The relationships between personal PM exposures for elderly populations and indoor and outdoor concentrations for three retirement center scenarios

Personal exposures, indoor and outdoor concentrations, and questionnaire da ta were collected in three retirement center settings, supporting broader p articulate matter (PM) -health studies of elderly populations. The studies varied geographically and temporally, with populations studied in Baltimore , MD in the summer of 1998, and Fresno, CA in the winter and spring of 1999 . The sequential nature of the studies and the relatively rapid review of t he mass concentration data after each segment provided the opportunity to m odify the experimental designs, including the information collected from ac tivity diary and baseline questionnaires and influencing factors (e.g., hea ting, ventilation, and air-conditioning (HVAC) system operation, door and w indow openings, air exchange rate) measurements. This paper highlights both PM2.5 and PM10 personal exposure data and interrelationships across the th ree retirement center settings, and identifies the most probable influencin g factors. The current limited availability of questionnaire results, and c hemical speciation data beyond mass concentration for these studies, provid ed only limited capability to estimate personal exposures from models and a pportion the personal exposure collections to their sources. The mean perso nal PM2.5 exposures for the elderly in three retirement centers were found to be consistently higher than the paired apartment concentrations by 50% t o 68%, even though different facility types and geographic locations were r epresented. Mean personal - to - outdoor ratios were found to 0.70, 0.82, a nd 1.10, and appeared to be influenced by the time doors and windows were o pen and aggressive particle removal by the HVAC systems. Essentially identi cal computed mean PM2.5 personal clouds of 3 mug/m(3) were determined for t wo of the studies. The proposed significant contributing factors to these p ersonal clouds were resuspended particles from carpeting, collection of bod y dander and clothing fibers, personal proximity to open doors and windows, and elevated PM levels in nonapartment indoor microenvironments.