerosol particle formation and growth. Manufacturers of aerosol instruments made the improved measurement methods available to the aerosol community at large; no longer were advanced measurement methods limited to those researchers who possessed the resources and skills to build their own.

Standardization reduced differences between measurements, and enabled the atmospheric aerosol to be characterized with rigor that had not previously been possible. Just as the nature of the atmospheric aerosol was revealed, the ideal aerosol measurement was defined, but remained unattainable even while aerosol theory advanced to the limits of available aerosol measurements and beyond.

The dawn of the 21st century brought a new era of invention in aerosol measurement. New generations of instruments expanded routine aerosol measurements into the nanometer size regime, improved resolution of particle size and of the transient nature of the atmospheric aerosol. Near-real-time aerosol chemistry measurements, including determination of the chemical composition of individual aerosol particles, provide new insights into the nature of atmospheric particles; advances in laboratory-based analytical chemistry enhanced specificity in chemical species identification. Combined with advances in statistical data analysis, trajectory modeling, and related simulation methods, these have enhanced the links between sources and the atmospheric aerosol. Long duration measurements of ultrafine atmospheric particle size distributions that have been enabled by computer controlled instrumentation have shown that homogeneous nucleation in the atmosphere is not a rare event that can occur only in remote, and very clean environments; instead it has been seen virtually everywhere people have looked for it.

Still, major challenges remain. Aerosol measurements remain the purvue of specialists. Instruments are expensive and required detailed knowledge to operate. While research-level instrumentation has undergone successive revolutionary developments, routine monitoring of the atmospheric aerosol has remained constrained by legal mandates. First PM10, and, more recently, PM2.5 measurements have become the norm. Sampling networks have provided datasets that facilitated epidemiological studies of the health consequences of atmospheric aerosols, especially fine particles. Observations of aggravated respiratory problems in children who live near freeways where diesel trucks emit large numbers of particles in the low nanometer size range suggest that better data are needed. While legal definitions of air pollution problems are required by regulators, rigorous understanding of the health consequences requires much more. At the same time, epidemiological investigations demand measurements that can be widely deployed and continuously operated without fail; gaps in datasets due to instrument malfunction can seriously jeopardize efforts to unravel health consequences. To meet these needs, aerosol instrumentation must not only be made much more reliable than present laboratory tools, it must also be much less expensive to purchase and operate.

Occupational exposure measurements within the emerging nanotechnology industries face similar challenges. Mass measurements do not adequately assess potential threats of particles can translocate across cell membranes in the lungs to enter the circulatory system and other tissues, or into olfactory neurons through which they may migrate to the olfactory cortex. Differential mobility analyzers can characterize the aerosol, but cannot follow a worker to assess integral exposures.

New approaches that will enable these advances are on the horizon. Radical approaches to aerosol measurement are being developed in laboratories around the world. A number of developments push the limits on resolution of aerosol particle size and chemical composition; aerosol mass spectrometry and condensation enhanced particle sampling schemes are rapidly expanding our chemical understanding of the atmospheric aerosol. Others are addressing the challenges I have identified above. For example, new particle size analyzers may enable measurements of aerosol nanoparticles to be deployed into the extended networks required by epidemiologists. New sampling methods should facilitate improved chemical and biological characterization of atmospheric particles. By replacing operationally defined metrics, direct measurements promise to reduce the ambiguity in key atmospheric and exposure parameters. This presentation seeks to highlight a number of ongoing developments in aerosol measurement technology, to place those in context with the historical methods that have fostered the development of aerosol science to its present state, and to explore the evolving challenges to the aerosol measurement community.

Biography: Richard C. Flagan is the Irma and Ross McCollum-William H. Corcoran Professor of Chemical Engineering and professor of environmental science and engineering, in the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena. He received his B.S.E., mechanical engineering, University of Michigan, 1969; S.M. and PhD, from the Massachusetts Institute of Technology, in 1971 and 1973, respectively. His research interests are in control of air pollutants, combustion, and aerosol processes. He is a recipient of numerous awards such as an Honorary Doctorate from Lund University, Sweden; and various awards from aerosol societies such as the David Sinclair Award of the American Association for Aerosol Research (1993); Japan Society for the Promotion of Science Fellow (1992); Marion Smoluchowski Award for Aerosol Research presented by the Gesellschaft für Aerosolforschung (1990). He has published extensively and has more than 200 refereed journal publications.

Thursday, September 14, 2006
8:00 a.m. – 9:15 a.m.
Health Effects of Ambient Particulate Matter
Bret Brunekreef

The health effects of ambient particulate matter (PM) have been subjected to intense research in the last decades. Epidemiological studies have suggested that adverse effects on health occur both after short-term and long-term exposures. The lecture will provide an overview of epidemiologic research methods and findings.

Effects of short-term exposure have been investigated in time series studies, which take advantage of day-to-day or hour-to-hour variations in ambient PM concentrations caused by meteorological phenomena and/or temporal variations in sources e.g. rush hour traffic. The PM ‘input’ data in such studies are usually derived from routine monitoring stations. As a result, they are constrained to what is monitored (usually regulated metrics such as PM10 or PM2.5, particles smaller than 10 or 2.5 Ìm), and to where it is monitored (often urban background sites). The health ‘output’ data are also often derived from routinely collecting registries such as death registries or hospital admissions registries. Sometimes, studies are performed among specially selected subjects such as panels of asthma patients, or patients suffering from cardiovascular disease. As the use of data that have been collected already requires relatively few resources, hundreds of time series studies have been published. The collective evidence suggests that effects on mortality and hospital admissions occur at low levels of exposure, i.e. below current air quality guidelines and standards. Much attention has been paid to potential biases such as confounding by weather variables, gaseous air pollution components, and preferential publication of positive findings. Another issue that has been scrutinized is the extent of ‘mortality displacement,’ i.e. assessment of by how many days or months death is being advanced by exposure to short-term increases in PM pollution. Other biases such as those related to measurement error and to the use of single days to characterize exposure have received less attention.

Effects of long-term exposure have been investigated in a small number of cohort studies. In cohort studies, carefully characterized groups of subjects living in areas with differences in PM exposure are being followed for periods of years to decades. The PM ‘input’ data again are usually routinely collected data, although there are a few examples of studies with dedicated PM monitoring. The health ‘output’ data consist of survival of cohort members or development of clinical or sub-clinical disease. Because cohort members are carefully characterized with respect to potential confounding variables such as smoking, diet, occupation etc., cohort studies offer unique opportunities to single out PM effects. To date, only two or three cohort studies exist in the world that have been specifically designed to study long term effects of air pollution including PM. Other studies were started for different reasons, but have been taken advantage of by adding exposure assessment to ambient PM to it. The main cohort studies published to-date suggest that effects on mortality and disease development occur at PM levels below current guidelines and standards, and that the loss of life expectancy associated with PM exposure may be substantial. In view of this, the data from two major U.S. cohort studies (the Harvard Six Cities Study and the American Cancer Society II Study) have been extensively re-analyzed by a team of independent researchers. This re-analysis has generally supported the original findings, but has also found that effects seem to occur primarily in subjects with only high school education or less. Also, the re-analysis suggested that PM effects were not easily distinguishable from effects of some of the gaseous components in ambient air. European cohort studies have focused on within-city contrasts in traffic-related air pollution mixtures, and have shown associations between these mixtures (characterized by nitrogen oxides or soot measurements) and survival.

Epidemiology is a largely observational science, for the obvious reason that experiments on humans can only be performed to a very limited extent. The causality of associations observed in epidemiological studies therefore needs to be addressed carefully. Elements contributing to a causal interpretation include repetition of findings under various circumstances, explanation of differences in findings by plausible differences in exposure to ‘effect modifiers,’ plausible exclusion of alternative explanations by confounding variables or selection, and support from experimental studies in animals. In view of the complexity of ambient PM it has been difficult to recreate ambient PM exposures in the laboratory. The use of particle concentrators has provided researchers with a unique tool to study PM effects in the laboratory without artifacts generated by PM collection and re-suspension. Evidence is now emerging from longterm PM concentrator studies that support findings from epidemiology.

The results from the PM cohort studies have now been used in worldwide and European health impact assessment exercises, which in turn have been subjected to cost benefit analyses in support of PM policy development. Both in the U.S. and Europe, PM regulations are being updated in 2006. Also, the World Health Organization is preparing Air Quality Guidelines for worldwide application for the first time. At the conference, a brief overview will be given of the most recent decisions and proposals.

Biography: Dr. Bret Brunekreef is professor of environmental epidemiology and director of the Institute for Risk Assessment Sciences at Utrecht University. Since 2000, he has headed the Environmental and Occupational Health Division of the newly formed Institute for Risk Assessment Sciences (IRAS) at the Utrecht University. Recently, the Institute for Risk Assessment Sciences has absorbed the Department of Food Safety and Veterinary Public Health. Dr. Brunekreef became director of IRAS as of January 1, 2005.

On several occasions, Dr. Brunekreef served as advisor on national and international panels in the field of environmental health, including the Dutch National Health Council, of which he is a member, WHO and the U.S. EPA. Dr. Brunekreef is co-author of more than 200 peer reviewed journal articles in the field of environmental epidemiology and exposure assessment.

Friday, September 15, 2006
8:00 a.m. – 9:15 a.m.
Primary Versus Secondary and Biogenic Versus Anthropogenic
Organic Aerosol: Grand Challenges in Atmospheric Aerosol Research
Urs Baltensperger

Organic aerosol is either emitted as primary aerosol or formed in the atmosphere as secondary aerosol from gaseous precursors. In both cases, biogenic as well as anthropogenic sources contribute to the overall aerosol loading. Recent developments have substantially improved our understanding in this respect. As an example, carbon-14 analysis is able to distinguish fossil from biogenic carbon.
Combined with a discrimination of the water soluble and water insoluble fractions this method offers a great potential in tackling the above challenges. Concerning secondary organic aerosol, the polymerization (or rather oligomerization) processes recently found in simulation chamber experiments have triggered extensive research all over the world. As a result of this oligomerization, larger molecules with a lower vapor pressure are formed. This results in higher yields of secondary organic aerosol, with different chemical and physical features. This in turn may induce substantial changes in the health and climate impact of the atmospheric aerosol. New and innovative interdisciplinary research has a great potential in further improving our knowledge in this exciting field of research.

Biography: Urs Baltensperger is currently head of the Laboratory of Atmospheric Chemistry, Paul Scherrer Institut in Switzerland and a lecturer at ETH Zurich. He studied chemistry at the University of Zurich. Since his PhD thesis, he has been interested in aerosol research, focusing on physical and chemical aerosol characterization, heterogeneous chemistry, and aerosol effects on climate. He is chairman of the Scientific Advisory Group for Aerosol of the Global Atmosphere Watch program of the World Meteorological Organization (WMO), and president of the Commission for Atmospheric Chemistry and Physics of the Swiss Academy of Natural Sciences. He received the Professor Dr. Vilho Vaisala Award of WMO in 2003. He is author or co-author of more than 130 peerreviewed papers and has supervised about 20 PhD theses.