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RESPIRATORY DOSE TO SUSCEPTIBLE POPULATIONS ASSESSED BY EXPOSURE AND DOSIMETRY STUDIES
Citation:
KIM, C. S. AND R. W. WILLIAMS. RESPIRATORY DOSE TO SUSCEPTIBLE POPULATIONS ASSESSED BY EXPOSURE AND DOSIMETRY STUDIES. Presented at American Thoracic Society Annual Meeting, San Francisco, CA, May 18 - 23, 2007.
Description:
Respiratory Dose to Susceptible Populations Assessed by Exposure and Dosimetry Studies
Chong Kim1 and Ronald Williams2, 1USEPA National Health and Environmental Effects Research Laboratory and 2USEPA National Exposure Research Laboratory, RTP, NC.
Rationale: Particulate matter (PM) in the air is known to cause adverse health effects, particularly in elderly subjects with respiratory and cardiopulmonary disease. Although observed health effects are likely caused by multiple factors, the respiratory dose is one factor of particular concern because the morphological and physiological changes of the lung can alter deposition characteristics of inhaled particles. Methods: We examined recent exposure and dosimetry studies to determine how these two types of studies can be interlinked to better explain the risks of PM exposure, particularly for susceptible populations. Exposure data were obtained from the recent Seattle studies (EHP, 2003) comparing personal PM2.5 exposure among four different cohorts, healthy elderly subjects, elderly with coronary heart disease, elderly with chronic obstructive pulmonary disease (COPD), and children with asthma. In dosimetry studies we measured lung deposition of ultrafine, fine and coarse particles in four different subject groups, healthy young and elderly subjects, subjects with asthma and COPD, at various breathing patterns. Results: The personal exposure was similar for the healthy elderly and two sick elderly cohorts. Thus, exposure per se may not be a contributing factor for adverse health effects observed in elderly patients. There was no difference in lung deposition between the healthy young and elderly groups for all particle sizes tested, indicating that age is not a contributing factor for lung deposition. Total lung deposition in subjects with asthma and COPD, however, was greater than in healthy subjects under the same exposure conditions. Deposition was greater particularly in the proximal bronchial airways but was the same or lower in deep lung regions in patient groups compared with healthy subjects. Conclusions: Exposure alone is not a sufficient factor for assessing risk because some subjects can receive enhanced lung deposition under the same exposure conditions. An integrated measurement of exposure and internal dose among different subject groups will help better assess the risk associated with PM. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.