| Particle Concentrations in Urban Microenvironments Jonathan I. Levy,1 E. Andres Houseman,2 Louise Ryan,2 Dejuran Richardson,2 Students from the 1998 Summer Program in Biostatistics,* and John D. Spengler1 1Department of Environmental Health; 2Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA Abstract
Although ambient particulate matter has been associated with a range of health outcomes, the health risks for individuals depend in part on their daily activities. Information about particle mass concentrations and size distributions in indoor and outdoor microenvironments can help identify high-risk individuals and the significant contributors to personal exposure. To address these issues in an urban setting, we measured particle count concentrations in four size ranges and particulate matter  10 µm (PM10) concentrations outdoors and in seven indoor microenvironments in Boston, Massachusetts. Particle counts and PM10 concentrations were continuously measured with two light-scattering devices. Because of the autocorrelation between sequential measurements, we used linear mixed effects models with an AR-1 autoregressive correlation structure to evaluate whether differences between microenvironments were statistically significant. In general, larger particles were elevated in the vicinity of significant human activity, and smaller particles were elevated in the vicinity of combustion sources, with indoor PM10 concentrations significantly higher than the outdoors on buses and trolleys. Statistical models demonstrated significant variability among some indoor microenvironments, with greater variability for smaller particles. These findings imply that personal exposures can depend on activity patterns and that microenvironmental concentration information can improve the accuracy of personal exposure estimation. Key words: air pollution, exposure assessment, indoor air, microenvironments, particulate matter. Environ Health Perspect 108:1051-1057 (2000) . [Online 16 October 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p1051-1057levy/ abstract.html Address correspondence to J.I. Levy, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115 USA. Telephone: (617) 432-4845. Fax: (617) 432-4122. E-mail: jilevy@hsph.harvard.edu *B. Acosta-Garcia (University of Puerto Rico) , M. Cote (Harvard/Main Program for Children) , T. Jones (LeMoyne-Owen College) , R. Moore (Bennett College) , M. Price (Albany State University) , R. Sebro (Morehouse College) , K. Taylor (Hampton University) , and I. Williams (Howard University) . We thank H. Özkaynak for providing valuable feedback, and we are indebted to all of the Summer Program students for their interest and assistance. Funding for this research was provided in part by the National Cancer Institute (CA48061) , NIH (R25 GM55353) , U.S. EPA Cooperative Agreement CR825267-01, Task Order No. 0011 of the U.S. EPA HEEMR contract (68-D-99-011) , and by a U.S. EPA EMPACT grant. In addition, students in the Summer Program in Biostatistics were supported by NIEHS (5 T35 ES07293-05) . This paper has not been subjected to review by the above agencies and does not necessarily reflect their views. Received 17 April 2000 ; accepted 5 July 2000. Correction made on 23 October 2000.
The full version of this article is available for free in HTML or PDF formats. |
