Aerosol Dosimetry Research Needs

Inhalation Toxicology, 18:841–843, 2006 c Taylor and Francis Group, LLC Copyright ISSN: 0895-8378 print / 1091-7691 online DOI: 10.1080/08958370600748778 Aerosol Dosimetry Research Needs Robert F. Phalen Department of Community and Environmental Medicine, University of California, Irvine, California, USA Mark D. Hoover Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA The October 2005 Frontiers in Aerosol Dosimetry Research Conference brought together 95 experts representing 53 orga- nizations from 12 different countries to discuss the state of the art in estimating internal doses from inhaled aerosol particles and gases. About one-third of the conference participants were from universities, one-third from commercial firms, and one- third from government/national laboratories, consulting firms, and other entities. At the end of the 2-day meeting, which was held at the Beckman Center of the National Academies on the University of California, Irvine, campus, attendees were invited to submit written suggestions for high-priority research. More than 50 suggested projects were submitted and the suggestions have been grouped into 32 specific topics covering four broad categories. An edited summary of the suggestions is provided here, starting with those topics most often noted. These sug- gestions are simply a snapshot of the priorities of individual scientists, and do not carry the approval of any regulatory or funding agency. DEVELOPMENT AND VALIDATION OF DOSIMETRY MODELS Although existing aerosol deposition models are impressive in their mathematical elegance and ability to provide useful dose predictions, many suggestions were offered that related to their improvement: Received 20 March 2006; accepted 22 March 2006. The conference was financially supported by the University of California Tobacco-Related Disease Research Program (TRDRP grant 13ST-0176), the University of California, Irvine Office of Research and Graduate Studies (award CSP-2004-2005-5), and the Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health (order 200-2005-M-13183). The findings and con- clusions in this document have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy. Susan Akhavan provided administrative, editorial, and manuscript prepara- tion services. This brief report represents an attempt to accurately in- tegrate and present more than 50 written suggestions, many of which overlapped. Of necessity, most of the suggestions have been edited in the interest of clarity and uniformity of style. The authors thank the participants for their contributions and apologize for any inaccuracies or possible distortion of the intent of those who submitted suggestions. Address correspondence to Robert F. Phalen, Air Pollution Health Effects Laboratory, Department of Community and Environmental Medicine, University of California, Irvine, CA 92697-1825, USA. E-mail: rfphalen@uci.edu 1. Scrutinize past and present particle deposition, retention, and clearance models to identify needs for improvement and a logical sequence for developing and validating new models. 2. Study the fundamental theories of particle deposition (in- cluding phenomena such as evaporation and bulk behavior) and evaluate the alternative approaches for their ability to explain observations. 3. Analyze the basic phenomena responsible for the deposition of inhaled particles (including factors such as flow instability and particle dynamics), especially for the submicrometer, noninertial regime. 4. Ascertain what is known and what is unknown regarding ob- taining correct dose assessments (not just particle deposition predictions), including any special retention or clearance is- sues for nanoparticles. 5. Improve physical simulations of particle deposition in the respiratory tract to provide more realistic physiological con- ditions. Such simulations should include modeling all re- gions of the respiratory tract in an integrated fashion, from the nares to distal alveoli, instead of focusing on isolated regions. 6. Establish a scientific basis for determining the relative im- portance of model parameters and how the key model pa- rameters and models can be validated. 7. Develop better physical (hollow) models of all of the airways and establish experimental designs and proto- cols for their validation with respect to in vivo particle inhalation. 8. Validate the predictions of lobar particle deposition models.