Predictors of Endotoxin Levels in U.S. Housing Peter S. Thorne,1 Richard D. Cohn,2 Deepak Mav,2 Samuel J. Arbes Jr.,3,* and Darryl C. Zeldin3 1Environmental Health Sciences Research Center, College of Public Health, University of Iowa, Iowa City, Iowa, USA; 2Constella Group, LLC, Durham, North Carolina, USA; 3Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA Abstract Background: The relationship of domestic endotoxin exposure to allergy and asthma has been widely investigated. However, few studies have evaluated predictors of household endotoxin, and none have done so for multiple locations within homes and on a national scale. Objectives: We assayed 2,552 house dust samples in a nationwide study to understand the predictors of household endotoxin in bedroom floors, family room floors, beds, kitchen floors, and family room sofas. Methods: Reservoir house dust from five locations within homes was assayed for endotoxin and demographic and housing information was assessed through questionnaire and onsite evaluation of 2,456 residents of 831 homes selected to represent national demographics. We performed repeated-measures analysis of variance (rANOVA) for 37 candidate variables to identify independent predictors of endotoxin. Meteorologic data were obtained for each primary sampling unit and tested as predictors of indoor endotoxin to determine if wetter or warmer microclimates were associated with higher endotoxin levels. Results: Weighted geometric mean endotoxin concentration ranged from 18.7 to 80.5 endotoxin units (EU) /mg for the five sampling locations, and endotoxin load ranged from 4,160 to 19,500 EU/m2. Bivariate analyses and rANOVA demonstrated that major predictors of endotoxin concentration were sampling location in the home, census division, educational attainment, presence of children, current dog ownership, resident-described problems with cockroaches, food debris, cockroach stains, and evidence of smoking observed by field staff. Low household income entered the model if educational attainment was removed. Conclusion: Increased endotoxin in household reservoir dust is principally associated with poverty, people, pets, household cleanliness, and geography. Key words: allergens, asthma triggers, endotoxin, house dust, housing characteristics, indoor air, lipopolysaccharide, microorganism-associated molecular pattern, predictive model, reservoir dust. Environ Health Perspect 117:763–771 (2009) doi:10.1289/ehp.11759 available via http://dx.doi.org/ [Online 16 October 2008] Address correspondence to P.S. Thorne, Department of Occupational and Environmental Health, University of Iowa, College of Public Health, 100 Oakdale Campus, 176 IREH, Iowa City, IA 52242-5000 USA. Telephone: (319) 335-4216. Fax: (319) 335-4006. E-mail: peter-thorne@uiowa.edu Supplemental Material is available online at http://www.ehponline.org/members/2008/11759/suppl.pdf *Current address: Rho, Inc., Chapel Hill, NC. We thank R. Jaramillo and P. Crockett for statistical analyses and K. Kulhankova for endotoxin assays. This work was supported by National Institute of Environmental Health Sciences (NIEHS) grant P30 ES05605, U.S. Department of Housing and Urban Development’s Office of Healthy Homes and Lead Hazard Control, and the Intramural Research Program of the NIEHS, National Institutes of Health. The authors declare they have no competing financial interests. Received 4 June 2008 ; accepted 14 October 2008. The full version of this article is available for free in HTML or PDF formats. |